methodology of air pollution control

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Managing Air Quality - Control Strategies to Achieve Air Pollution Reduction

A control strategy related to air quality is a set of specific techniques and measures identified and implemented to achieve reductions in air pollution to attain an air quality standard or goal.

On this page:

Considerations in Designing an Effective Air Quality Control Strategy

Controlling sources of pollution.

• Need for Controls Applied Regionally or Nationally in Addition to Locally

What are the Steps in Developing a Control Strategy?

• Environmental: factors such as ambient air quality conditions, relevant meteorological conditions, location of the emissions source, noise levels, and any ancillary pollution from the control system itself.
• Engineering: factors such as pollutant characteristics (such as abrasiveness, reactivity and toxicity), gas stream characteristics, performance characteristics of the control system, and adequate utilities (for example, water for wet scrubbers).
• Economic: factors such as capital cost, operating costs, equipment maintenance, equipment lifetime, and administrative, legal, and enforcement costs.
• The U.S. Environmental Solutions Toolkit  is a user-friendly database that highlights scientific analysis, regulatory structures, and some examples of U.S. companies offering relevant solutions.
• Learn more about Export Promotion at EPA .

Pollution prevention approaches  to reduce, eliminate, or prevent pollution at its source, should be considered. Examples are to use less toxic raw materials or fuels, use a less-polluting industrial process, and to improve the efficiency of the process.  

The Clean Air Technology Center serves as a resource on air pollution prevention and control technologies, including their use, effectiveness and cost. Examples are mechanical collectors, wet scrubbers, fabric filters (baghouses), electrostatic precipitators, combustion systems (thermal oxidizers), condensers, absorbers, adsorbers, and biological degradation.

Controlling emissions related to transportation can include emission controls on vehicles as well as use of cleaner fuels.

Economic incentives , such as emissions trading, banking, and emissions caps can be used. These strategies may be combined with the "command-and-control" type regulations which have traditionally been used by air pollution control agencies.

Need for Controls Applied Regionally or Nationally in Addition to Locally

Air pollution does not recognize geographic boundaries.  Some pollutants can travel great distances affecting air quality and public health locally, regionally, nationally, and even internationally in areas that are downwind.

For this reason, control strategies to improve air quality in local areas need to include control measures that are mandated and implemented on a state, region-wide or national basis. In general, regulations established by the national government tend to have the widest application, which can minimize boundary and economic competition issues.

In the United States, the Clean Air Act requires that each state’s implementation plan contain provisions to prevent the emissions from the facilities or sources within its borders from contributing significantly to air quality problems in a downwind state. Learn more about the approach in the United States to address interstate air pollution transport .

• Determine priority pollutants. The pollutants of concern for a specific location will be based on the nature of the associated health or environmental effects and the severity of the air quality problem in that area.                                                                                                                                                                                                   
• Identify measures to control sources of pollution.                                                                                                                                                                                                                          
• Develop a control strategy and plan that incorporates the control measures. The written plan should include implementation dates. The plan will need to reference the requirements that owners or operators of emission sources will need to undertake to reduce pollution contributing to the air quality problems.                                                                                                                                                                                                                                                                                                          
• Involve the public. Invite input from the regulated community and others, including the general public when developing the control strategy. This early consultation reduces later challenges and can help streamline implementation.                                                                                                                                                            
• Incl ude compliance and enforcement programs.  These programs are very important to include and help owners or operators of sources understand the requirements, as well as the actions that environmental authorities can take if the sources don’t comply. 

​ Governments getting started in managing air quality should focus first on obvious sources of air pollution and the quickest means of controlling air emissions. More sophisticated and comprehensive strategies can be developed over time. The goal for all control strategies is to achieve real and measurable air emission reductions.

In the United States, control strategies to meet and maintain the national ambient air quality standards are developed by state governments. State governments adopt control measures through their legislative process and include them in state implementation plans, which need to be submitted and approved by EPA. The control measures are described and included in the plan.  Control measures that are part of an approved state implementation plan can be enforced by either the state or the national government.

Learn more regarding  basic information about air quality state implementation plans  and about  air quality implementation plans .

Learn more about how c ost analysis models and tools for air pollution regulations   support the assessment of emission reductions and engineering costs for air pollution control strategies.

Learn more about reducing emissions of hazardous air pollutants  and a ddressing stationary sources of air pollution  in the United States .

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Monitoring air pollution levels is key to adopting and implementing WHO's Global Air Quality Guidelines

New report summarizes air quality monitoring methods to estimate air pollution exposure.

• Environmental risks cause 12% of the global burden of disease, with air pollution ranking first.
• In 2021, WHO issued updated and more stringent air quality guidelines to reflect adverse health effects at lower concentrations than previously recognized.
• Air quality monitoring is the first step for understanding a population’s exposure and taking action.
• Report provides an overview of the strengths and weaknesses of different measurement and modelling methods.

“Air Pollution is a major public and environmental health issue with serious threats to people’s wellbeing and our environment,” says Dr Maria Neira, Director, Department of Environment, Climate Change and Health, WHO .  “Health impact assessment of air pollution and related interventions is the foundation for tackling air pollution efficiently, seriously and sustainably. This new report is key in supporting countries to get local data and measure air pollution exposure to protect people from the adverse impacts of dirty air.”

Data is key to tackle air pollution globally

Every year, 7 million people die prematurely from exposure to air pollution. At the foundation of this mortality figure ( SDG indicator 3.9.1 ) is the global estimate of ambient (or outdoor) air pollution exposure ( SDG Indicator 11.6.2 ). This indicator is obtained from a global model, the Data Integration Model for Air Quality (DIMAQ), whose accuracy relies on the availability of local reference-grade monitors, which are a critical part of a comprehensive air quality management programme. In addition to their accuracy, reference-grade monitors enable the monitoring of long-term air pollution exposures that are critical for health studies and the evaluation of interventions or sectoral policies. They are also crucial for the objective evaluation of compliance with standards. Ideally, every country should have access to at least one reference-grade monitor, which open the door to many other air quality measurement methods.   

Applicable to countries at different stages of development

While it is important to start somewhere, countries should balance their national priorities with available resources and employ a mixture of approaches to best address their air quality problems. Pivotal to the success of any air quality management programme is the awareness of the advantages and disadvantages of each approach: cost, technical complexity, outputs and the recognition that some methods require the prior presence of other measurement methods to be useful.  

Synthesizing the knowledge of global experts from the Global Air Pollution and Health Technical Advisory Group , the new report , Overview of methods to assess population exposure to ambient air pollution , presents a comparison of the strengths and weaknesses of individual measurement and modelling approaches. In addition, the publication highlights emerging methods such as machine learning and geostatistical data fusion methods, which combine air quality measurements and simulation modelling into a statistical model. The methods highlighted can be used locally, provincially and nationally to monitor multiple air pollutants and track progress resulting from air pollution reduction policies.

Report can be accessed by a wide audience

  Policy-makers and government officials can use the report to assess their country’s baseline air quality levels as well as to develop plans for air quality monitoring and data management. National and local authorities responsible for protecting public health can leverage its content in their fight against the adverse effects of air pollution. Additionally, low- and middle-income countries can find methods to assess their population exposure to air pollution that are best suited to their country’s social, economic and environmental conditions.

 However, no single monitoring method can address the entirety of a country’s air quality problem, and nations may want to employ a mixture of measurements and modelling methods to address their local air quality issues while balancing their national priorities and resource availability. Ultimately, multiple methods are needed for a comprehensive air quality management knowledge base and capability. Countries are encouraged to use as many of these approaches as needed, based on their circumstances and capabilities.

Media Contacts

Nada Osseiran

Communications Officer WHO

Mr. Paul Safar

Communications Support WHO

New Report: Overview of methods to assess population exposure to ambient air pollution

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Air Pollution Control

A section of Atmosphere (ISSN 2073-4433).

Section Information

Air pollution control constitutes a variety of means employed to limit damage done to the atmosphere by the discharge of harmful substances and energies. A control strategy is a set of specific techniques and measures identified and implemented to achieve reductions in air pollution to attain an air quality standard or goal. This section discusses air pollution control strategies, engineering, and technologies, including the performance, potential, and limitations of the major control processes. We also critically discuss flare processes, thermal oxidation, catalytic oxidation, gas-phase activated carbon adsorption, and gas-phase biofiltration as well as the design, installation, and operation of air pollution process equipment.

• electrostatic precipitators;
• baghouse filters;
• absorption;
• electrostatic precipitation;
• wet/dry scrubbing and packed scrubbers;
• flue gas desulfurization;
• gas catalysis reaction/catalyst;
• catalytic converters for VOC emission control;
• regenerative thermal oxidizer and thermal recuperative oxidizer for VOC abatement;
• rotary concentrator for high air volume low VOC concentration processes;
• particulate filters;
• evaporative emission controls;
• crankcase emission controls;
• thermal management strategies;
• engine and fuel management;
• enhanced combustion technologies;
• sensor technologies;
• GHG emissions reduction technologies;
• alternative fuel sources;
• urban motor vehicle pollution control.

Following special issues within this section are currently open for submissions:

• Recent Developments in Carbon Emissions Reduction Approaches (Deadline: 10 June 2024 )
• Urban Air Pollution Control and Low-Carbon Development (Deadline: 30 June 2024 )
• Engine Emissions: Assessment and Control (Deadline: 12 July 2024 )
• Bioindicators in Air Pollution Monitoring (Deadline: 31 July 2024 )
• CO 2 Geological Storage and Utilization (2nd Edition) (Deadline: 31 July 2024 )
• Characteristics and Source Apportionment of Urban Air Pollution (Deadline: 31 July 2024 )
• Recent Advances in Mobile Source Emissions (2nd Edition) (Deadline: 23 August 2024 )
• Advances in CO 2 Capture and Absorption (Deadline: 28 August 2024 )
• Advances in Source Tracing and the Control of Ozone and Its Precursors (Deadline: 16 September 2024 )
• Gas Emissions in Agriculture (Deadline: 27 September 2024 )
• Air Pollution Control in China: Progress, Challenges, and Perspectives (2nd Edition) (Deadline: 27 September 2024 )
• Characteristics and Control of Particulate Matter (Deadline: 30 November 2024 )
• Transport, Transformation and Mitigation of Air Pollutants (Deadline: 30 November 2024 )
• Catalytic Oxidation of Volatile Organic Compounds (Deadline: 30 November 2024 )
• Understanding Aerosol Filtration: Current Status and Future Directions (Deadline: 27 December 2024 )

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5 Effective Air Pollution Prevention Strategies

Every year, air pollution prematurely kills about seven million people worldwide. It is also one of the biggest threats to human health, increasing the risk of chronic heart and pulmonary diseases, lung cancer, stroke, and respiratory infections. What’s more, air pollution is contributing to the climate crisis and accelerating global warming. Governments urgently need to commit to air pollution prevention in an effort to solve one of the direst environmental problems in the world right now. As we celebrate the International Day of Clean Air for Blue Skies, which every year falls on September 7, we reflect on some of the most promising solutions to air pollution out there.

Sometime between 1820 and 1840, the world began transitioning to new manufacturing processes that became known as the Industrial Revolution. While this represented a turning point in the history of technological advancement and moulding the world as we know it today, industrialisation came at a huge cost for the environment and affected worldwide air quality, especially in new, developing urban areas. Even today, the highest levels of air pollution are recorded in cities. Six of the world’s 10 most polluted cities in 2021 were in India, with Bhiwadi topping the list, while neighbouring countries like Pakistan and Bangladesh are also some of the worst affected. In China, despite the huge progress made in recent years, where particulate pollution saw a 29% drop globally, 1.25 million people still die prematurely from pollution-related diseases every year.

The world has made remarkable advancements in air pollution reduction technologies and an increasing number of countries around the world have pledged to end all emissions in the coming decades. We explore the main drivers and effects of air pollution on the environment before diving deep into some of the best strategies for air pollution prevention.

Drivers of Air Pollution

Air pollution refers to the release of chemicals and pollutant particles into the air, mainly through human activities. Among the biggest contributors are fossil fuels. Global demand for oil, natural gas, and coal continues to increase despite calls to end our dependence on these energy sources in order to meet net-zero emissions goals. In 2021, global energy-related emissions reached a staggering 36.3 billion tonnes of CO2, their highest-ever level. 40% of which came from coal – soaring to an all-time high of 15.3 billion tonnes – followed by 10.7 billion tonnes from oil, and 7.5 billion tonnes from natural gas. 

Another driver is ozone, a toxic gas that turns into smog – an extremely harmful form of air pollution – when it reaches too close to the ground, significantly reducing visibility. Extreme climate events like dust storms as well as changing weather conditions are also responsible for poisoning the atmosphere. For example, high air pressure and heat waves can create stagnant air where pollutants usually concentrate in large quantities. Extreme heat waves also increase the risks of large-scale wildfires, notorious for releasing more carbon emissions, smog, and pollutants into the air. 

Effects of Air Pollution on the Environment

Apart from causing millions of premature deaths and illnesses – especially in low-income countries like South and East Asia – there is growing evidence among the scientific community that air pollution can have detrimental impacts on other aspects of human health and wellbeing – such as their cognitive function. Several studies have found that polluted air often impedes or lowers the cognitive ability of those frequently exposed to it. 

But air pollution does not only impact humans. Its environmental effects are also vast and worrying. They range from acid rain – which is extremely harmful to the soil and plants – to birth defects, reproductive failure, and diseases among wildlife animals. Highly polluted rain can also compromise agriculture, as it makes crops more vulnerable to diseases from increased UV radiation caused by ozone depletion. 

You might also like: History of Air Pollution: Have We Reached A Point of No Return?

Air Pollution Prevention

While we know much about the causes and effects of air pollution, there is still much to be done in terms of prevention. To understand how governments can tackle the problem, it is useful to have a look at the main sectors contributing to global greenhouse gas emissions. Indeed, the only ways to drastically reduce air pollution are to adopt a wide range of policies that regulate all polluting industries – from energy production to transportation and agriculture – as well as to reflect on broader solutions such as carbon tax systems. 

Figure 1: World’s Most Polluting Sectors, 2020

1. Cut Down Emissions from Power Plants

One obvious but effective strategy to cut down emissions is to phase out fossil fuels immediately, yet it has proven to be difficult to implement. As the latest IPCC climate report clearly stated, in the race to reach net-zero emissions, there is no room for any fossil fuel developments . Shifting to other energy sources like nuclear and renewables is a long and complicated process that requires global coordination and collaboration. Yet, not all countries are on board and while some are slowly making the transition, others have no intentions of phasing out fossil fuels. 

In the meantime, countries like the US are implementing strategies to hold power plants accountable for their pollution. For example, in March 2022, the Environmental Protection Agency (EPA) unveiled the “Good Neighbor” plan to cut interstate smog pollution from power stations by requiring them to operate their pollution control equipment and keep their daily emissions under a pre-established limit. 

2. Decarbonise the Global Transport Sector

Transport accounts for 8 billion tonnes – or approximately one-fifth – of global carbon dioxide emissions. These are expected to grow significantly over the next 30 years as a result of increasing transport demand.

Figure 2: Global CO2 Emissions from Transport, 2018

According to the EPA, there are three methods to reduce greenhouse gas emissions from transportation. The first is to increase the efficiency of vehicle technology. A good start – according to a report by the United Nations – is developing weight reduction and improvements to engines and tires that can make vehicles more fuel-efficient, reduce their reliance on oil, and cut expenses.

One of the most important technologies we have to decarbonise the transport sector is electric vehicles (EV). Significant progress has been made in this industry and costs of batteries have declined by 90% in recent years. Despite EVs being a much better alternative than fossil fuel vehicles, as the latter generate much higher emissions over their lifetime, the electrification of the transportation sector has a dark side. Producing EV batteries requires greater resource extractivism , which has substantial destructive consequences for the environment and local communities, an aspect of this industry that cannot be ignored. Fortunately, EV companies are building a much more sustainable supply chain by improving the efficiency and lifespan of batteries, researching a way to build them using other resources as well as recycling old batteries to reuse raw materials.

But switching to EVs is not the only option we have. We can lower transportation’s carbon footprint by changing how we travel – for example, opting for public transport and car-sharing – as well as how we transport goods around the world. Emissions from the global supply chain have reached historic heights. In 2020, the shipping and return of products within the e-commerce industry alone accounted for 37% of the total GHG emissions , attributing to the unsustainable habits of modern consumers and their appetite for convenience. It is estimated that by 2030, the number of delivery vehicles will increase by 36%, reaching approximately 7.2 million vehicles . This will not only result in an increase of about 6 million tonnes of CO2 emissions, but it will also increase commutes by 21%, as vehicles will take longer to travel due to higher traffic congestion. All things considered, the best way to drastically reduce the impact of the shipping industry is by rethinking the means of transport, for example by prioritising rail and marine vessels over truck drivers.

Emissions can also be reduced by using fuels with a minimal carbon footprint such as biofuels , renewable natural gas, hydrogen as well as sustainable aviation fuel . Lastly, it is the governments’ job to implement tighter fuel and vehicle emission standards. As part of its targets to reduce the net greenhouse gas emissions by 50% in 2030, the US has taken into account many sector-specific reduction pathways . The Biden administration is currently working on incentives for zero-emission personal vehicles, funding for charging infrastructure, and support for research in low carbon, new-generation renewable fuels. Simultaneously, sixteen states including California, New York, and Pennsylvania, are imposing their own pollution limits on cars . Similarly, the European Union is encouraging the production of greener vehicles and it has recently strengthened the CO2 standards for cars and vans as a way to facilitate its phase-out of internal combustion engines.

3. Adopt a More Sustainable Approach to Agriculture

Recent data from the Food and Agriculture Organization (FAO) shows that 31% of human-caused GHG emissions originate from the world’s agri-food systems. From the 16.5 tonnes generated in 2019, the largest share – 7.2 billion tonnes – came from within the farm gate, 5.8 billion tonnes from the supply-chain processes, while 3.5 billion tonnes from land use change. 

Thus, efforts to address the exploitation of resources like land and water as well as the promotion of sustainable agriculture are among the most crucial steps in air pollution prevention. A big issue related to soil depletion is the excessive use of fertilisers. Switching to nitrate-based solutions can be one of the easiest fixes in reducing farms’ impact on air pollution. Israel has made incredible technological advances and managed to reduce the overconsumption of water through drip irrigation , a system that delivers water and nutrients directly into the plant’s root through pipes. The technology is now being used in some African countries as well, thanks to funding from the World Bank. Lastly, countries like Australia have found ways to reduce agricultural methane emissions from farming by modifying the diets of livestock .

4. Introduce a Carbon Tax System

A carbon tax is an instrument of environmental cost internalisation, imposed on producers of raw fossil fuels based on the relative carbon content of those fuels. Governments usually set a fixed price that emitting companies must pay for each ton of greenhouse gas emissions they emit. 

So far, 27 countries have implemented a carbon tax system as a way to incentivise polluters to lower emissions or switch to more efficient processes and cleaner fuels. At the same time, the carbon tax is a great way to reduce air pollution and greenhouse gases generated from the same human activities and it is thus a good way to hit two birds with one stone .

5. Improving Air Quality While Fighting Climate Change

Last but not least, air pollution can be prevented by tackling climate change. These two phenomena are closely intertwined and neither can be seen exclusively as the cause or the effect. While deteriorating air quality is a consequence of climate change, air pollution also contributes to worsening global warming. That is why the climate crisis cannot be left out of the equation. Effective efforts to tackle climate change would significantly reduce deforestation and wildfires, two of the main sources of air pollution. Air quality and climate change are just one example of causes and effects overlapping. Therefore, the best shot for governments around the world to reduce air pollution is to implement broader policies that aim at tackling all aspects of the looming climate crisis.

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About the Author

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Wet scrubbers and packed scrubbers

Flue gas desulfurization, incineration, carbon sequestration.

Control of gases

Gaseous criteria pollutants, as well as volatile organic compounds (VOCs) and other gaseous air toxics , are controlled by means of three basic techniques: absorption , adsorption , and incineration (or combustion ). These techniques can be employed singly or in combination. They are effective against the major greenhouse gases as well. In addition, a fourth technique, known as carbon sequestration , is in development as a means of controlling carbon dioxide levels.

In the context of air pollution control, absorption involves the transfer of a gaseous pollutant from the air into a contacting liquid, such as water. The liquid must be able either to serve as a solvent for the pollutant or to capture it by means of a chemical reaction .

Wet scrubbers similar to those described above for controlling suspended particulates may be used for gas absorption. Gas absorption can also be carried out in packed scrubbers, or towers, in which the liquid is present on a wetted surface rather than as droplets suspended in the air. A common type of packed scrubber is the countercurrent tower. After entering the bottom of the tower, the polluted airstream flows upward through a wetted column of light, chemically inactive packing material. The liquid absorbent flows downward and is uniformly spread throughout the column packing, thereby increasing the total area of contact between gas and liquid. Thermoplastic materials are most widely used as packing for countercurrent scrubber towers. These devices usually have gas-removal efficiencies of 90–95 percent.

Cocurrent and cross-flow packed scrubber designs are also used for gas absorption. In the cocurrent design, both gas and liquid flow in the same direction—vertically downward through the scrubber. Although not as efficient as countercurrent designs, cocurrent devices can work at higher liquid flow rates. The increased flow prevents plugging of the packing when the airstream contains high levels of particulates. Cocurrent designs afford lowered resistance to airflow and allow the cross-sectional area of the tower to be reduced. The cross-flow design, in which gas flows horizontally through the packing and liquid flows vertically downward, can operate with lower airflow resistance when high particulate levels are present.

In general, scrubbers are used at fertilizer production facilities (to remove ammonia from the airstream), at glass production plants (to remove hydrogen fluoride), at chemical plants (to remove water-soluble solvents such as acetone and methyl alcohol ), and at rendering plants (to control odours).

Sulfur dioxide in flue gas from fossil-fuel power plants can be controlled by means of an absorption process called flue gas desulfurization (FGD). FGD systems may involve wet scrubbing or dry scrubbing. In wet FGD systems, flue gases are brought in contact with an absorbent, which can be either a liquid or a slurry of solid material. The sulfur dioxide dissolves in or reacts with the absorbent and becomes trapped in it. In dry FGD systems, the absorbent is dry pulverized lime or limestone ; once absorption occurs, the solid particles are removed by means of baghouse filters ( described above ). Dry FGD systems, compared with wet systems, offer cost and energy savings and easier operation, but they require higher chemical consumption and are limited to flue gases derived from the combustion of low-sulfur coal .

FGD systems are also classified as either regenerable or nonregenerable (throwaway), depending on whether the sulfur that is removed from the flue gas is recovered or discarded. In the United States most systems in operation are nonregenerable because of their lower capital and operating costs. By contrast, in Japan regenerable systems are used extensively, and in Germany they are required by law. Nonregenerable FGD systems produce a sulfur-containing sludge residue that requires appropriate disposal. Regenerable FGD systems require additional steps to convert the sulfur dioxide into useful by-products like sulfuric acid .

Several FGD methods exist, differing mainly in the chemicals used in the process. FGD processes that employ either lime or limestone slurries as the reactants are widely applied. In the limestone scrubbing process, sulfur dioxide reacts with limestone (calcium carbonate) particles in the slurry, forming calcium sulfite and carbon dioxide . In the lime scrubbing process, sulfur dioxide reacts with slaked lime (calcium hydroxide), forming calcium sulfite and water. Depending on sulfur dioxide concentrations and oxidation conditions, the calcium sulfite can continue to react with water, forming calcium sulfate ( gypsum ). Neither calcium sulfite nor calcium sulfate is very soluble in water, and both can be precipitated out as a slurry by gravity settling. The thick slurry, called FGD sludge, creates a significant disposal problem. Flue gas desulfurization helps to reduce ambient sulfur dioxide levels and mitigate the problem of acid rain . Nevertheless, in addition to its expense (which is passed on directly to the consumer as higher rates for electricity), millions of tons of FGD sludge are generated each year.

Gas adsorption , as contrasted with absorption, is a surface phenomenon. The gas molecules are sorbed—attracted to and held—on the surface of a solid. Gas adsorption methods are used for odour control at various types of chemical-manufacturing and food-processing facilities, in the recovery of a number of volatile solvents (e.g., benzene ), and in the control of VOCs at industrial facilities.

Activated carbon (heated charcoal ) is one of the most common adsorbent materials. It is very porous and has an extremely high ratio of surface area to volume. Activated carbon is particularly useful as an adsorbent for cleaning airstreams that contain VOCs and for solvent recovery and odour control. A properly designed carbon adsorption unit can remove gas with an efficiency exceeding 95 percent.

Adsorption systems are configured either as stationary bed units or as moving bed units. In stationary bed adsorbers, the polluted airstream enters from the top, passes through a layer, or bed, of activated carbon, and exits at the bottom. In moving bed adsorbers, the activated carbon moves slowly down through channels by gravity as the air to be cleaned passes through in a cross-flow current.

The process called incineration or combustion —chemically, rapid oxidation—can be used to convert VOCs and other gaseous hydrocarbon pollutants to carbon dioxide and water . Incineration of VOCs and hydrocarbon fumes usually is accomplished in a special incinerator called an afterburner. To achieve complete combustion, the afterburner must provide the proper amount of turbulence and burning time, and it must maintain a sufficiently high temperature. Sufficient turbulence, or mixing, is a key factor in combustion because it reduces the required burning time and temperature. A process called direct flame incineration can be used when the waste gas is itself a combustible mixture and does not need the addition of air or fuel.

An afterburner typically is made of a steel shell lined with refractory material such as firebrick . The refractory lining protects the shell and serves as a thermal insulator. Given enough time and high enough temperatures, gaseous organic pollutants can be almost completely oxidized, with incineration efficiency approaching 100 percent. Certain substances, such as platinum , can act in a manner that assists the combustion reaction. These substances, called catalysts , allow complete oxidation of the combustible gases at relatively low temperatures.

Afterburners are used to control odours, destroy toxic compounds , or reduce the amount of photochemically reactive substances released into the air. They are employed at a variety of industrial facilities where VOC vapours are emitted from combustion processes or solvent evaporation (e.g., petroleum refineries , paint-drying facilities, and paper mills ).

The best way to reduce the levels of carbon dioxide in the air is to use energy more efficiently and to reduce the combustion of fossil fuels by using alternative energy sources (e.g., nuclear , wind , tidal , and solar power ). In addition, carbon sequestration can be used to serve the purpose. Carbon sequestration involves the long-term storage of carbon dioxide underground, as well as on the surface of Earth in forests and oceans. Carbon sequestration in forests and oceans relies on natural processes such as forest growth. However, the clearing of forests for agricultural and other purposes (and also the pollution of oceans) diminishes natural carbon sequestration. Storing carbon dioxide underground—a technology under development that is also called geosequestration or carbon capture and storage—would involve pumping the gas directly into underground geologic “reservoir” layers. This would require the separation of carbon dioxide from power plant flue gases (or some other source)—a costly process.

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A Methodology of Assessment of Air Pollution Health Impact Based on Structural Longitudinal Modeling of Hierarchical Systems and Fuzzy Algorithm: Application to Study of Children Respiratory Functions

Friger, M; Bolotin, A; Peleg, R

Ben-Gurion University Of The Negev, Beersheba.

Introduction:

Assessing the effects of air-pollution is a significant problem in the field of modern environmental epidemiology. When modeling these effects it is important that the models must be epidemiologically meaningful and robust (that is, insensitive to variations in the model parameters). The objective of this paper is to propose a methodology for the assessment of the health impact of air pollution. The proposed methodology involves the construction of models for complex dynamic hierarchical systems in environmental epidemiology and their problem-oriented interpretation.

The principal stages of the proposed methodology are:

• Creation of a multivariate hierarchical structural model based on system analysis.
• Generation of a mathematical formalization for this model.
• Development of a statistical model for a particular study case based on the mathematical formalization, using the generalized estimating equations technique and time-series analysis. At this stage, for a dichotomized dependent variable, a special fuzzy algorithm was used. The algorithm employed fuzzy membership functions instead of the binary variable to obtain robust regression models.
• Use of the “multi-layered” approach for model interpretation developed by the authors. This approach involved the creation of special functional time-dependent coefficients that reflect the effect of air pollutants at a given time. These coefficients allow an epidemiological meaningful model interpretation. Thus, they can be used for air-pollution health effects assessment.

The proposed methodology was used to analyze data collected from lung function measurements in 165 children from February-September 2002 (about 4000 individual daily records). The subject variables were age, gender, body-mass index, and place of residency. The meteorological variables included daily maximum temperature, average humidity and barometric pressure. The air-pollutant variables were suspended particles, ozone, nitrogen and sulphur oxides. In addition, the effects were studied up to a 3-day lag. The results demonstrated a statistically significant effect of air-pollution on lung function. Changes in most of the pollutants did not cause a critical decrease in lung function. However, for the observed period, a 10 mkg/m 3 increase in ozone was associated with a mean decrease in lung function of 6 units for a one-day delay.

Discussion and Conclusions:

The assessment of the health effects of air pollution and their interpretation make epidemiological sense, lending support to the correctness of the proposed methodology. Testing the models by changing the dichotomization cutoff for the lung function variability shows that the models based on the proposed fuzzy algorithm are robust.

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• J Environ Health Sci Eng
• v.19(2); 2021 Dec

Urban air pollution control policies and strategies: a systematic review

Ahmad jonidi jafari.

1 Research Center for Environmental Health Technology, Iran University of Medical Sciences, Tehran, Iran

2 Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran

Esmail Charkhloo

Hasan pasalari.

A wide range of policies, strategies, and interventions have been implemented to improve air quality all over the world. This systematic review comprehensively appraises the policies and strategies on air pollutants controls enacted in different countries, worldwide. Three databases, Web of Science, PubMed and Scopus, were used for the search. After screening, a total of 114 eligible manuscripts were selected from 2219 documents for further analysis. Selected articles were divided into two categories: (1) articles focusing on introducing the policies and strategies enacted for controlling air pollution in different countries, and (2) articles which focused on different policies and strategies to control one or more specific pollutants. In the former one, urban air pollution control strategies and policies were divided into four categories, namely, general strategies and policies, transportation, energy, and industry. In case of latter category, policies and strategies focused on controlling six pollutants (PM, SO 2 , NO 2 , VOC S , O 3 and photochemical smog). The results indicated that, the most common policies and strategies enacted in most countries are pertinent to the transportation sector. Changing energy sources, in particular elimination or limited use of solid fuels, was reported as an effective action by governments to reduce air pollution. Overall, most policies enacted by governments can be divided into three general categories: (a) incentive policies such as implementing a free public transportation program to use fewer private cars, (b) supportive policies such as paying subsidies to change household fuels, and (c) punitive policies such as collecting tolls for cars to enter the congestion charging areas. Depending on the circumstances, these policies are implemented alone or jointly. In addition to the acceptance of international agreements to reduce air pollution by governments, greater use of renewable energy, clean fuels, and low-pollution or no-pollution vehicles such as electric vehicles play an important role in reducing air pollution.

Introduction

Nowadays, air pollution is known to be closely related to economic growth, population and energy consumption. There is a chain relation among the maintenance of economic development and improvement the living standards, population growth, increased demand for energy, and increasing the production and emission of air pollutants. Air pollution is considered as a serious issue; it causes different concern including climate changes, biodiversity reduction, affects crops and agricultural production and soil acidification [ 1 , 2 ]. According to WHO reports (2016), 4.2 million premature deaths were attributed to air pollution in both developed and developing countries; 91% premature deaths are observed in low- and middle-income countries including South-East Asia and Western Pacific regions [ 3 ]. The studies indicate that people living in low-level social-economic regions encountered with high level of air pollutants concentrations in ambient air [ 4 – 10 ]. A variety of diseases including respiratory diseases (asthma, bronchitis, pneumonia), different types of allergies, disturbances of the central nervous system, and circulatory problems are attributed to air pollution [ 11 – 17 ].

Road transportation are known as the main source for air pollution. In addition, domestic, commercial, and industrial activities may also cause air pollution. It is reported that more than 70–80% of air pollution in large cities in developing countries are attributed to greenhouse gas emissions from a large number of worn-out vehicles combined with poor vehicle maintenance, poor road structure, and poor fuel quality [ 18 – 24 ]. According to WHO report (2016), 91% of the world's population experienced the air with quality lower than the standard values [ 3 ]. The key air pollutants are: particulate matters (PM 2.5 and PM 10 ), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), carbon monoxide (CO), and (O 3 ) [ 25 ]. The major sources of air pollution, their corresponding health effects and standard values recommended are summarized in Table ​ Table1 1 .

Summary of the sources and limits or guidelines of the major air pollutants [ 26 – 29 ]

The basic and inherent advantages of establishment the legislations, strategies, and policies in the fields of air pollution are preventive measurement and requirement to control the air pollution in emission sources, improving the air quality and avoiding negative health outcomes. Air pollution control efforts dates back to more than a century. The Chicago legislation (1881), smoke abatement in Boston in the States of America (1910–1912) and Clean Air Act (1925) following “Great London Smog” in the UK are the earliest strategies for air pollution control [ 26 – 28 ]. However, afterwards, a series of legislations and programs have been enacted at the international level and some at the national and local levels. International actions such as the Paris Agreement (2015) recommend to the countries; it recommends governmental authorities to lower the increasing global warming and temperature below 2 °C and to in particular prevent dangerous impacts of climate change [ 29 , 30 ]. At the continental level, European Union (EU) Directives enacted the values guidelines for air pollutants and the convention on long-range trans-boundary air pollution (CLRTAP) and protocols related to emission reductions for specific air pollutants [ 31 , 32 ]. In case of local preventive air pollution actions, Prohibition of solid fuel use in homes, low emission zones (LEZs) and the introduction of vehicle exhaust catalysts (VECs) are the most common approaches [ 27 , 33 , 34 ].

The purpose of this study was to comprehensively cover the strategies and policies that governments have enacted to improve air quality or urban air pollution control. To the best of our knowledge, this is the first global systematic review on urban air pollution control policies and strategies with this number of countries; it can contribute to advance the knowledge in this field.

Search strategy

The present systematic review was performed according to standard methods the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) [ 35 ]. A comprehensive screening approach to find the urban air pollution control strategies and policies published in peer-reviewed journal was performed up to 19 January 2021 in three scientific databases: PubMed, Web of Science, and Scopus databases. The selected keywords included “air pollut*” OR “atmospheric pollut*” OR “air contaminant*” OR “polluted air” OR “air quality” OR “outdoor air pollut*” OR “ambient air pollut*” OR “atmospheric pollut*”AND “Control policy” OR “Control management” OR “Control strateg*” OR “intervention plan*”. Based on the exclusion and inclusion criteria, the most relevant articles were selected. The search was limited to the English language. We also searched the references lists of qualified articles and grey literature databases to find additional pertinent studies.

Study selection, eligibility criteria, and data extraction

Briefly, four sequential steps were performed to select the eligible manuscripts (Fig.  1 ). First, the selected manuscripts were entered into the EndNote X8. Second step was removing the duplicated studies. Third, the eligibility of articles were screened by the titles and abstracts of the remaining articles were reviewed for suitability. Fourth, the full texts of the potentially eligible manuscripts were evaluated to meet the aim of present systematic review. Finally, the selected study was throughoutly screened to meet the inclusion criteria mentioned in Table ​ Table2 2 The extracted data from the selected articles cover the following items: urban air pollution control policies and strategies, country, geographical location, start time or period time covered, authors' names, publication year, title, type of pollutant.

The screening process of articles

Inclusion and exclusion criteria for selection the eligible articles

Results and discussion

Characteristics of literature.

After removing the duplicates, 2219 documents remained for review based on titles and abstracts (Fig.  1 ). The full texts of 515 relevant documents were retrieved. Finally, 114 documents were selected according to inclusion criteria. The articles were divided into two categories. The first category articles include urban air pollution control strategies and policies based on geographical location (Table ​ (Table3), 3 ), the second category articles include urban air pollution control strategies and policies based on the type of pollutant (Table ​ (Table4). 4 ). Out of 114 final articles selected, 81 articles were placed in the first category and 33 articles in the second category.

Strategies and policies for urban air pollution control, categorized based on geographical locations

*The time period is cited in the Policies and Strategies column

**Stove and Chimney

Strategies and policies for urban air pollution control, categorized based on the type of pollutant

*The time period is cited in the policies and strategies column

**Stationary sources emission control program

***Vehicular pollution control plan

Characteristics of the retained studies

Table ​ Table3 3 summarizes the urban air pollution control strategies and policies based on geographical location. Among the 81 articles, the summarized number of studies performed for each country was as follows: China (n = 19), USA (n = 11), India (n = 7), Germany and Mexico (n = 4), the United Kingdom, Japan, Taiwan, and Hong Kong (n = 3), Italy, Turkey, Poland, Ireland, Egypt, and Chile (n = 2), Iran, Bhutan, New Zealand, Australia, Brazil, Wales, Norway, the Netherlands, Hungary, South Africa (n = 1), an article covered ten Asian countries and an article focused on the United Kingdom, New Zealand, Australia, States of America, Canada and the Netherlands.

Among 33 articles classified in second category, the summarized number of articles based on the type of pollutant in was as follows (see Table ​ Table4): 4 ): PM: China and Iran (n = 1); PM 10 : United Kingdom (n = 1); PM 2.5 : China (n = 3), and Brazil (n = 1); fine and coarse particles: India (n = 1); PM 2.5 -bound nickel (Ni): China (n = 1); [Particulate and lead: Egypt (n = 1); PM 10 and diesel soot: German (n = 1); Fine Dust: Korea (n = 1); Primary Particulate Matter, SO 2 , ROG and NO 2 : the United States (n = 1); SO 2 : China (n = 3), United States (n = 2), Japan (n = 1), and Japan–China (n = 1); NO 2 : China (n = 1); NO 2 : Korea (n = 1); VOCs: Hong Kong and Korea (1 each); O 3 : United States (n = 5), China and Spain (1 each); PM 2.5 and O 3 : China (n = 1); and photochemical smog: United States (n = 1).

A summary of planned urban air pollution control strategies and policies

Figure  2 shows the classification and categories of different air pollution control policies enacted in different countries. In general, the selected studies were classified in two categories: (1) studies focused on introduction the policies and strategies to control air pollution in different countries of the world, and (2) articles focused on different policies and strategies to control one or more specific pollutants.

Segmentation of urban air pollution control policies and strategies

In this section, urban air pollution control strategies and policies were classified into four categories, namely, general strategies and policies, transportation, energy, and industry.

General strategies and policies

The most important regulations, general strategies and policies to air pollution control enacted in different countries are as follows: (See Table ​ Table3 3 ).

Clean air action [ 48 – 50 ], clean air act (CAA) [ 27 , 72 , 86 , 98 , 114 ], air pollution control act (APCA) [ 55 ], Environmental Protection Law [ 102 ], the atmospheric pollution prevention act (APPA), Air Quality Act and the National Framework for Air Quality Management in South Africa [ 111 ], The Third Development Plan of Economy, Social and Cultural of the Country and Integrated Master Plan of Air Pollution Control [ 72 ], the Air Pollution Control Action Plan (APCAP) and 13th Five-Year Plan (13th FYP) [ 52 ], the Blue-Sky Defense War and Environmental Protection Tax Law [ 54 ], Comprehensive Action issued and Improve environmental law [ 48 – 50 ], Comprehensive Urban Air Quality Control Strategy [ 81 ], Air Quality Management Plan [ 84 ], Road Vehicles Act [ 69 ], Smoke and Soot Law, Establishment of the Basic Environmental Pollution Control and Establishment of the Air Pollution Control Act [ 70 ], the PCDD/PCDF Emission Standard for Municipal Solid Waste (MSW) Incinerators and Subsidize Local Governments to Accomplish Air Quality Improvement Programs [ 55 ], Expanding the Existing Smoky Vehicle Program [ 58 ], National Ambient Air Quality Standards (NAAQS) and Air Prevention and Control of Pollution Act [ 62 – 64 ], National Clean Air Program [ 65 ], the Comprehensive Survey on Air Pollution [ 61 ], the Clean Air Act Amendments [ 76 , 77 ], Clean Fuels Program [ 84 ], the low for open burning of waste (outdoor) [ 62 – 64 ].

Economic policies [ 36 , 48 – 50 ], economic incentive policy [ 69 ], reduce carbon emissions [ 53 ], reforestation program [ 33 ], restriction on use of DG (diesel generator) sets [ 68 ], distribution of educational leaflets [ 75 ], emissions tax [ 76 , 77 , 105 ], subsidy for expenditure on abatement capital [ 76 , 77 ], joint prevention and control of regional air pollution [ 51 ], reducing regional emission sources of gaseous pollutants [ 41 ], adjusting the economy to balanced development and industrialization and urbanization [ 42 ], strengthen government governance responsibilities and implement environmental supervision actions [ 54 ], SO 2 taxation [ 44 ], Prohibit all open burning [ 38 , 89 ], prohibition in “backyard” refuse burning [ 27 ].

Air pollution control regulations and policies have been enacted in many countries around the world; most cases had positive consequences. For example, in a study focused on the impact of the Blue-Sky Defense War law in China, a 14.49 and 23.43 μg m −3 reduction in the monthly average concentration of PM 2.5 and PM 10 were obtained [ 54 ]. Zhang et al. (year) showed that over the 40-year period in the UK, PM 2.5 and NO 2 - attributed mortalities were reduced by 56% and 44% respectively. While, the O 3 - attributable mortalities experienced an increase of 17% over the same period [ 115 ]. It has also been shown that the most effective way to control air pollution, especially greenhouse gases, is to accept and implement international agreements such as the Paris Agreement [ 116 ].

A preliminary analysis in the United States (1975) indicated that emissions tax and an increase in the gasoline tax were more effective than emission standards [ 77 ]. China in 2005 performed a comprehensive control policy in order to control the multiple pollutants (SO 2 , NO 2 , VOC and PM) emissions and emission sources in local and regional levels [ 51 ]. The results of study Streit in Mexico City showed that the prohibition of all open burning, implemented in 1993, significantly reduced CO, HCs, and NO 2 emission compared to other pollutants [ 89 ].

Strategies and policies related to transport

The most common measurements for air pollution control with special focus on transportation are divided into four categories: improving infrastructure and transportation structure, control measures on vehicles, fuel quality improvements and alternative fuels, and traffic restrictions.

Improving infrastructure and transportation structure .

The most important measures related to the improvement of infrastructure and transportation structure to control air pollution are as follows (See Table ​ Table3 3 ):

Improvement of road structure [ 69 ], adjustment the transportation structure and building a green transportation system [ 54 ], transportation mode modification [ 27 ], expansion of public transportation [ 87 , 113 ], public transport, improvement and promotion the public transport [ 36 , 62 – 64 ], allowing for temporary free public transport [ 34 ], phasing out of worn-out vehicles [ 33 , 67 ], Phasing out of worn-out Two-wheeled engines [ 67 ], retirement of older diesel trucks and buses in urban areas [ 71 ], elimination of motorcycles and substandard vehicles [ 43 ], retire old vehicles [ 48 – 50 ], elimination of “yellow-brand” vehicles [ 45 , 48 – 50 ], obsoleting vehicles with earlier emission standards [ 40 ], optimize the traffic control strategies [ 46 ], install enough numbers of parking meter [ 72 ], imposing higher parking fees [ 34 ], advanced vehicles [ 36 ], public awareness of traffic [ 72 ], make strict standards for new vehicles [ 48 – 50 ], temporal traffic control measure [ 36 , 48 – 50 ], control of imported cars [ 72 ], banning of imported used cars [ 61 – 64 ], electric vehicle incentive program [ 62 – 64 ], growth in rail transit infrastructure [ 39 ], construction of underground lines [ 72 ], expansion of the Subway [ 89 ].

Congestion is considered as one of the most important concern in large cities. Traffic congestion causes high costs, delays, and increased fuel consumption; it has unpleasant social and environmental consequences [ 117 ]. One of the most important policies and strategies related to transportation is recommendation for less use of private cars and more use of public transportation and bicycles. A study conducted by Rojas-Rueda, et al. in Barcelona (Spain) revealed that 40% decrease in car trips would prevent 10.03 deaths, due to a 0.64% reduction in exposure to PM 2.5 [ 118 ]. In San Francisco, some incentives are considered for the employers to less use of private cars, public transport use and bicycle uses; the people are given some subsides or pre-tax deductions of transport costs [ 119 ]. The establishment of subways in cities as a means of public transportation has a major impact on reducing air pollution. For instance, since 2005, Beijing has experienced a rapid growth in rail transportation infrastructure and improved air quality. The results showed that the operation of the rail transit system has a great effect on reducing most of the air pollutants concentrations (PM 2.5 , PM 10 , SO 2 , NO 2 , and CO), however, it has little effect on the reduction of O3 pollution [ 39 ]. Incentive programs such as free public transport, and restrictive programs such as increasing parking fees can reduce air pollution in cities. In Oslo, increases in parking fees were the most effective measurements to control the air pollution in Norway (2011) [ 34 ].

Control measures on vehicles .

The most important control measures on vehicles to control air pollution listed in Table ​ Table3, 3 , are as follows:

Emission control on in-use and new vehicles [ 36 ], tightening vehicle emission standards [ 51 , 57 – 59 , 61 , 62 , 72 , 76 , 94 ], the installation of either diesel particulate filters (DPF) or diesel oxidation catalysts (DOC) on all diesel-powered trucks, buses [ 71 ], convert delivery trucks to LP gas and install catalytic converters [ 53 ], use of catalytic converters [ 33 , 67 , 72 ], use of three-way vehicle exhaust catalytic converters (VECs) [ 97 ], retrofit in-use vehicles [ 48 – 50 ], retrofitting emission control devices [ 59 ], motorcycle (and Similar) Emission Control Program [ 90 ], retrofit carbureted LDGVs [ 37 ].

Focusing on vehicle emission restrictions is more important than on urban air quality restrictions. Therefore, stricter standards are mainly considered for new cars [ 67 ]. Standards are a series of driving cycle emission regulations enacted for control the air pollutants emitted from the light- and heavy-duty vehicles and motorcycles [ 36 ]. Although vehicle emission control strategies can be easily proposed, however, they are hard to implement due to their dependency on the public acceptance and support [ 61 ]. Euro emission standards are one of the most important measures that governments plan and implement to control vehicle emissions. In Beijing, for example, from 1999 to 2008, Euro 1 to 4 standards were planned and implemented for variety of vehicles [ 36 ]. Vehicle Exhaust Catalysts (VECs) was enacted to control or reduce the many air pollutants (NO x , VOCs and CO) emitted from the petrol-fueled vehicles. The results of study conducted by Hutchinson in the UK in 2004 reported that VECs significantly reduce the concentration of pollutants: NO 2 (20%), PM10 (10%), VOCs (30%) and CO (70%) [ 97 ]. In diesel vehicles, the traditional Diesel Catalyst Oxidation (DOC) has been employed to decrease the concentration of THC and CO. In addition, Diesel Particle Filters (DPF) and Selective Catalyst Reduction (SCR) systems have been also employed to reduce the particle and NOx emissions, respectively [ 120 , 121 ]. In a study focused on investigation the contribution of a new generation diesel light-duty vehicles (Euro 6) on the urban air quality, the results showed a 60% decrease in NO 2 emissions [ 122 ].

Fuel quality improvements and alternative fuels .

The most important measurements related to fuel quality improvements and the use of alternative fuels to control air pollution are listed in Table ​ Table3 3 :

Fuel quality improvements or raising fuel standards or updating vehicle fuel standards [ 36 , 40 , 43 , 45 , 48 – 50 , 57 – 59 , 62 , 73 , 89 , 94 ], complete removal of leaded petrol [ 67 , 72 ], diesel with low Sulfur content [ 90 ], the use of alternative fuels [ 36 , 81 , 83 , 87 , 91 , 102 ], the use of ethanol derived from sugar cane [ 90 ], switching diesel vehicles to liquefied petroleum gas (LPG) vehicles [ 59 ], increased use of alternative fuels (CNG, LNG) [ 45 , 48 – 50 ], the use of CNG as a cleaner fuel in vehicles [ 65 , 67 , 73 , 90 ], the use of electric vehicles powered by batteries or fuel cells and use of cleaner-burning fuels (such as methanol) [ 84 ], shifting the public transport buses from diesel to CNG [ 62 ], bio-fuel vehicle, Hybrid vehicle, Electric vehicle, LPG [ 73 ], buses to switch over to CNG or other clean fuel [ 67 , 72 ] promotion of biofuels [ 62 – 64 ].

Several studies have confirmed the relationship between fuel quality and air pollution [ 123 – 125 ]. One of the preconditions for adopting emission standards is to improve the fuel quality. As an example, the removal of Lead (Pb) from gasoline is the main prerequisite for accepting the Euro 1 standard [ 36 ]. Using alternative fuels instead of fossil fuels is an important step in reducing urban air pollution. Brazil uses fuels such as sugar cane-derived ethanol and compressed natural gas on a large scale as gasoline alternatives. More than 50% of the fuel used in Brazilian light vehicles is ethanol [ 90 ]. In 1999, buses running on CNG were introduced into the Beijing bus fleet [ 36 ]. Hybrid and electric vehicles are a good alternative to fossil fuel vehicles and are effective in reducing air pollution. Many of the biggest automobile producers have been producing hybrid and electric vehicles for years, and very countries like China, Korea, Philippines, Singapore, Thailand, India, Japan, Malaysia use them [ 73 , 126 ].

Traffic restrictions .

The most important measurements related to Traffic restrictions to control air pollution listed in Table ​ Table3, 3 , are as follows:

Establishing restricted area in the center of the city [ 72 ], implementation of LEZ [ 34 , 87 , 92 , 99 , 101 ], increasing the tolls that give access to the inner parts of the city [ 34 ], by-pass construction in the congested area [ 100 ], environmental optimization of traffic signal timings [ 109 ], other vehicle restrictions [ 88 ], restrictions on the use of private cars [ 47 ], restriction on entry of truck traffic [ 68 ], enforcement of odd–even scheme for private cars [ 34 , 68 ], defining priority lanes for low emission vehicles [ 34 ].

One of the control measurements that has attracted a lot of attention in many industrialized countries is LEZ. The use of vehicles is restricted in these areas, mostly in the city centers and crowded places of the city. In some cities, LEZ is considered for diesel-burning heavy-duty vehicles. However, some of these restrictions are also being applied to other types of vehicles, such as very old and polluting vehicles. In some countries such as England, Germany, and the Netherlands, vehicles are assigned a sticker (red, yellow, or green) according to the tax class and Euro emission standard. In some countries, only vehicles with certain emission standards and with the relevant label are allowed to enter to the special zone [ 95 , 127 ]. Numerous studies have been investigated to analyze the influence of LEZ on air quality. Most of them declared the LEZ to be effective in reducing the concentration of air pollutants [ 99 , 101 , 128 , 129 ]. The results of study conducted by Cesaroni in 2012 Rome reported that implementation the LEZ approach have been reduced the NO 2 and PM 10 concentrations by 23 and 10%, respectively. However, the reductions were mostly in the intervention area not the whole city [ 92 ]. Congestion charging areas are defined as areas of the city that have special rules for entering them, such as paying tolls. There is evidence that congestion charging improves the air quality via behavior changes including using public transportation instead of private car [ 130 ]. In Oslo, Norway, since 2017, in the congestion charging zones, vehicles pay different prices depending on the type of fuel, the EURO standard, type of car (heavy, light), and time of day (rush hour, not rush hour). Of course, Electric vehicles can pass free in this area [ 34 ]. The odd–even scheme for private vehicles based on license plate numbers is one of the traffic restrictions which is usually applied in the case of emergency air pollution and temporarily for some big cities in a larger geographical area than other traffic restrictions [ 34 , 68 ].

Strategies and policies related to energy

The most important measurements related to energy consumption for control air pollution listed in Table ​ Table3, 3 , are as follows:

Cleaner energy use [ 38 , 51 , 54 ], energy efficient (EE) improvement [ 44 , 48 , 106 ], energy saving [ 106 ], energy replacement [ 43 ], use of solar energy [ 84 ], clean technologies such as the fuel cell [ 85 ], utilizing the clean coal [ 48 – 51 , 56 ], coal control in electricity generation sector [ 40 ], increasing clean energy alternatives such as coal-to-gas or coal-to-electricity, elimination of civil bulk coal consumption and adjusting and optimizing the energy structure [ 48 – 50 ], the use of renewables and nuclear energy [ 62 – 64 ], cleaner cooking fuels (i. e. LPG, electricity) and cleaner cook stoves [ 62 – 64 ], wood heater replacement program [ 75 ], restriction on the use of coal by residential, and commercial sources [ 78 ], changes in the price of electricity and shifts in coal usage [ 82 ], control of domestic heating [ 91 ], tax on a single fuel, such as coal and ban on coal use [ 105 ], banning the marketing, sale, and distribution of bituminous coal [ 107 , 108 ], signing the natural gas agreement with the former USSR and banning the use of poor quality lignite [ 103 ], restriction on use of coal/wood-based tandoor in restaurants and street eateries [ 68 ], taxes on wood consumption for heating and cooking and subsidies for more efficient combustion technologies [ 112 ], a 70% subsidy for the cost of coal heater replacement with a clean-burning, solid fuel replacement, using only a certain type of fuel and formation of foundation [ 27 ].

Energy is an integral part of human life. Energy sources have a lot of changes due to the advancement of science and technology. Coal is one of the energy sources used for many years in both industry and home heating. The residential coal-burning was known as the most probable source of pollutants for the London Smog. This disaster caused 4000 excess deaths in one week in the London area in1952 [ 27 ]. Two of the most important actions in the UK government after this catastrophe were approval of the Clean Air Act in 1956 and allocating 70% subsidies to replace coal fuel heaters with clean fuel heaters. The contribution of the federal government for controlling the air pollution was calculated to be 40%, while the contribution of local government were the remaining 30% [ 131 ]. Other countries also take good measures to remove coal, especially from home use. The Turkish government signed a natural gas agreement with the former USSR in 1984. Distribution of the natural gas started in Istanbul in January 1992 and the use of poor-quality lignite was banned in late 1993 [ 103 ]. Wood stoves became increasingly the popular for home heating in Tasmania, Australia in the late 1980s and early 1990s. In this regard, some studies were conducted from 1991 to 1993, and results indicated that the main source of air pollution was solid fuel. The government improved air quality by allocating funds to replace electricity instead of solid fuel [ 75 ]. In 2013, it was reported that coal in China is still the main source of energy, unlike other developed countries in the world. Approximately 52% of coal in China is consumed in the electricity generation sector [ 53 ]. The results of a study in Dublin, Ireland reported that after banning coal sales, the average black smoke concentrations, adjusted non-trauma death rates, respiratory deaths and cardiovascular deaths declined by 70%, 5.7%, 5.15%, 10.3%, respectively [ 107 ]. Clean technical advances (CTP), energy efficient (EE) improvement, and energy savings, in addition to socioeconomic impacts, can reduce emissions of SO 2 , CO 2 , and PM 2.5 [ 44 ].

Strategies and policies related to the industry

The most important measurements related to the industry for control air pollution listed in Table ​ Table3, 3 , are as follows:

Industrial structure improvement [ 38 , 48 – 50 , 54 , 91 ], adjustment of industrial structure [ 48 – 50 ], installation of control equipment on industrial and commercial boilers [ 33 ], required use of abatement equipment [ 76 , 77 ], measures in connection with the licensing procedures for industrial plants [ 93 ], the substantial elevation of emissions fees and fines [ 104 ], the (re)location of industrial facilities [ 47 , 87 ], elimination or upgrading industries with excessive, backward, and polluting industries, reduce volatile organic compounds (VOCs) emission, promote cleaner production (CP) and accelerate the technological transformation and improve innovation capability [ 48 – 50 ], tightening exhaust emission standards for industry [ 57 ], use of higher chimney [ 27 , 91 ], stopping some factories in a pollution emergency [ 48 – 50 , 87 ], use of high efficiency electrostatic precipitator technology in large coal-based power plants and emission regulations for industries [ 62 – 64 ].

The presence of industries near the cities and the emission of various pollutants have made governments to enact strict laws and policies in order to control air pollution caused by industries. Due to the antiquity of some industries and the advancement of scientific knowledge, improving the industrial structure is considered the most important and effective measurement for reduction the urban air pollution [ 38 , 48 – 50 , 91 ]. Implementation the industrial structure improvement and regulation policies in Jinan and China, reduced SO 2 and NO 2 emissions by 37.51% and 7.47%, respectively [ 49 ]. Licensing procedures for industrial plants, the substantial elevation of pollutants emission fines, and stopping some factories in a pollution emergency are other useful measures to significantly reduce air pollution [ 48 – 50 , 87 , 93 , 104 ]. Of course, every industry should have control measures according to the type of environmental pollutants [ 48 ], which is not discussed in this article.

The urban air pollution control strategies and policies with focus on six categories based on the types of pollutants such as PM, SO 2 , NO 2 , VOC S , O 3 , and photochemical smog are listed in Table ​ Table4 4 .

The most important measures to PM control

Reduction the nitrogen oxides (NO x ) and sulfur dioxide (SO 2 ) [ 132 ], fuel quality improvements [ 133 , 140 ], school and governmental sector closure, shutdowns of construction works, and traffic limitation (at the time of air pollution) [ 133 ], low emission zones (LEZ) [ 134 , 141 ], traffic management and improved public transport [ 134 , 137 ], control of open biomass burning and fossil- fuel combustion [ 135 ], electrifying public transportation, upgrading coal-fired power plants [ 115 ], eliminating small coal-fired boilers, phasing out small high-emitting factories [ 136 ], the odd–even car scheme [ 138 ], coal consumption reduction, energy structure reconstruction tighter emission rules, improvement of the industrial and motor vehicle waste control techniques [ 139 ], industrial source controls, targeted mobile source controls, street sweeping, road paving, general mobile source controls, general fugitive control strategies [ 140 ], restrict speed, treat unpaved access roads, required use of abatement equipment in industry [ 143 ], reduce emissions from old, diesel vehicles, increase the use of eco-friendly vehicles including electric cars and hydrogen cars [ 142 ].

A variety of air pollutant, in particular, PM adversely affect the quality of Urban air. Among major contaminants, fine particulates due to adverse health effects has drawn much attention [ 163 , 164 ]. In the case of air pollution, governments often use both short-term and long-term strategies. For example in Iran, government have made such effort to control the via implementing the temporary urgent control strategies including as shutdowns of construction works and traffic restrictions and school and governmental sector closure, [ 133 ]. Control measures in transportation can reduce concentration of particulate matter. The results of a study on the low emission zones in Germany showed that after implementation of LEZ in Cologne, Berlin, and Munich in a short time, the PM 10 concentration considerably decreased. A significant reduction in PM 2.5 related to traffic-related particle fraction was observed in Munich [ 141 ]. Implementation of the odd–even car trial scheme in India in 2016 showed that the average hourly rates of PM 2.5 and PM 10 decreased by 74% compared to the corresponding hours during the previous year [ 138 ]. The results of a study conducted in eastern China indicated that the most important factors influencing PM 2.5 concentration are controlling the open biomass burning and fossil-fuel combustion [ 135 ]. Depending on the origin of the particulate matter, controlling other pollutants can also reduce its concentration. For instance, research on air pollution control measures in Los Angeles showed that controls of SO x applied to the base emissions inventory decreased the average PM 2.5 concentrations by 1.2 µg m −3 . The ammonia control measures reduced daily PM 2.5 concentrations by 10.9 µg m −3 in comparison with its base concentrations [ 143 ].

The most important measures to SO 2 control

Regional Clean Air Incentives Market, electric vehicles [ 143 ] reducing the sulfur content of the fuel [ 143 , 145 , 147 ], fuel desulfurization, substitution with low-sulfur alternatives, industrial structural change, production process efficiency [ 144 ], promoting efficient energy use [ 145 – 147 ], sulfur tax [ 146 ], closing small and high-emitting power plants [ 147 ], installing flue-gas desulfurization (FGD) equipment in all the power plants [ 147 , 148 ], burning low sulfur western coal [ 148 ], fuel switching, load shifting, environmental dispatch or intermittent controls [ 149 ]. Most of the control measures for reducing the SO 2 emission are related to the improvement and modification of the energy efficiency. Changing the energy structure with a significant reduction in coal consumption and the use of alternative fuels such as natural gas and electricity has been the most important measure to reduce SO 2 emissions [ 48 ]. Increasing energy efficiency from 2005 to 2008 and measures such as closing small and high-emitting power plants, installation of flue gas desulfurization (FGD) equipment in all power plants, emission control from boilers and kilns, promotion of cleaner production, and using fuel with lower sulfur contents in the Pearl River Delta (PRD) region of China reduced SO 2 concentration by 39% between 2006 and 2009 [ 147 ]. Improving and changing the vehicle fuel and the use of electric vehicles are other important measures to reduce SO 2 emissions [ 143 ].

The most important measures to NO 2 control

Vehicle emission standards, inspection and maintenance (I/M) program, scrappaging and old vehicle retrofitting practices, gasoline quality improvement, controlling non-road engines, alternative-fuel vehicles [ 150 ], the natural gas vehicle supply (NGVS) program, use of diesel particulate filter (DPF) or diesel oxidation catalyst (DOC), cash incentives or tax reductions for the vehicles of low pollutant emissions and hybrid fuel [ 151 ]. Electrify stationary no generating internal combustion engines and turbines, eliminate planned fires, selective catalytic reduction in petroleum refinery, radiant burners; alternative fuels in small boilers and process heaters [ 143 ].

Vehicles (especially privatized cars and motorcycles) contribute between 30 and 75% of the total NO x emissions in cities, therefore, most measures to reduce NO 2 emissions in urban areas are related to transportation [ 165 – 167 ]. A study focused on NO 2 trend in the long-term period alongside 16 urban roadside locations in 7 major Korean cities over 11-year period (1998–2008). The use of low emission diesel engines and natural gas-burning vehicles program were considered as key emission control strategies since June 2000. The results showed that NO 2 levels decreased over 11 years due to the combined effects of control strategies [ 151 ]. Energy-related control measures comprise the use of natural gas for conservation of commercial and residential energy. Important measures taken in the industry to reduce NO 2 emissions include the use of selective catalytic converters, the elimination of radiant burners, the improvement of combustion, and the use of alternative fuels instead of highly polluting fossil fuels [ 143 ].

The most important measures to VOCS control

Change from diesel to liquefied petroleum gas (LPG), use of catalytic converter replacement [ 152 ], reduce the use of solvents, reduce the VOCs of vehicle exhaust [ 153 ].

The most important sources of VOCs emission are biological resources, vehicles, and industries. After industrial revolution in the eighteenth century, the spread of VOCs gradually increased in cities. [ 168 ]. In the light of industrial revolution and controlling measurement for VOCs, most public light buses and taxies in Hong Kong were modified from the diesel-burning buses to liquefied petroleum gas (LPG) fuel type in the early 2000s. The government carried out an LPG catalytic converter replacement program (CCRP) from October 2013 to April 2014 which reduced VOCs by 36.7% [ 152 ]. Reducing solvent use and vehicle exhaust VOCs have been implemented in the Korean metropolis of Seoul since 2005 as appropriate strategies for reducing VOCs [ 153 ]. While the local reduction of nitrous oxides was the main controlling strategy for ozone in the Macon, Georgia in 2004 [ 158 ].

The most important measures to O 3 control

Progressive and more stringent controls on emissions of oxides of nitrogen (NO x ) and volatile organic compounds (VOCs) [ 154 ], ozone control of four source categories including electric utility point sources, nonutility (industrial) point sources, highway vehicles, and non-road mobile sources [ 155 ], vapor control in gasoline marketing [ 156 ], cleaner emission standards on newer cars according to the Clean Air Act [ 157 ], achieve ozone standards [ 158 ], restricting heavy-duty diesel trucks from driving within urban areas during the daytime in major cities [ 159 ], reduction of both NO x and VOC anthropogenic emissions, circulation on alternate days of vehicles with odd and even number plates, traffic restrictions on some roads, closure of industries, reduction in the operation regime of some industries [ 160 ].

Ozone in the Earth's atmosphere is produced by the photochemical reactions of NO x and VOCs in the presence of sunlight. The relationship between ozone formation and concentration of its precursors is nonlinear [ 169 – 171 ]. The rate of ozone formation depends on the NO x concentration and the VOC/NO x ratio [ 154 ]. To achieve the national standard for ambient air quality for ozone, the US government implemented different preventive measurements: uses of low solvent technologies and/or add-on control equipment for surface coating operations, vapor control in gasoline marketing, maintenance programs for proper VOCs control as the procedures for ozone, and vehicle inspection [ 156 ]. Implementation the strict limitation for driving the heavy-duty diesel trucks in urban areas during the daytime in several major Chinese cities in 2006 reduced ozone by about 25 and 20 ppb at night and day, respectively [ 159 ].

The most important measures to photochemical smog control

Ambient air standards, emission standards, and applying appropriate control techniques [ 162 ].

Photochemical smog was first detected in Los Angeles. The main influencing factor for this phenomenon was emission of air pollutants from different plants (power plants, smelters, foundries, open dumps, incinerators), and the release of sulfur oxides from different refineries. Adoption of emission standards regarding the control of vehicles and industry was one of the most important measures taken by the government to solve the problem of photochemical smog [ 162 ].

Conclusions

A systematic review was conducted to identify policies and strategies to control urban air pollution without restrictions in countries and time. In this study, the selected articles were divided into two categories: (1) that introduce policies and strategies to control air pollution in different countries of the world, and (2) articles that introduce different policies and strategies to control one or more specific pollutants. In the first category, urban air pollution control strategies and policies were classified into four categories, namely focusing on general strategies and policies, transportation, energy and Industry. In the second category, policies and strategies focused on controlling six pollutants (PM, SO 2 , NO 2 , VOCS, Ozone and photochemical smog).

Legislations and policy interventions to control urban air pollution are commonly enacted and implemented in most of the large countries in the world. Policies used by governments to control air pollution can be encouraging, supportive, or punitive. Depending on the circumstances, these policies are implemented alone or jointly.

The largest share of air pollution, especially in large cities, is related to transportation [ 172 ]. According to our investigations, the number of articles covering transportation control strategies and policies is higher than other topics. Important policies and strategies related to transportation include the use of technology to improve vehicle efficiency, improve transportation structure, use of emission standards, fuel quality improvements and alternative fuels, traffic restrictions, and use of less polluting vehicles such as hybrid vehicles and electric. Preliminary studies on energy-related air pollution control policies and strategies have focused on eliminating solid fuels, especially coal, and shifting fuel from coal to cleaner energy sources such as electricity and natural gas. This fuel shift has taken place in many countries for domestic use. But some governments in recent years have defined policies and strategies to remove coal from industry, especially power plants, which show that coal is still an important fuel in those countries. In recent years the approach of some countries is to use cleaner energies such as solar and wind energies. Installation of air pollution control systems, use of clean energy, use of up-to-date technologies in production, and, if necessary, the relocation of industrial facilities are the most important measures to control urban air pollution related to the industry.

This study may enhance knowledge about air pollution control interventions. We provided a complete set of implemented policies and strategies by governments to reduce air pollution or improve air quality in various fields to be used by planners and decision makers in this area.

Acknowledgements

The authors thank the Research Center for Environmental Health Technology, Iran University of Medical Sciences for the provision of financial support [Grant No.99-3-61-19814]. (Ethics Code: IR.IUMS.REC.1399.1364).

Declarations

The authors formally declare no conflict(s) of interest.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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5 effective methods to control air pollution (explained with diagram).

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Some of the effective methods to Control Air Pollution are as follows: (a) Source Correction Methods (b) Pollution Control equipment (c) Diffusion of pollutant in air (d) Vegetation (e) Zoning.

(a) Source Correction Methods :

Industries make a major contribution towards causing air pollution. Formation of pollutants can be prevented and their emission can be minimised at the source itself.

By carefully investigating the early stages of design and development in industrial processes e.g., those methods which have minimum air pollution po­tential can be selected to accomplish air-pollution control at source itself.

These source correction methods are:

(i) Substitution of raw materials :

If the use of a particular raw material results in air pollution, then it should be substituted by another purer grade raw material which reduces the formation of pollutants. Thus,

(a) Low sulphur fuel which has less pollution potential can be used as an alter­native to high Sulphur fuels, and,

(b) Comparatively more refined liquid petroleum gas (LPG) or liquefied natu­ral gas (LNG) can be used instead of traditional high contaminant fuels such as coal.

(ii) Process Modification :

The existing process may be changed by using modified techniques to control emission at source. For example,

(a) If coal is washed before pulverization, then fly-ash emissions are consider­ably reduced.

(b) If air intake of boiler furnace is adjusted, then excess Fly-ash emissions at power plants can be reduced.

(iii) Modification of Existing Equipment :

Air pollution can be considerably minimised by making suitable modifications in the existing equipment:

(a) For example, smoke, carbon-monoxide and fumes can be reduced if open hearth furnaces are replaced with controlled basic oxygen furnaces or elec­tric furnaces.

(b) In petroleum refineries, loss of hydrocarbon vapours from storage tanks due to evaporation, temperature changes or displacement during filling etc. can be reduced by designing the storage tanks with floating roof covers.

(c) Pressurising the storage tanks in the above case can also give similar re­sults.

(iv) Maintenance of Equipment :

An appreciable amount of pollution is caused due to poor maintenance of the equipment which includes the leakage around ducts, pipes, valves and pumps etc. Emission of pollutants due to negligence can be minimised by a routine checkup of the seals and gaskets.

(b) Pollution Control Equipment :

Sometimes pollution control at source is not possible by preventing the emis­sion of pollutants. Then it becomes necessary to install pollution control equip­ment to remove the gaseous pollutants from the main gas stream.

The pollutants are present in high concentration at the source and as their distance from the source increases they become diluted by diffusing with envi­ronmental air.

Pollution control equipment’s are generally classified into two types:

(a) Control devices for particulate contaminants.

(b) Control devices for gaseous contaminants.

In the present book only the control devices for particulate contaminants are dealt with.

Control Devices for Particulate Contaminants:

(1) Gravitational Settling Chamber :

For removal of particles exceeding 50 µm in size from polluted gas streams, gravitational settling chambers (Fig 5.1) are put to use.

This device consists of huge rectangular chambers. The gas stream polluted with particulates is allowed to enter from one end. The horizontal velocity of the gas stream is kept low (less than 0.3 m/s) in order to give sufficient time for the particles to settle by gravity.

The particulates having higher density obey Stoke’s law and settle at the bot­tom of the chamber from where they are removed ultimately. The several hori­zontal shelves or trays improve the collection efficiency by shortening the settling path of the particles.

(2) Cyclone Separators (Reverse flow Cyclone):

Instead of gravitational force, centrifugal force is utilized by cyclone separators, to separate the particulate matter from the polluted gas. Centrifugal force, several times greater than gravitational force, can be generated by a spinning gas stream and this qual­ity makes cyclone separators more effec­tive in removing much smaller parti­culates than can possibly be removed by gravitational settling chambers.

A simple cyclone separator (Fig 5.2) con­sists of a cylinder with a conical base. A tangential inlet discharging near the top and an outlet for discharging the particulates is present at the base of the cone.

Mechanism of Action:

The dust laden gas enters tangentially, receives a rotating motion and generates a centrifugal force due to which the particulates are thrown to the cyclone walls as the gas spirals upwards inside the cone (i.e. flow reverses to form an inner vortex which leaves flow through the outlet). The particulates slide down the .walls of the cone and are discharged from the outlet.

(3) Fabric Filters (Baghouse Filters):

In a fabric filter system, a stream of the polluted gas is made to pass through a fabric that filters out the particulate pollutant and allows the clear gas to pass through. The particulate matter is left in the form of a thin dust mat on the insides of the bag. This dust mat acts as a filtering medium for further removal of particulates increasing the efficiency of the filter bag to sieve more sub mi­cron particles (0.5 µm).

A typical filter (Fig 5.3) is a tubular bag which is closed at the upper end and has a hopper attached at the lower end to collect the particles when they are dislodged from the fabric. Many such bags are hung in a baghouse. For efficient filtration and a longer life the filter bags must be cleaned occasionally by a mechanical shaker to prevent too many particulate layers from building up on the inside surfaces of the bag.

(4) Electrostatic Precipitators:

The electrostatic precipitator (Fig. 5.4) works on the principle of electrostatic precipitation i.e. electrically charged particulates present in the polluted gas are separated from the gas stream under the influence of the electrical field.

A typical wire and pipe precipitator consists of:

(a) A positively charged collecting surface (grounded).

(b) A high voltage (50 KV) discharge electrode wire.

(c) Insulator to suspend the electrode wire from the top.

(d) A weight at the bottom of the electrode wire to keep the wire in position.

The polluted gas enters from the bottom, flows upwards (i.e. between the high voltage wire and grounded collecting surface). The high voltage in the wire ionises the gas. The negative ions migrate towards the grounded surface and pass on their negative charge to the dust particles also. Then these negatively charged dust particles are electrostatically drawn towards the positively charged collector surface, where they finally get deposited.

The collecting surface is rapped or vibrated to periodically remove the collected dust-particles so that the thickness of the dust layer deposited does not exceed 6 mm, otherwise the electrical attraction becomes weak and efficiency of the electrostatic precipitator gets reduced.

As the electrostatic precipitation has 99 + percent efficiency and can be oper­ated at high temperatures (600°C) and pressure at less power requirement, therefore, it is economical and simple to operate compared to other devices.

(5) Wet Collectors (Scrubbers):

In wet collectors or scrubbers, the particulate contaminants are removed from the polluted gas stream by incorporating the particulates into liquid droplets.

Common wet scrubbers are:

(i) Spray Tower

(ii) Venturi Scrubber

(iii) Cyclone Scrubber

(i) Spray Tower:

Water is introduced into a spray tower (Fig. 5.5.) by means of a spray nozzle (i.e. there is downward flow of water). As the polluted gas flows upwards, the particulates (size exceeding 10 µm) present collide with the water droplets be­ing sprayed downward from the spray nozzles. Under the influence of gravita­tional force, the liquid droplets containing the particulates settle to the bottom of the spray tower.

(ii) Venturi Scrubber:

Submicron particulates (size 0.5 to 5 µn) associated with smoke and fumes are very effectively removed by the highly efficient Venturi Scrubbers. As shown in Fig 5.6 a Venturi Scrubber has a Venturi shaped throat section. The polluted gas passes downwards through the throat at the velocity of 60 to 180 m/sec.

A coarse water stream is injected upwards into the throat where it gets atomised (i.e. breaks the water into droplets) due to the impact of high velocity of the gas. The liquid droplets collide with the particulates in the pol­luted gas stream.

The particles get entrained in the droplets and fall down to be removed later on. Venturi Scrubbers can also remove soluble gaseous contami­nants. Due to the atomisation of water there is proper contact between the liquid and the gas increasing the efficiency of the Venturi Scrubber (their power cost is high because of the high inlet gas velocity).

To separate the droplets carrying the particulate matter from the gas stream, this gas-liquid mixture in the Venturi Scrubber is then directed into a separa­tion device such as a cyclone separator.

(iii) Cyclone Scrubber:

The dry cyclone chamber can be converted into a wet cyclone scrubber by in­serting high pressure spray nozzles at various places within the dry chamber (Fig. 5.7).

The high pressure spray nozzles generate a fine spray that intercepts the small particles in the polluted gas. The centrifugal force throws these particles to­wards the wall from where they are drained downwards to the bottom of the scrubber.

(c) Diffusion of Pollutants in Air:

Dilution of the contaminants in the atmosphere is another approach to the con­trol of air pollution. If the pollution source releases only a small quantity of the contaminants then pollution is not noticeable as these pollutants easily diffuse into the atmos­phere but if the quantity of air contaminants is beyond the limited capacity of the environment to absorb the contaminants then pollution is caused.

However, dilution of the contaminants in the atmosphere can be accomplished through the use of tall stacks which penetrate the upper atmospheric layers and disperse the contaminants so that the ground level pollution is greatly re­duced. The height of the stacks is usually kept 2 to 2 1 / 2 times the height of nearby structures.

Dilution of pollutants in air depend on atmospheric temperature, speed and direction of the wind. The disadvantage of the method is that it is a short term contact measure which in reality brings about highly undesirable long range effects.

This is so because dilution only dilutes the contaminants to levels at which their harmful effects are less noticeable near their original source whereas at a considerable distance from the source these very contaminants eventually come down in some form or another.

(d) Vegetation:

Plants contribute towards controlling air-pollution by utilizing carbon dioxide and releasing oxygen in the process of photosynthesis. This purifies the air (re­moval of gaseous pollutant—CO 2 ) for the respiration of men and animals.

Gas­eous pollutants like carbon monoxide are fixed by some plants, namely, Coleus Blumeri, Ficus variegata and Phascolus Vulgaris. Species of Pinus, Quercus, Pyrus, Juniperus and Vitis depollute the air by metabolising nitrogen oxides. Plenty of trees should be planted especially around those areas which are de­clared as high-risk areas of pollution.

(e) Zoning:

This method of controlling air pollution can be adopted at the planning stages of the city. Zoning advocates setting aside of separate areas for industries so that they are far removed from the residential areas. The heavy industries should not be located too close to each other.

New industries, as far as possible, should be established away from larger cities (this will also keep a check on increasing concentration of urban population in a few larger cities only) and the locational decisions of large industries should be guided by regional planning. The industrial estate of Bangalore is divided into three zones namely light, medium and large industries. In Bangalore and Delhi very large industries are not permitted.

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• Biology Article

Air Pollution Control

Air pollution & its control, air pollution definition.

“Air Pollution is the release of pollutants such as gases, particles, biological molecules, etc. into the air that is harmful to human health and the environment.”

Air Pollution Diagram

Table of Contents

What is Air Pollution?

Types of air pollutants, primary pollutants, secondary pollutants, causes of air pollution.

Air pollution refers to any physical, chemical or biological change in the air. It is the contamination of air by harmful gases, dust and smoke which affects plants, animals and humans drastically.

There is a certain percentage of gases present in the atmosphere. An increase or decrease in the composition of these gases is harmful to survival. This imbalance in the gaseous composition has resulted in an increase in earth’s temperature, which is known as global warming.

There are two types of air pollutants:

The pollutants that directly cause air pollution are known as primary pollutants. Sulphur-dioxide emitted from factories is a primary pollutant.

The pollutants formed by the intermingling and reaction of primary pollutants are known as secondary pollutants. Smog, formed by the intermingling of smoke and fog, is a secondary pollutant.

Also Read:  Water Pollution

Following are the important causes of air pollution:

Burning of Fossil Fuels

The combustion of fossil fuels emits a large amount of sulphur dioxide. Carbon monoxide released by incomplete combustion of fossil fuels also results in air pollution.

Automobiles

The gases emitted from vehicles such as jeeps, trucks, cars, buses, etc. pollute the environment. These are the major sources of greenhouse gases and also result in diseases among individuals.

Agricultural Activities

Ammonia is one of the most hazardous gases emitted during agricultural activities. The insecticides, pesticides and fertilisers emit harmful chemicals in the atmosphere and contaminate it.

Factories and Industries

Factories and industries are the main source of carbon monoxide, organic compounds, hydrocarbons and chemicals. These are released into the air, degrading its quality.

Mining Activities

In the mining process, the minerals below the earth are extracted using large pieces of equipment. The dust and chemicals released during the process not only pollute the air, but also deteriorate the health of the workers and people living in the nearby areas.

Domestic Sources

The household cleaning products and paints contain toxic chemicals that are released in the air. The smell from the newly painted walls is the smell of the chemicals present in the paints. It not only pollutes the air but also affects breathing.

Effects of Air Pollution

The hazardous effects of air pollution on the environment include:

Air pollution has resulted in several respiratory disorders and heart diseases among humans. The cases of lung cancer have increased in the last few decades. Children living near polluted areas are more prone to pneumonia and asthma. Many people die every year due to the direct or indirect effects of air pollution.

Global Warming

Due to the emission of greenhouse gases, there is an imbalance in the gaseous composition of the air. This has led to an increase in the temperature of the earth. This increase in earth’s temperature is known as global warming . This has resulted in the melting of glaciers and an increase in sea levels. Many areas are submerged underwater.

The burning of fossil fuels releases harmful gases such as nitrogen oxides and sulphur oxides in the air. The water droplets combine with these pollutants, become acidic and fall as acid rain which damages human, animal and plant life.

Ozone Layer Depletion

The release of chlorofluorocarbons, halons, and hydrochlorofluorocarbons in the atmosphere is the major cause of depletion of the ozone layer. The depleting ozone layer does not prevent the harmful ultraviolet rays coming from the sun and causes skin diseases and eye problems among individuals. Also Read:  Ozone Layer Depletion

Effect on Animals

The air pollutants suspend in the water bodies and affect aquatic life. Pollution also compels the animals to leave their habitat and shift to a new place. This renders them stray and has also led to the extinction of a large number of animal species.

Following are the measures one should adopt, to control air pollution:

Avoid Using Vehicles

People should avoid using vehicles for shorter distances. Rather, they should prefer public modes of transport to travel from one place to another. This not only prevents pollution, but also conserves energy.

Energy Conservation

A large number of fossil fuels are burnt to generate electricity. Therefore, do not forget to switch off the electrical appliances when not in use. Thus, you can save the environment at the individual level. Use of energy-efficient devices such as CFLs also controls pollution to a greater level.

Use of Clean Energy Resources

The use of solar, wind and geothermal energies reduce air pollution at a larger level. Various countries, including India, have implemented the use of these resources as a step towards a cleaner environment.

Other air pollution control measures include:

• By minimising and reducing the use of fire and fire products.
• Since industrial emissions are one of the major causes of air pollution, the pollutants can be controlled or treated at the source itself to reduce its effects. For example, if the reactions of a certain raw material yield a pollutant, then the raw materials can be substituted with other less polluting materials.
• Fuel substitution is another way of controlling air pollution. In many parts of India, petrol and diesel are being replaced by CNG – Compressed Natural Gas fueled vehicles. These are mostly adopted by vehicles that aren’t fully operating with ideal emission engines.
• Although there are many practices in India, which focus on repairing the quality of air, most of them are either forgotten or not being enforced properly. There are still a lot of vehicles on roads which haven’t been tested for vehicle emissions.
• Another way of controlling air pollution caused by industries is to modify and maintain existing pieces of equipment so that the emission of pollutants is minimised.
• Sometimes controlling pollutants at the source is not possible. In that case, we can have process control equipment to control the pollution.
• A very effective way of controlling air pollution is by diluting the air pollutants.
• The last and the best way of reducing the ill effects of air pollution is tree plantation. Plants and trees reduce a large number of pollutants in the air. Ideally, planting trees in areas of high pollution levels will be extremely effective.

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Air Pollution Control

Introduction.

Every day, we take 23,000 breaths. I'm at home. I'm at work. You're in your automobile. On your way to work. That's quite a few breaths.

Breathing is something that most of us don't think about because it isn't something we can see. It's difficult to tell what's in the air around you when you can't see pollutants like invisible gases or particles.

Most people are unaware that according to the World Health Organization, more than 90% of the world's population breathes polluted air. Everyone is affected by this frightening figure, notably youngsters, the elderly, and asthmatics.

If you take a look at the causes of air pollution, you will realize that humans are primarily responsible for air pollution. The growing industrialization has positive and negative impacts on mankind and the environment . Also, the increasing rate of environmental pollution is one of the significant drawbacks that we are facing, resulting from our deeds. Before talking about the control of air pollution, we will have to understand their meaning.

Air Pollution Definition

Air pollution means contamination of air, water, or soil by any substance that is harmful to live organisms. It’s like an introduction or release of a toxic substance into the environment, that can harm the elements in the environment. The pollution can take place because of natural (such as volcanic eruption), and man-made reasons. But nowadays, it’s man-made reasons that are causing more pollution than natural ones. From the increasing number of vehicles to ever-growing industrial wastages in the form of air or water, each contributes to air pollution in some way.

What is Air Pollution?

The air pollution definition says that when any physical, chemical, or biological change takes place in the air and contaminates it, then it is called air pollution. The contamination of air can be caused due to many factors such as poisonous or harmful gases, smoke, fog, smog, dust, etc. air pollution affects both plants as well as animals.

(Image will be uploaded soon)

Types of Air Pollutants

The air pollutants are divided into primary and secondary pollutants. Pollutants are those substances that cause air pollution.

Primary Pollutants:

The primary pollutants responsible for air pollution are the ones that directly cause air pollution. These include harmful gases such as sulfur dioxide coming from the factories. Primary pollutants are those that are produced as a direct result of the process. Sulfur dioxide, generated by factories, is a classic example of a primary pollutant.

Secondary Pollutants:

The secondary pollutants are formed by the process of intermixing or intermingling of primary pollutants. Smog, which is a combination of fog and smoke, is a secondary pollutant.

Causes of Air Pollution:

To prevent the pollution of air around, you have to understand the causes of air pollution at first. The main causes are – 

Burning of Fossil Fuels:

Fossil fuel emits harmful gases such as sulfur dioxide and carbon monoxide into the air. One of the biggest causes of air pollution is sulfur dioxide, which is emitted through the combustion of fossil fuels such as coal, petroleum for energy in power plants, and other industry combustibles.

Automobiles: 

The emission of harmful gases is caused by the excessive use of automobiles.

Agricultural Activities: 

Various processes take place during agricultural activities such as the emission of ammonia, overuse of insecticides, pesticides, and fertilizers . Ammonia is a typical byproduct of agriculture and one of the most dangerous gases in the atmosphere. Insecticides, pesticides, and fertilizers have all become increasingly common in agricultural practices. They release hazardous chemicals into the atmosphere and can pollute water.

Farmers also set fire to the fields and old crops to clear them up for the new cycle of sowing. According to reports, burning to clean up fields pollutes the air by emitting toxic pollutants. 

Factories and Industries:

Emission of harmful gases and chemicals into the air by the increasing industrial activities. Manufacturing companies emit a significant amount of carbon monoxide, hydrocarbons, organic compounds, and chemicals into the air, lowering air quality.

Manufacturing industries may be found in every corner of the globe, and no region has escaped their influence. Petroleum refineries also emit hydrocarbons and a variety of other pollutants, which damage the air and soil.

Mining Activities:

Increasing emission of harmful substances through mining activities.  Mining is the extraction of minerals from under the earth's surface utilizing heavy machinery. Dust and chemicals are released into the air throughout the process, resulting in significant air pollution.

This is one of the factors contributing to the deteriorating health of workers and inhabitants in the area.

Domestic Resources:

Effects of domestic sources such as the use of chemical paints and overuse of air conditioners. Household cleaning products and painting supplies release hazardous chemicals into the air, polluting the environment. Have you ever observed that when you paint your house's walls, it emits a noxious odor that makes it nearly impossible to breathe?

Another source of pollution is suspended particle matter, sometimes known as SPM. SPM refers to the particles that float in the air and is typically caused by dust, combustion, and other factors.

Diseases caused by air pollution:

Air Pollution can lead to increasing diseases like throat infections and lung cancer in humans. Every year, diseases related to air pollution kill and hospitalize millions of people. According to World Health Organization estimates, one out of every eight fatalities worldwide is caused by conditions related to air pollution. New research has found significant correlations between the development of respiratory and cardiovascular disorders and both outdoor and indoor air pollution. Ischemic heart disease, stroke, chronic obstructive pulmonary disease (COPD), lung cancer, and acute lower respiratory infections in children are among the most prevalent diseases induced by air pollution.

"Ischemic heart disease, or coronary heart disease," adds Kevin Wood, Vice President Sales & Marketing at Camfil USA, "is connected to the deposition of calcium or other materials like fat within the coronary artery." "This causes blockages, preventing blood from reaching the heart and other vital organs." According to new research, air pollution hastens the occlusion of arteries, increasing the risk of ischemic heart disease."

Effects of Air Pollution:

The air pollution information shows that increasing air pollution can have an adverse effect on plants, animals, and humans.

Global warming

Air Pollution can increase the amount of global warming as the temperature of the earth will keep rising with the emission of harmful gases. With rising global temperatures, rising sea levels, melting ice from colder places and icebergs, relocation, and habitat loss, an imminent crisis has already been signaled if preservation and normalization measures are not done soon.

Acid rain 

When water droplets combine with harmful chemicals and pollutants, it will lead to acid rain. When fossil fuels are burned, harmful chemicals such as nitrogen oxides and sulfur oxides are emitted into the environment. When it rains, the water droplets interact with the contaminants in the air, becoming acidic and falling to the earth as acid rain. Acid rain has the potential to harm humans, animals, and agriculture.

Ozone layer Depletion

All this will eventually lead to depletion of the ozone layer that protects us from harmful UV sun rays. The presence of chlorofluorocarbons and hydrochlorofluorocarbons in the atmosphere is degrading the ozone layer on Earth.

As the ozone layer thins, damaging rays are emitted back to Earth, potentially causing skin and eye problems. UV rays have the power to harm crops as well.

Thus, we have to work on the prevention of air pollution.

Effects on Animals

Increasing air pollution affects animals and aquatic life, leading them to stray and wander for food. Many of the animals are on the verge of extinction because of this. Animals, sometimes known as wildlife, are particularly vulnerable to the effects of air pollution. Acid rain, heavy metals, persistent organic pollutants (POPs), and other harmful compounds are all pollution concerns.

Insects, worms, clams, fish, birds, and mammals all have diverse ways of interacting with their surroundings. As a result, each animal's exposure to and vulnerability to the effects of air pollution is unique.

Air pollution has two major effects on wildlife.

It has an impact on the area or habitat in which they reside, as well as the food supply's availability and quality.

It is not easy to control air pollution, but it will require some simple steps like:

Avoid Using Vehicles

Prefer using public transport as it will reduce the emission of CO into the air. The availability of carpools can help in the reduction of vehicles which in turn reduces pollution. Prefer walking or cycling to nearby places and many such.

Energy Conservation

Use energy-efficient electrical devices at the workplace and home place. You can keep your lights switched off when not in use. The electrical appliances should be checked on a regular notice period so that it won’t affect the conservation.

Use of Clean Energy Resources

It will help to reduce the pollution level. Instead of using fossil fuels, we can use natural resources to produce energy like Solar Energy, Wind Energy, etc.

By decreasing and eliminating the usage of fire and fire-related items.

Because industrial emissions are one of the leading causes of air pollution, the pollutants can be reduced by controlling or treating them at the source. If a given raw material's reactions produce a pollutant, for example, the raw materials can be replaced with less harmful materials.

Another method of reducing pollution is to use different fuels. CNG – Compressed Natural Gas–powered vehicles are replacing petrol and diesel vehicles in many parts of India. Vehicles that aren't fully equipped with optimal emission engines are the most likely to use these.

Although India has a number of practices aimed at improving air quality, most of them have been forgotten or are not well implemented. There are still many automobiles on the road that haven't had their emissions tested.

FAQs on Air Pollution Control

1. What are the Types of Air Pollution?

There are 4 major harmful types of air pollution – carbon monoxide, sulfur dioxide, nitrogen oxides, and particulate matters and lead pollution

2. How Can the Use of Air Conditioners Cause Air Pollution?

The air conditioners release a gas called CFC (chlorofluorocarbon) which increases air pollution and adversely affects the ozone layer as well.

3. How Many People Can Die from Air Pollution?

According to the statistics provided by WHO, around 7 million people die every year just because of the various effects of air pollution.

4. What is the Air Quality Index?

The air quality index is measured by and used by the official pollution control authorities to show to the public how polluted the air currently is. It’s a measure that shows how polluted the air that we breathe in.

5. What are the Measures for the Control of Air Pollution?

Various methods can be undertaken to control air pollution – we can start by reducing the use of private cars, buying the electric appliances that have an energy star label, conserving energy whenever possible, and making less use of air conditioners.

6. How Can We Succeed in the Prevention of Air Pollution?

Prevention of air pollution will be a difficult task, but not an impossible one.  Apart from the individual efforts, the government authorities and the pollution control authorities should issue strict guidelines for it. Also, a good alternative should be provided for fuels and other industrial pollutants.

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Quantifying US air pollution policy: How political and regional factors influence pollutant mitigation

Affiliations.

• 1 School of Management, Lanzhou University, Lanzhou 730000, China.
• 2 Department of Decision Sciences, Western Washington University, Bellingham, WA 98225, USA.
• 3 Energy Studies Institute, National University of Singapore, 119620, Singapore, Singapore.
• 4 Department of Industrial Systems Engineering and Management, National University of Singapore, 117576, Singapore, Singapore.
• 5 Business School, Sichuan University, Chengdu 610065, China.
• PMID: 38818239
• PMCID: PMC11138116
• DOI: 10.1093/pnasnexus/pgae199

Air pollution control in the United States has evolved into a comprehensive policy system spanning from the federal to the state level over time. A unified quantitative analysis of policy intensity can shed light on the policy evolution across different levels, the influence of partisan and regional factors on policy, and the relationships with emissions of major pollutants. By harnessing the policy text of the Clean Air Act (CAA) at the federal level and State Implementation Plans (SIPs) at the state governments (1955-2020), we deployed a Natural Language Processing approach to define a policy intensity index to systematically quantify the US air policy landscape. Our findings highlight that the 1970 CAA amendment carries the most vigorous intensity as it established a holistic control system for the first time. Subsequent years witnessed a general trend of partisan polarization, eventually leading to a graduate convergence between red and blue states. Blue states demonstrated a closer alignment with federal directives and a superior efficacy in pollutant reduction. Regionally, the Northeast displays the highest overall policy intensity, and the West exhibits the highest coordination with the federal benchmarks, making these regions outperform others in air pollution control. Our study not only discusses policy implications for air pollutant reductions considering partisan and regional differences but also provides a novel measurement tool to quantify policies for assessing disparities and synergies.

Keywords: Clean Air Act; natural language processing; policy effectiveness; policy intensity; political polarization.

© The Author(s) 2024. Published by Oxford University Press on behalf of National Academy of Sciences.

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Text preprocessing and analysis procedures.

Comparing average intensity of SIPs…

Comparing average intensity of SIPs across different states. (A) is the box plot…

Policy evolution of the Clean…

Policy evolution of the Clean Air Act.

Political polarization in environmental policy.

Policy evolution of four regions.…

Policy evolution of four regions. Regional classification is based on the US Census…

• Kosack S, et al. 2018. Functional structures of US state governments. Proc Natl Acad Sci USA. 115:11748–11753. - PMC - PubMed
• Raff Z, Meyer A, Walter JM. 2022. Political differences in air pollution abatement under the Clean Air Act. J Public Econ. 212:104688.
• Hand JL, Prenni AJ, Copeland S, Schichtel BA, Malm WC. 2020. Thirty years of the Clean Air Act amendments: impacts on haze in remote regions of the United States (1990–2018). Atmos Environ. 243:117865.
• Gingerich DB, Zhao Y, Mauter MS. 2019. Environmentally significant shifts in trace element emissions from coal plants complying with the 1990 Clean Air Act amendments. Energy Policy. 132:1206–1215.
• Ridley DA, Heald CL, Ridley KJ, Kroll JH. 2018. Causes and consequences of decreasing atmospheric organic aerosol in the United States. Proc Natl Acad Sci USA. 115:290–295. - PMC - PubMed

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• Open access
• Published: 06 June 2024

Research on dust control technology and numerical simulation of conical guiding air curtain in fully mechanized excavation face

• Xin Meng 1 ,
• Qiqiang Gao 1 ,
• Jie Li 1 &
• Guoan Zhao 1  

Scientific Reports volume  14 , Article number:  12987 ( 2024 ) Cite this article

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• Energy infrastructure
• Engineering

The dust pollution caused by the operation of fully mechanized heading face poses a serious threat to the safety production of operators and working face. To reduce dust concentration at the fully mechanized heading face, this study analyzed dust samples collected from various positions to understand the particle size distribution characteristics. Based on these findings, a conical diversion air conditioning (CDAC) device was designed to create a radial air curtain for dust control in the roadway cross-section. Computational Fluid Dynamics (CFD) was then employed to investigate the airflow and particle dynamics when the cone-shaped deflector was in closed and open states. The results show that in the fully mechanized heading face, the dust distribution in the working area of the roadheader driver is relatively dense, and the dust particles with particle size ≤ 8 μm account for a large proportion. When the CDAC device is deployed, the axial airflow in the roadway is changed into a rotating airflow along the roadway wall, and an air screen is established in the working area of the roadheader driver to block the outward diffusion of dust. When the pressure air outlet is arranged 30 m away from the tunneling head, the pressure air volume is set to 400 m 3 /min, and the CDAC device can better form the air curtain barrier to block the dust particles. It provides a new method for effectively controlling the dust concentration of the fully mechanized heading face and directly ensuring the health of the roadheader driver.

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Influences of ventilation parameters on flow field and dust migration in an underground coal mine heading

Introduction.

At present, coal is one of the important energy sources for social development and industrial progress. With the continuous increase of coal seam mining depth, the degree of mechanization and automation of mines has gradually increased, and the dust pollution problem of fully mechanized working face has become increasingly prominent 1 , 2 , 3 . When the fully mechanized working face does not take any preventive measures, the dust concentration can reach 60,000 mg/m 3 . Even if certain measures are taken, the dust concentration can still be as high as 1200–1300 mg/m 3 , far exceeding the safety range required for underground mine mining 4 . When high-concentration dust particles diffuse in mines or roadways, they not only have serious explosion hazards, but also greatly increase the risk of pneumoconiosis among mine workers 5 . Long-term exposure of mine workers to high-concentration dust environment can cause incurable fibrous lesions in lung tissue, namely pneumoconiosis, which makes infected workers need lifelong medical care 6 .

China is rich in coal resources, and coal energy still occupies the main position of energy consumption structure 7 . In the process of coal resource exploitation, a large amount of dust will inevitably be produced, and the incidence of pneumoconiosis will be greatly increased. Pneumoconiosis accounts for more than 80% of new occupational cases in China, far exceeding other occupational diseases 8 , 9 . The National Health Commission of China makes statistics on the number of occupational diseases every year 10 , as shown in Fig.  1 in the past 10 years. According to Fig.  1 , although the number of new cases of pneumoconiosis in China has gradually decreased, pneumoconiosis is still one of the most harmful occupational diseases in the world. Therefore, dust pollution control during mining is still a problem that needs to be solved at this stage.

The number and proportion of occupational diseases in China from 2011 to 2021.

As an important part of coal mining, the dust control of fully mechanized heading face has also attracted much attention. Most researchers have optimized the dust suppression performance of the roadway auxiliary ventilation system by improving the air supply volume, air duct length and other parameters of the roadway auxiliary ventilation system 11 , 12 , 13 . Geng et al. 14 used Euler–Euler and Euler–Lagrange methods to investigate the diffusion characteristics of dust particles under the conditions of particle size and initial wind speed in typical coal roadways in the auxiliary ventilation system. It shows that when the initial wind speed is high, the stratification of particles with different particle sizes in the dust is more obvious. Yu et al. 15 analyzed the mechanism of dust diffusion pollution under forced exhaust ventilation in fully mechanized heading face by CFD-DEM coupling. Combined with field measurement, numerical simulation and physical experiment, Hua et al. 6 analyzed the temporal and spatial evolution law of dust pollution under the condition of blower ventilation and long pressure short pumping ventilation, and obtained the optimal distance to effectively control dust during the excavation of fully mechanized excavation face. In order to effectively suppress and prevent dust pollution, some researchers have studied the methods of dust prevention and control in coal mines. Wang et al. 16 studied the flow field characteristics inside the nozzle and near the nozzle outlet under different air supply pressures in the roadway model through numerical simulation and physical experiments, and obtained the change trend of dust suppression performance parameters with the change of air supply pressure. Wang et al. 17 put forward the integrated dust removal technology of foam and water mist. According to the characteristics of dust production in tunneling operation, a new type of flat fan foam nozzle was designed to realize the multi-stage atomization effect of air and water, effectively improve the dust removal effect and greatly reduce the dust removal cost. Liu et al. 18 designed an integrated vortex dust removal system based on the swirling jet theory. The dust removal effect of the system was analyzed and tested by numerical simulation and field experiments. The results show that the designed system has better control and removal effect for smaller dust particles. The concentration of total dust and inhaled dust in the air is reduced to 10 mg/m 3 .

In summary, while dust control technologies for fully mechanized heading faces have made significant progress, current research primarily focuses on the cutting position of the road header rather than directly ensuring the health of the road header operators. To effectively reduce dust concentration in the heading face, it is essential to understand the dust particle distribution characteristics at different positions within the heading face. This study collected dust samples from various locations within the fully mechanized heading face and used image analysis techniques to determine the particle size distribution characteristics at these positions. Based on these characteristics, a CDAC device was designed to create a radial air curtain for effective dust control across the roadway cross-section. Numerical simulations were then conducted to explore the optimal minimum distance of the air outlet when the deflector device is closed and the optimal airflow rate when the deflector device is open. The simulation results were validated against field data. This study provides a new method for effectively controlling dust concentration in fully mechanized heading faces and directly safeguarding the health of road header operators.

Distribution characteristics of dust particles in fully mechanized heading face

Dust is not only a kind of solid microparticles that can float in the air for a long time, but also a kind of dispersion system called aerosol. The dispersed phase is solid microparticles, and the dispersion medium is air 19 , 20 , 21 . Dust is defined from the perspective of explosion, and generally refers to rock particles with a particle size (the average cross-sectional diameter of the dust particles) of 0.75–1 mm or less 22 , 23 ; rock powder is defined from the perspective of industrial hygiene, which generally refers to rock dust particles with particle size below 10–45 μm 24 , 25 .

A large amount of dust emitted during the production process is called productive dust 26 , 27 . Mine dust belongs to a type of productive dust, which is the general term of various rock and mineral particles produced in the process of mine construction and production. Coal mine dust is the general term of coal dust, dust and other toxic and harmful dust. In addition, there are a small amount of metal particles, artificial organic dust (such as soot) generated during blasting and artificial inorganic dust (such as cement dust) generated during arching and shotcrete construction in coal mines 28 .

Dust sampling in production process

During actual production at the Yongming Coal Mine heading face, fresh air is supplied to the heading face through a forced ventilation system. This ensures that dust particles generated at the heading face are expelled from contaminated air, thereby achieving dust suppression. Consequently, dust samples are collected from various production processes at the fully mechanized heading face. According to the dust measurement points specified by the "Coal Mine Safety Regulations," critical positions at the heading face are sampled. Six sampling points are set up at the fully mechanized heading face: the heading face (1#), the operator's position (2#), the leeward side of the transfer machine (3#), the leeward side of the telescopic belt conveyor (4#), 100 m from the heading face (5#), and 200 m from the heading face (6#). The specific sampling locations are shown in Fig.  2 . Each sampling point is measured three times per sampling operation.

Dust sampling point layout diagram of fully mechanized excavation face. 1# sampling point is at the mining position of the heading face; 2# sampling point is at the location where the operator controls the heading machine; 3# sampling point is on the leeward side of the transfer machine, which is responsible for transferring the rock fragments generated at the heading face; 4# sampling point is on the leeward side of the telescopic belt conveyor, which is responsible for transporting the rock fragments; 5# sampling point is 100 m from the heading face; and 6# sampling point is 200 m from the heading face.

Determination method of dust particle size distribution

The physical and chemical characteristics of dust in fully mechanized heading face mainly include dust concentration, particle size, dispersion and other parameters. The specific measurement method is shown in Fig.  3 . Dust concentration was measured using a full-dust pre-trap in the mine dust sampler (CCZ-20A) to form dust samples. Before collecting samples, select the sampling location and securely fix the dust sampler horizontally on the tripod platform. Install the pre-collector with the filter (Φ 75 mm or Φ 40 mm perchloroethylene fiber filter) firmly on the sampler head connector, ensuring the pre-collector's inlet is positioned within the dust-laden airflow. When collecting samples, the sampling time is preset according to the type, concentration and operation of dust on site. Generally, the sampling time is 20–25 min, and the place with higher dust concentration is generally preset for 2–5 min. After the sample collection, remove the filter membrane and gently place it in the corresponding sample box. Dry the filter membrane using a drying oven, and after the process is completed, weigh it using an electronic balance and record the weight.

Schematic diagram of the method for measuring the physical and chemical properties of dust in fully mechanized excavation face. ( a ) Experimental pre-processing; ( b ) microscopic particle image analyzer; ( c ) laser particle size analyzer.

In order to further understand the actual situation of dust particle size distribution in each process of fully mechanized heading face, the proportion of respirable dust in the dust generated on site was investigated. Dust was obtained on the site of fully mechanized heading face in Yongming Coal Mine, and the frequency distribution data of particles (the percentage of each particle size interval) were obtained by laser particle size analyzer (Mastersizer 3000). The role of the microscopic particle image analyzer (Winner 99) is to use the image processing software to perform a series of processing on the collected original image, and then the particle size analysis data can be obtained.

Analysis of dust particle size distribution characteristics of each process

The dust particles generated during various processes of the fully mechanized mining face were analyzed using a Micro Particle Image Analyzer (Winner 99) to obtain images of the dust particles. The images were processed using a binarization method to extract the distribution characteristics of the dust particles, as shown in Fig.  4 . Subsequently, a Laser Particle Size Analyzer (Mastersizer 3000) was employed to determine the particle size characteristics of the dust particles.

Grain size analysis diagram of each process in fully mechanized excavation face. ( a ) Heading face; ( b ) Driver 's office; ( c ) The downwind side of the loader; ( d ) The downwind side of the telescopic belt conveyor; ( e ) 100 m from the heading face; ( f ) 200 m away from the heading face. The green image represents the microscopic particle image, the black and white image depicts the binarized particle image, and the histogram illustrates the frequency distribution of particle diameters.

According to Fig.  4 , the particle size of dust particles produced in each process of fully mechanized heading face is different. It can be seen that the dust distribution at 1 # (heading face) and 2 # (driver's position) is denser. The dust distribution at 3 # (downwind measurement of loader) and 4 # (downwind side of telescopic belt conveyor) is more dispersed than that at 1 # (heading face) and 2 # (driver's position). The dust distribution at 5 # (100 m away from heading face) and 6 # (200 m away from heading face) is more dispersed. In general, the dust concentration distribution at 2 # (driver 's position) is the densest, indicating that it poses a great threat to the health of roadheader drivers.

In the various processes of the fully mechanized working face, the particle size of dust particles mainly ranges between 6 and 8 μm. However, the diameter of breathable dust particles is consistently 7.07 μm 29 . Therefore, 8 μm is selected as the particle size threshold to effectively categorize breathable dust particles in the dust based on frequency distribution calculations. The results are presented in Table 1 .

According to Table 1 , the frequency distribution of 8 μm coal dust generated at 2 # site (driver 's place) was 10.65%, and the cumulative distribution of particle size ≤ 8 μm even reached 70.2%. The cumulative distribution of particle size ≤ 8 μm in 1 # site (heading face) and 3 # site (underwind side of loader) reached 40.4% and 36.8%, but its D 50 was 11.7 μm and 12.2 μm, indicating that the dust particle size produced by the process of 1 # site (heading face) and 3 # site (underwind side of loader) was larger, and the proportion of respirable dust produced by the other processes was about 40%. Therefore, in order to ensure the health of the driver of the fully mechanized tunneling face, it is necessary to focus on dust prevention and control at this position.

Dust control technology of conical diversion air curtain in fully mechanized heading face

The cone-shaped diversion and air conditioning device is a kind of wall-attached effect of air flow, which changes the axial air flow supplied by the original forced air duct to the fully mechanized heading face into the rotating air flow along the roadway wall, and blows to the surrounding wall of the roadway and the whole roadway section at a certain rotating speed to form an air wall, and continuously advances to the fully mechanized heading face. Under the combined action of the axial velocity generated by the dust-containing air flow inhaled by the dust collector, a spiral linear air flow with high function is formed, and an air screen is established in front of the working area of the roadheader driver to block the outward diffusion of dust, blocking the dust generated during the operation of the roadheader. It is purified by suction into the dust collector through the dust suction duct without outflow, thus improving the dust collection efficiency of the fully mechanized excavation face.

The conical diversion air regulating device for fully mechanized heading face (see Fig.  5 ) includes a cylindrical cylinder, a conical cylinder, a conical deflector, a regulating switch, a three-way air guide cover, an air inlet and an air outlet. Among them, the three-way wind guide hood is connected with the outer wall of the cylindrical cylinder. The three-way wind guide hood is composed of three wind guide hoods in different directions. The wind guide hood near the outlet is 60° with the cylindrical cylinder, the middle wind guide hood is 90° with the outer wall of the cylindrical cylinder, and the wind guide hood near the inlet is 120° with the cylindrical cylinder. The device is installed at the outlet position of the compressed air duct in the heading face, which is connected with the outlet of the compressed air duct. The conical diversion air regulating device can be closed and expanded by adjusting the switch.

Design and installation diagram of conical diversion air-conditioning device. ( a ) Installation design of CDAC device; ( b ) The structure design of CDAC device; ( c ) The closed state of the CDAC device; ( d ) The expansion state of the CDAC device; ( e ) Cross-sectional airflow flow of the CDAC device.

When the CDAC device is in a closed state, the internal pressure air flow of the cylindrical tube passes through the conical tube and flows out from the air outlet, as shown in Fig.  5 c. When the conical diversion air-conditioning device is in the state of expansion, the conical diversion air-conditioning device forms a wind-shield surface in the cylinder body with an area smaller than the inner diameter of the cylinder body, as shown in Fig.  5 d. The air flow passing through the pressure air flow in the cylinder body is effectively blocked, so that the pressure air flow flows out from the three-way air guide hood, and the pressure air flow in the pressure air cylinder is changed into a three-way dust control airflow field flowing to the fully mechanized heading face. The dust produced by the head-on cutting of the fully mechanized heading face is effectively controlled.

A hybrid ventilation system employing prolonged pressure and short suction is utilized during the commencement of the fully mechanized tunneling face. It is required that the distance between the outlet of the pressure duct and the tunneling head should not exceed \(5\sqrt S\) (where S represents the cross-sectional area of the tunnel). The distance of the dust suction port from the tunneling head is calculated based on empirical formulas \(1.5\) \(\sqrt S\) \(\sqrt S\) 30 . As the face advances, the conical diversion air regulation device is deployed, directing the airflow from the side of the device towards the face, as illustrated in Fig.  5 e. During face support operations, the conical diversion air regulation device is closed, directing the airflow directly toward the face. To accommodate the specific conditions of the full mechanized tunneling face, the conical diversion air regulation device is mounted on a dedicated movable device, allowing it to move synchronously with the tunneling machine and thus ensuring compliance with the layout requirements of the ventilation and dust removal system.

Numerical simulation study on dust control of conical diversion air curtain in fully mechanized tunneling face

The flow and flow field distribution of roadway airflow directly affect the distribution of dust concentration in fully mechanized heading face. Since the 1980s, some researchers have begun to carry out experimental research on the distribution of air flow in fully mechanized heading face 31 , 32 , 33 . At present, with the development of computer technology, computational fluid dynamics simulation of roadway airflow and the distribution of dust particles has been widely used 20 , 34 , 35 .

Mathematical model

In the construction process of fully mechanized tunneling face, the diffusion phenomenon of dust particles generated by the tunneling process of roadheader under the action of airflow belongs to the gas–solid two-phase flow model. In this paper, the fluid mechanics equations of particle phase based on the theory of particle phase dynamics and the conservation equations of gas phase constitute the multiphase control equations of laminar gas phase and laminar particle phase, and then simulate the diffusion process of dust particles driven by airflow in the full mechanical tunneling face. In the fully mechanized heading face, air is regarded as a continuous medium, and dust particles are regarded as discrete items. Due to a lack of reliable correlation, the model needs to pay more attention to the influence of particle-phase turbulence on the particle temperature and gas-particle drag equations. With the closure of the above model, the steady-state governing equations for three-dimensional turbulent multiphase flow in cylindrical coordinates can be expressed in a general form: convection term = diffusion term + source term. The specific mathematical models utilized are represented by Eqs. ( 1 ) to ( 2 ) 36 , 37 .

The general expression of the gas phase control equations is:

The general expression of the particle phase control equations is:

In the fully mechanized mining face, dust particles are subject to various forces such as resistance, gravity, buoyancy, Saffman force, Magnus force, thermophoretic force, adhesion force, Basset force, added mass force, and pressure gradient force. However, in this numerical simulation of airflow and particle dynamics in the mining face, the density of dust particles is much greater than that of air, and the effects of adhesion force, Basset force, and buoyancy are negligible compared to other forces. Furthermore, since the volume of dust particles in the fully mechanized mining face is less than 10% of the computational domain volume, the reactive force of dust particles on airflow can be neglected. Only the stabilizing effect of airflow on dust particles needs to be considere 2 , 36 , 38 .

This study will consider the Saffman force, Magnus force, pressure gradient force, resistance, and gravity. The Saffman force primarily refers to the force responsible for lifting particles and the pressure difference caused by the flow velocity on both sides of the dust particles, as shown in Eq. ( 3 ) 39 .

where B is the experimental constant; d p is the radius of the particle; ρ is the density of the gas phase; η is the viscosity of the gas phase; u p is the velocity of the gas phase, u s is the velocity of the solid phase; ∇ is the nabla operator.

When the fluid is in a low Reynolds number turbulence state, particles in the flow field experience rotational forces, known as the Magnus force. Assuming a rotational angular velocity of ω for the particles in the airflow, the Magnus force equation is as follows:

Under typical conditions, due to the pressure gradient along the direction of gas flow in the flow field, there will be a particular force acting on the transport diffusion of spherical particles, as shown in Eq. ( 5 ).

where d p / d x represents the pressure gradient in the direction of gas flow.

Dust particles experience a certain resistance in the gas-phase flow field and particle field, which can be expressed as:

where A p represents the particle's projection perpendicular to the airflow direction, and C d represents the drag coefficient.

Geometric models and parameter settings

In order to accurately numerically simulate the airflow condition, dust distribution and movement patterns in the fully utilizing the long-pressure-short-extraction ventilation method, a three-dimensional physical model of the fully mechanized mining face was constructed using three-dimensional modeling software based on the actual conditions of the 3201 mining face in Yongming Coal Mine of Shaanxi Province, The constructed physical geometry model was simplified and comprised six significant components: roadway, shearer (including body, cutting part, walking track, and scraper), blowing fan, suction fan, bridge-type shuttle car, and belt conveyor. The specific geometric model dimensions are detailed in Table 2 . The positive direction of the x-axis denotes the direction from the cutting head to the end of the roadway, the positive direction of the y-axis represents the direction from one sidewall of the mining face to the other, and the positive direction of the z-axis represents the direction from the roadway floor to the roof.

Subsequently, the geometric physical model was subjected to grid partitioning using ICEM meshing software. The geometric model and grid partitioning are illustrated in Fig.  6 , resulting in a total of 1,034,513 grids. The grid quality ranges from a minimum of 0.351239 to a maximum of 0.99931, with an average value of 0.916247, all meeting the requirements for simulation 2 . Finally, the grid-partitioned physical model was imported into the ANSYS Fluent solver to simulate and compute the airflow conditions, dust distribution, and movement patterns during the long-pressure-short-exhaust ventilation method employed in the fully mechanized mining face.

The model diagram of fully mechanized heading face. ( a ) Simulation model; ( b ) Grid division; ( c ) Transverse Interface.

A cone-shaped diversion and air conditioning device is installed on the air duct of the fully mechanized tunneling face. The air conditioning ratio of the cone-shaped diversion air curtain dust control device is set to be 1:9 when the deflector is deployed. 10% of the air pressure is blown out from the axial air outlet, and 90% of the air is blown out from the air outlet of the three-way air guide cover.

Boundary condition setting

This study mainly simulates the ventilation condition of the closed and unfolded state of the CDAC device. When the conical diversion air regulating device is in a closed state, similar to the situation when the conical diversion air regulating device is not installed, the outlets of the pressure air duct and the exhaust air duct are defined as 'Velocity_Inlet', and the end of the roadway is defined as 'Pressure_Out'. When the conical diversion air regulating device is in the unfolded state, the outlet of the pressure air duct and the outlet of the conical diversion air regulating device are defined as 'Velocity_Inlet'.

During the model setup, two assumptions were made: (1) the continuous phase airflow is treated as an ideal gas, and (2) the temperature field remains constant. In the production process of the fully mechanized mining face, the particle size range of generated particles is between 0.85 and 84.3 µm. Therefore, this simulation ignores the influence of particle shape on particle motion and adopts uniform spherical particles 2 , 36 . However, in the actual operation of the fully mechanized mining face, the number of generated particles is extremely large (exceeding 10e9), far exceeding the computational capacity of computer solvers. Therefore, to compute numerical simulation results within the capabilities of existing computers, a finite number of particle motions were set to represent the motion characteristics of all actual particles with specific parameters, as shown in Table 3 .

Results and discussion

Closure state of cdac device, air flow field.

To investigate the influence of the distance between the air inlet and the cutting head on the migration of the airflow field with the cone-shaped air diversion device in the closed state and to determine the minimum critical distance required to form an effective axial dust control airflow curtain. Considering the actual operational conditions of the fully mechanized mining face, the total air volumes of the air inlet and exhaust fan were defined as 300 m 3 /min and 240 m 3 /min, respectively. The distances of the air inlet from the cutting head were set at 5 m, 10 m, 15 m, 20 m, 25 m, and 30 m. When the cone-shaped air diversion device is closed, the situation is similar to when no cone-shaped air diversion device is installed. Therefore, the closed state of the cone-shaped air diversion device was used as the baseline for research before installation. The variation of the airflow field with different distances between the air inlet and the working face is depicted in Fig.  7 .

Simulation results of air flow field migration at different distances from the pressure tuyere to the head. A cross-sectional analysis was conducted at the position of X = 5 m (cutting machine operator's location). ( a ) 5 m; ( b ) 10 m; ( c ) 15 m; ( d ) 20 m; ( e ) 25 m; ( f ) 30 m.

According to Fig.  7 a–f, it can be observed that as the distance between the air inlet and the mining face increases gradually from 5 to 30 m, a airflow field gradually forms flowing along the negative direction of the X-axis. With the increase in distance between the air inlet and the mining face, the axial airflow field moves further away from the mining face. When the distance between the air inlet and the mining face is between 5 and 25 m, no axial airflow field is formed, and the axial airflow field exists only at the mining face. However, when the distance between the air inlet and the mining face is 30 m, the axial airflow field begins to form, with the farthest distance from the mining face being 8.36 m, and the airflow gradually becomes more uniform. Furthermore, the minimum distance for the formation of the axial airflow field was further analyzed at the cutting machine operator's position (i.e., X = 5 m). When the distance between the air inlet and the mining face is between 5 and 25 m, the airflow field at the cutting machine operator's position is chaotic and unevenly distributed, unable to form a uniform and stable axial airflow field. However, when the distance between the air inlet and the mining face is 30 m, the airflow field at the cutting machine operator's position is relatively uniform and free from turbulent flow, with the airflow velocity decreasing from a maximum of 15.7 m/s at the air inlet to approximately 0.42 m/s. This indicates that as the distance between the air inlet and the mining face increases, the injected airflow diffuses more fully and evenly in the roadway. However, as the distance between the air inlet and the mining face increases, some of the outflowing airflow begins to lose momentum, resulting in a decrease in flow velocity and a deviation in flow direction, forming a vortex airflow field and ultimately resulting in an axial airflow field flowing along the negative direction of the X-axis.

Air flow-dust particle two-phase flow field

Based on Fig.  8 a–f, it can be observed that as the distance between the air inlet and the mining face increases, the aggregation range of dust particles tends to decrease. When the distance between the air inlet and the mining face is 5 m, the diffusion distance of dust particles with concentrations above 50 mg/m 3 is 16.5 m. As the distance increases to 25 m, the diffusion distance gradually decreases to 11.2 m. When the distance reaches 30 m, the diffusion distance sharply decreases to 5.8 m for dust particles with concentrations above 50 mg/m 3 . Further analysis at the cutting machine operator's position (X = 5 m) reveals that within the range of 5–25 m between the air inlet and the mining face, the dust concentration fluctuates between 162.5 and 237.8 mg/m 3 . When the distance between the air inlet and the mining face is 30 m, the dust concentration decreases to 129.8 mg/m 3 . This indicates that airborne dust transport simulation results are consistent with airflow field simulations. The minimum distance between the air inlet and the mining face required to form an axial airflow field is 30 m. At this point, an airflow curtain flows along the negative X-axis direction, continuously reducing the diffusion distance of dust particles with concentrations above 50 mg/m 3 , effectively controlling the movement of dust particles to maintain the axial airflow field. However, the cutting machine operator's position remains in an environment with relatively high dust concentration, posing a severe health risk to the operator.

The overall diagram of the simulation results of air-borne dust flow field migration at different distances between the pressure tuyere and the tunneling head. ( a ) 5 m; ( b ) 10 m; ( c ) 15 m; ( d ) 20 m; ( e ) 25 m; ( f ) 30 m.

Model validation

To validate the feasibility of the constructed geometric model and boundary conditions, measurements were taken at the 3201 mining face of Yongming Coal Mine. In the 3201 mining face, the air supply duct had a supply volume of 300 m 3 /min, and the distance from the air supply opening to the face of the mining face was set at 5, 10, 15, 20, 25, and 30 m, respectively. The exhaust duct had an exhaust volume of 240 m 3 /min, and the distance from the exhaust opening to the face of the mining face was set at 3 m. The operator position of the cutting machine was selected as the measurement point. The airflow at this position was measured using a handheld air velocity sensor (TSI8455), while the dust concentration was measured using an explosion-proof direct-reading mine dust detector (CCZ-1000). The dust concentration at a distance of 5 m from the face was taken as the source of dust concentration, as shown in Fig.  9 .

Curve fitting of numerical simulation and experimental results for airflow and particle field. ( a ) Airflow field; ( b ) particle field.

According to Fig.  9 a,b, it can be observed that at the position of the cutting machine operator, the results obtained from numerical simulations exhibit a high degree of fit with the experimentally measured results. The coefficient of determination R 2 for the airflow field is 0.97, and for the particle field is 0.98. This indicates that the numerical simulation results are consistent with the experimental measurements for airflow and particle fields. However, due to various interfering factors affecting the experimental data, there is a certain degree of error between the numerical simulation results and the experimental measurements. The relative error range for the airflow field is 1.25–14.14%, and for the particle field is 4.67–10.66%. As the maximum relative error range for both fields is less than 15% 2 , the numerical simulation results of this study are considered accurate, providing valuable data support for investigating the airflow and particle fields when the conical diversion adjustment device is deployed.

Expansion state of CDAC device

The conical diversion adjustment device is deployed in the expanded state to better reduce particle concentration at the cutting machine operator's position. This divides the axial airflow in the pressure duct into 10% axial airflow and 90% radial airflow, forming a radial airflow field to lower the particle concentration at the cutting machine operator's position. Therefore, based on the airflow field distribution characteristics, when the conical diversion adjustment device is closed, the radial air outlet of the conical diversion adjustment device is set at a distance of 30 m from the cutting face. To meet the ventilation requirements at the cutting machine operator's position, a ventilation duct of 20 m in length will be installed at the axial air outlet of the conical diversion adjustment device to supply air.

The airflow rate is a crucial factor influencing the formation of radial air curtains by the conical diversion adjustment device. Appropriate airflow rates can stabilize the air curtain and achieve optimal dust prevention performance. Considering the actual operating conditions of the fully mechanized mining face, based on the numerical simulation results when the conical diversion adjustment device is closed, we investigate the airflow and particle fields with different airflow rates in the pressure duct when the conical diversion adjustment device is deployed. The airflow rates in the pressure duct are set to 200 m 3 /min, 250 m 3 /min, 300 m 3 /min, 500 m 3 /min, and 600 m 3 /min, while the total airflow rate of the exhaust duct is set to 240 m 3 /min.

According to Fig.  10 a–e, it can be observed that with the gradual increase in the airflow rate, the stability of the radial airflow field initially increases and then decreases. When the airflow rate is 200 m 3 /min, the airflow velocity at the radial air outlet of the device is 9.76 m/s. When the airflow rate is increased to 250 m 3 /min, the airflow velocity at the radial air outlet of the device increases to 12.34 m/s. As the airflow rate increases to 300 m 3 /min, the airflow velocity at the radial air outlet reaches 19.21 m/s. However, when the airflow rate is increased to 400 m 3 /min and 600 m 3 /min, the airflow velocity at the radial air outlet decreases to 11.85 m/s and 5.43 m/s, respectively. With the increasing airflow rate, it becomes more difficult to form a uniformly controlled dust airflow field along the negative X-axis direction at the section where the cutting machine operator is located (X = 5 m). When the airflow rates are 200 m 3 /min, 250 m 3 /min, and 300 m 3 /min, a controlled dust airflow field can be formed along the negative X-axis direction. However, when the airflow rate increases to 600 m 3 /min, in the area 0–0.8 m above the bottom of the section where the cutting machine operator is located, the airflow is reduced, and some airflow flows towards the sidewalls of the tunnel, failing to form a uniformly controlled dust airflow field along the negative X-axis direction.

The overall diagram of the simulation results of the flow field migration of different pressure air volume after the expansion of the CDAC device. ( a ) 200 m 3 /min; ( b ) 250 m 3 /min; ( c ) 300 m 3 /min; ( d ) 400 m 3 /min; ( e ) 600 m 3 /min.

This indicates that after the conical diversion adjustment device is deployed, 90% of the airflow through the radial air outlet forms an impact jet, covering the sidewalls of the tunnel and forming a wall-attached dust control radial airflow field. The remaining 10% of the airflow discharged through the axial air outlet, due to its similar velocity to the surrounding airflow, does not create a suction effect with the surrounding air, allowing the airflow to continue flowing along the negative X-axis direction and spreading towards the sidewalls of the tunnel with the exhaust duct. However, as the airflow rate increases, the high-speed airflow discharged through the axial air outlet creates an impact jet on the cutting face, resulting in turbulent airflow in the tunnel.

After deploying the conical diversion adjustment device, simulations were conducted to investigate the dispersion of airborne dust particles under different airflow rates, as illustrated in Fig.  11 . As shown in Fig.  11 a–e, with the increase in airflow rate, the dispersion distance of high-concentration dust particles (> 50 mg/m 3 ) gradually decreases. For instance, when the airflow rate is 200 m 3 /min, the dispersion distance of high-concentration dust particles is 6.8 m. As the airflow rate increases to 250 m 3 /min, the dispersion distance decreases from 6.8 to 5.6 m. Further, at an airflow rate of 300 m 3 /min, the dispersion distance reduces to 5.0 m. Similarly, at higher airflow rates of 400 m 3 /min and 600 m 3 /min, the dispersion distances decrease to 3.3 m and 3.2 m, respectively. At the driver's location (X = 5 m), the dust concentration also decreases with increasing airflow rate. For example, at an airflow rate of 200 m 3 /min, the dust concentration is approximately 201.5 mg/m 3 . However, as the airflow rate increases to 300 m 3 /min, the dust concentration sharply decreases to 18.8 mg/m 3 . Similarly, at 400 m 3 /min airflow rates and 600 m 3 /min, the dust concentration gradually decreases to 18.3 mg/m 3 and 18.1 mg/m 3 , respectively.

The overall diagram of the simulation results of the flow field migration of airborne dust with different pressure air volume after the deployment of the conical diversion air regulating device. ( a ) 200 m 3 /min; ( b ) 250 m 3 /min; ( c ) 300 m 3 /min; ( d ) 400 m 3 /min; ( e ) 600 m 3 /min.

This indicates that changes occur in the airflow field at the mining face after deploying the conical diversion adjustment device. A radial dust control airflow field is formed at the radial air outlet position, maintaining the dispersion distance of high-concentration dust particles near the cutting machine operator. Due to the diversion of 10% of the airflow through the axial air outlet, when the airflow rate is relatively low, the dispersion distance of high-concentration dust is shorter, leading to a high dust concentration environment around the cutting machine operator. However, at the critical airflow rate, the formation of an axial airflow field along the negative X-axis direction leads to a sharp decrease in the dust concentration near the cutting machine operator. When the airflow rate exceeds the critical airflow rate, the axial airflow continuously impacts the mining face, effectively reducing the dust concentration near the cutting machine operator by aggregating high-concentration dust particles.

In summary, after deploying the conical diversion adjustment device, the airflow rate controls the formation of both axial and radial airflow fields. At an airflow rate of 300 m 3 /min, the airflow field is relatively stable and uniform, with the maximum radial airflow velocity, forming a stable radial airflow curtain. This effectively impedes the dispersion movement along the positive X-axis direction. The axial airflow curtain formed by the axial airflow field controls the dust particle concentration near the cutting machine operator, ensuring the operator's health and safety.

Conclusions

In order to effectively control the dust concentration of the fully mechanized heading face and directly protect the health of the driver of the roadheader, this paper studies the physical and chemical characteristics of the dust in each process of the heading face, and proposes a cone-shaped diversion air curtain dust control technology. The numerical simulation is used to explore the dust control ability of the cone-shaped diversion air curtain. The specific conclusions are as follows:

The particle size of dust particles produced in each process of fully mechanized heading face is different. The dust concentration at the driver’s place is large, and the cumulative distribution of particle size ≤ 8 μm is as high as 70.2%. Therefore, it is necessary to focus on the prevention and control of this location.

Based on the wall-attached effect of airflow, a conical diversion and air-regulating device is designed, which can change the axial airflow in the roadway of fully mechanized heading face into a rotating airflow along the roadway wall, and blow it to the surrounding wall of the roadway and the whole roadway section at a certain rotation speed. An air screen that can block the outward diffusion of dust is established in front of the working area of the roadheader driver.

CFD is used to simulate the airflow field and the two-phase flow field of airflow particles when the cone-shaped air-conditioning device is closed and displayed. It is determined that the conical diversion air regulating device is installed at the pressure air outlet, and the distance between the pressure air outlet and the heading head is 30 m, which can better form the air screen. When the conical diversion air regulating device is in the unfolded state, with the increase of the compressed air volume, the diffusion distance of high concentration dust decreases continuously, and the dust concentration at X = 5 m driver also decreases gradually. When the optimal pressure air volume is 400 m 3 /min, the air curtain barrier can be better formed to block the dust particles.

Data availability

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

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Acknowledgements

The research was supported by the Key project of Heilongjiang Provincial Natural Science Foundation (Project No.ZD2021E006), Simultaneously, we greatly appreciate the Editors and anonymous who gave helpful comments and suggestions, which will supply more scientific guidance for our research.

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Meng, X., Gao, Q., Li, J. et al. Research on dust control technology and numerical simulation of conical guiding air curtain in fully mechanized excavation face. Sci Rep 14 , 12987 (2024). https://doi.org/10.1038/s41598-024-63881-4

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Impact of indoor air pollution on DNA damage and chromosome stability: a systematic review

• Kazensky, Luka
• Matković, Katarina
• Gerić, Marko
• Žegura, Bojana
• Pehnec, Gordana
• Gajski, Goran

Indoor air pollution is becoming a rising public health problem and is largely resulting from the burning of solid fuels and heating in households. Burning these fuels produces harmful compounds, such as particulate matter regarded as a major health risk, particularly affecting the onset and exacerbation of respiratory diseases. As exposure to polluted indoor air can cause DNA damage including DNA sd breaks as well as chromosomal damage, in this paper, we aim to provide an overview of the impact of indoor air pollution on DNA damage and genome stability by reviewing the scientific papers that have used the comet, micronucleus, and γ-H2AX assays. These methods are valuable tools in human biomonitoring and for studying the mechanisms of action of various pollutants, and are readily used for the assessment of primary DNA damage and genome instability induced by air pollutants by measuring different aspects of DNA and chromosomal damage. Based on our search, in selected studies (in vitro, animal models, and human biomonitoring), we found generally higher levels of DNA strand breaks and chromosomal damage due to indoor air pollutants compared to matched control or unexposed groups. In summary, our systematic review reveals the importance of the comet, micronucleus, and γ-H2AX assays as sensitive tools for the evaluation of DNA and genome damaging potential of different indoor air pollutants. Additionally, research in this particular direction is warranted since little is still known about the level of indoor air pollution in households or public buildings and its impact on genetic material. Future studies should focus on research investigating the possible impact of indoor air pollutants in complex mixtures on the genome and relate pollutants to possible health outcomes.

• Indoor air quality;
• Genome damage;
• Comet assay;
• Micronucleus assay;
• γ-H2AX assay;
• Health risk

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Santa Barbara’s Air Pollution Control District reaches $1.3 million settlement with Lompoc cannabis processing facility

SANTA BARBARA COUNTY, Calif. – On Thursday, the Santa Barbara County Air Pollution Control District (SBCAPCD) announced that Central Coast Agriculture has agreed to a $1.3 million settlement over penalties issued to the company's cannabis manufacturing facility in Lompoc.

Between 2020 and 2023, staff with the SBCAPD documented multiple air quality violations and issued several air quality notices of violations to Central Coast Agriculture detailed the county-based pollution regulator in a press release about the settlement.

Of the $1.3 million settlement , $200,000 will be sent to the SBCAPCD's Clean Air Fund which funds projects intended to improve air quality in the Lompoc community shared the SBCAPCD.

Additionally, an undisclosed portion of the settlement will be used towards an expansion of surveillance of post-harvest cannabis operations across the county with the remainder of the settlement going into the SBCAPCD's fund for future use shared the SBCAPCD.

According to the settlement, Central Coast Agriculture is required to submit the full civil penalty no later than Jun. 7, 2024.

In October of 2020, inspectors with the SBCAPCD issued a notice of violation to Central Coast Agriculture for installing and operating a cannabis manufacturing facility in Lompoc without a proper SBCAPCD permit and without the required emissions control systems.

Inspectors with the SBCAPCD conducted a surveillance inspection of the facility to collect information for the October violations detailed the SBCAPCD in a press release about the settlement.

After the October 2020 notice of violation was issued, the SBCAPCD issued nine more notices of violation at the Central Coast Agriculture Lompoc facility as well as 17 notices of violation for two of the company's facilities in the Buellton area shared the SBCAPCD.

According to the SBCAPCD, the Lompoc facility, "emitted significant amounts of regional ozone precursor pollutants" since the initial October 2020 notice of violation.

On Nov. 29, 2023, the SBCAPCD issued a final permit for Central Coast Agriculture's Lompoc facility following the implementation of emissions control requirements.

Under that final permit, Central Coast Agriculture Inc. installed a solvent recapture system and is expected to install emissions control equipment at their Lompoc facility by September of this year explained the SBCAPCD.

The SBCAPCD expects the recapture and control systems to reuse more than 97 percent of the solvent used for cannabis production at the Lompoc facility instead of being emitted into the atmosphere.

The SBCAPCD shared that the solvent recapture system, developed and proposed by Central Coast Agriculture, is considered unique to the facility and may set the groundwork for use at other cannabis production facilities.

"We are thankful to have reached a settlement, and more importantly worked with CCA [Central Coast Agriculture Inc.] to reach compliance with air quality regulations for their manufacturing operations," stated Aeron Arlin Genet, Executive Director for the SBCAPCD. "The magnitude of this settlement reflects the significance of the violations and the amount of emissions over 3 years. The Clean Air Fund portion of this settlement will be used on other projects throughout the Lompoc community to reduce emissions and improve air quality."

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Methodological Support of Air Pollution Monitoring System

• First Online: 09 August 2023

Cite this chapter

• Artur Zaporozhets   ORCID: orcid.org/0000-0002-0704-4116 3 ,
• Vitalii Babak   ORCID: orcid.org/0000-0002-9066-4307 3 ,
• Oleksandr Popov   ORCID: orcid.org/0000-0002-5065-3822 4 ,
• Leonid Scherbak   ORCID: orcid.org/0000-0002-1536-4806 3 &
• Yurii Kuts   ORCID: orcid.org/0000-0002-8493-9474 5  

Part of the book series: Studies in Systems, Decision and Control ((SSDC,volume 481))

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In this chapter, a methodology for air pollution monitoring using spatially branched wireless sensor networks is formed, based on 3 directions of scientific and practical foundations: theoretical, methodological, and hardware/software. As an element of an integrated control system for complex technical objects, a hierarchical structure of the air pollution monitoring system is proposed within the framework of the Smart Energy concept. A feature of this structure is the formation of relevant data at different hierarchical levels and access to them by the relevant user groups. The goals, objectives and requirements for the data of the air pollution monitoring system are formed. It is shown that the objectives of air pollution monitoring are unique for various networks, and can be formed with taking into account a significant number of factors. As an integral part of the methodology, mathematical models of the air pollution field are proposed in the form of a vector random field, non-uniform in spatial arguments, non-stationary in time, and which depends on the influence of various factors. The use of mathematical models of this type makes it possible to carry out studies with the determination of spatio-temporal characteristics during monitoring in various limited areas of space at finite time intervals. This provides an opportunity for further comparative analysis of monitoring results in order to verify the adequacy of the proposed models, predict the dynamics of changes in the main characteristics of control objects in space and time.

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Zaporozhets, A., Babak, V., Popov, O., Scherbak, L., Kuts, Y. (2023). Methodological Support of Air Pollution Monitoring System. In: Zaporozhets, A. (eds) Systems, Decision and Control in Energy V. Studies in Systems, Decision and Control, vol 481. Springer, Cham. https://doi.org/10.1007/978-3-031-35088-7_41

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San Diego County to purchase air purifiers for South Bay communities impacted by sewer gas

San Diego Congressional leaders introduce amendment to establish a new federal program to combat cross-border pollution

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San Diego County will provide air purifiers to people who live and work near where sewage and toxic chemicals spill over the U.S.-Mexico border from Tijuana and have reported feeling ill from noxious odors.

On Tuesday, the county Board of Supervisors unanimously approved Chairperson Nora Varga’s request to buy up to $100,000 worth of equipment and develop a program to distribute them to those in need.

“Ambient odors coming from the (Tijuana) river have had a negative impact on the quality of life of South County residents, including our small businesses,” Vargas said in a statement. “This is very concerning, but as a board member for the (Air Pollution Control District), I know that obtaining air purifiers for the communities affected by the pollution will help them immediately mitigate odors and improve living conditions, especially during the summer.”

Residents and businesses in South County’s southernmost communities, such as Imperial Beach, Nestor, San Ysidro, Otay Mesa West and the Tijuana River Valley, have reported constant rotten egg odors affecting their health and way of life. Many have said they suffer from chronic coughs, migraines, asthma and nausea. They have said their symptoms tend to stop when leaving their neighborhoods.

To mitigate the sickening odors that often leak inside their homes, residents have sealed off their chimneys, spent hundreds of dollars on air purifiers, or created makeshift filters. Others have relocated. Some people have even bought hand-held gas monitors, which have detected levels of hydrogen sulfide, a top chemical component of sewer gas, in their homes.

Concentrations of wastewater gases have been measured above the state’s nuisance odor standards in San Ysidro , according to data from a monitoring station the San Diego Air Pollution Control District began running in late September. California sets its air quality standard at 30 parts per billion (ppb), which is intended to be protective against headaches and nausea, and the U.S. Occupational Safety and Health Administration at 10 ppb.

The Air Pollution Control District is working to install more monitoring stations in South County, including in Imperial Beach, Otay Mesa West and at the South Bay International Wastewater Treatment Plant.

Vargas said the air purifiers are “an immediate, short-term measure to provide relief while broader, innovative solutions are being pursued.”

How many the county plans to offer and how people can receive them is unclear, though that should become known with the development of the program. Officials also have yet to say when they would like the effort launched.

In 2022, the county created a similar program, dubbed the Portside Air Quality Improvement and Relief Program. It offered portable air purifiers and indoor air monitoring systems to households disproportionately exposed to air pollution, such as Barrio Logan, Logan Heights and National City.

Some have criticized these programs as temporary approaches that don’t solve the root cause of the issue, in this case the failing and underfunded wastewater treatment plants that allow sewage flows to taint the Tijuana River and Pacific Ocean.

“This is an unfortunate issue that we have to deal with because this is another example of the federal government failing to address an issue that’s under their sole discretion,” said county Supervisor Jim Desmond. “This is like a band-aid on a symptom, but I think we’ve got to do something here for our residents locally.”

For many in South Bay, any aid can make a difference. Samantha Snow of Imperial Beach said the program will help many who “have to sleep with the windows closed because the smell is so strong, but also don’t have air conditioning or can’t afford to run their AC.”

“Every day we have this terrible smell, like you’re next to a porta-potty,” she said. “We have a purifier for each room, but it’s a burden to buy them and keep the filters up to date. But it’s important to have clean air.”

Tuesday’s Board of Supervisors vote came two hours after Imperial Beach Mayor Paloma Aguirre held a news conference in her city, renewing calls to Gov. Gavin Newsom to declare the issue an emergency.

The governor has acknowledged that the matter is a crisis, but has said that a state of emergency would not address the problem. Instead, he has focused on advocating for federal funds to fix and expand the South Bay wastewater plant.

Aguirre challenged Newsom’s stance.

In a Tuesday letter to him, she said the governor could provide relief under an emergency declaration, including “deploying medical staff to serve the impacted communities and cleaning up polluted state property in the Tijuana River Valley and Border Fields State Park” or he could identify the needs “of our communities to avoid preventable disease and property damage stemming from this pollution.”

Also on Tuesday, San Diego Congressional leaders announced that they introduced an amendment to the 2024 National Defense Authorization Act to establish a new federal program to combat cross-border pollution. The Tijuana River Public Health and Water Quality Restoration Program aims to improve coordination between all agencies working to address the problem and provide grants for public health and water cleanup projects.

5:42 p.m. June 4, 2024: This story was updated to include information about a new federal program.

Full coverage: The transborder sewage crisis in San Diego

County report hints at economic impact sewage crisis has on South Bay businesses. ‘It feels like we’re at a point of no return.’

June 4, 2024

County formally asks state to petition CDC to investigate cross-border sewage crisis and its impact on public health

May 22, 2024

They’re getting sick because of the cross-border sewage crisis. This committee aims to prove it.

May 18, 2024

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