Air pollution

"Bad air quality" and "Air quality" redirect here. For the obsolete medical theory, seeMiasma theory.For the measurement of air pollution, seeAir quality index.For the qualities of air, seeAtmosphere of Earth.

Air pollution from acoking oven

2016Environmental Performance Index– darker colors indicate lower concentrations offine particulate matterandnitrogen dioxide,as well as betterindoor air quality.

Deaths from air pollution per 100,000 inhabitants (IHME, 2019)

Air pollutionis the contamination of air due to the presence of substances called pollutants in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials.It is also the contamination of the indoor or outdoor environment either by chemical, physical, orbiological agentsthat alters the natural features of the atmosphere.There are many different types of air pollutants, such as gases (includingammonia,carbon monoxide,sulfur dioxide,nitrous oxides,methaneandchlorofluorocarbons),particulates(both organic and inorganic) andbiological molecules.Air pollution can cause diseases, allergies, and even death to humans; it can also cause harm to other living organisms such as animals and crops, and may damage the natural environment (for example,climate change,ozone depletionorhabitat degradation) orbuilt environment(for example,acid rain).Air pollution can be caused by both human activitiesand natural phenomena.

Air quality is closely related to theEarth's climateandecosystemsglobally. Many of the contributors of air pollution are also sources ofgreenhouse emissioni.e., burning offossil fuel.

Air pollution is a significantrisk factorfor a number ofpollution-related diseases,includingrespiratory infections,heart disease,chronic obstructive pulmonary disease(COPD),stroke,andlung cancer.Growing evidence suggests that air pollution exposure may be associated with reduced IQ scores, impaired cognition,increased risk for psychiatric disorders such asdepressionand detrimentalperinatalhealth.The human health effects of poor air quality are far reaching, but principally affect the body's respiratory system and thecardiovascular system.Individual reactions to air pollutants depend on the type of pollutant a person is exposed to,the degree of exposure, and the individual's health status andgenetics.

Air pollution is the largest environmental risk factor for disease and premature deathand the fourth largest risk factor overall for human health.Air pollution causes the premature deaths of around 7 million people worldwide each year,or a global mean loss of life expectancy (LLE) of 2.9 years,and there has been no significant change in the number of deaths caused by all forms of pollution since at least 2015.Outdoor air pollution attributable to fossil fuel use alone causes ~3.61 million deaths annually,making it oneof the top contributors to human death.Anthropogenic ozone causes around 470,000 premature deaths a year and fine particulate (PM_2.5) pollution around another 2.1 million.The scope of the air pollution crisis is large: In 2018, WHO estimated that "9 out of 10 people breathe air containing high levels of pollutants."Although the health consequences are extensive, the way the problem is handled is considered largely haphazardor neglected.

The World Bank has estimated that welfare losses (premature deaths) andproductivitylosses (lost labour) caused by air pollution cost theworld economy$5 trillion per year.The costs of air pollution are generally anexternalityto the contemporaryeconomic systemand most human activity, although they are sometimes recovered throughmonitoring, legislation, and regulation.

Many different technologies and strategies are available for reducing air pollution.Although a majority of countries haveair pollution laws,according toUNEP,43 percent of countries lack a legal definition of air pollution, 31 percent lack outdoor air quality standards, 49 percent restrict their definition to outdoor pollution only, and just 31 percent have laws for tackling pollution originating from outside their borders.National air quality laws have often been highly effective, notably the 1956Clean Air Actin Britain and theUS Clean Air Act,introduced in 1963.Some of these efforts have been successful at the international level, such as theMontreal Protocol,which reduced the release of harmfulozonedepleting chemicals, and the 1985Helsinki Protocol,which reducedsulfur emissions,while others, such asinternational action on climate change,have been less successful.

Sources of air pollution

There are many different sources of air pollution. Some air pollutants (such as nitrogen oxides) originate mainly from human activities,while some (notablyradongas) come mostly from natural sources.However, many air pollutants (including dust and sulfur dioxide) come from a mixture of natural and human sources.

Anthropogenic (human-made) sources

Demolition of the cooling towers of a power station, Athlone, Cape Town, South Africa, 2010

Controlled burningof a field outside ofStatesboro, Georgia,US, in preparation for spring planting

Smoking of fish over an open fire in Ghana, 2018

Burning ofjoss paperin aChinese templein Hong Kong

• Stationary sources include:
  • fossil-fuelpower plants andbiomasspower plants both have smoke stacks (see for exampleenvironmental impact of the coal industry)
    • Oil and gas sites that havemethane leaks
  • burning of traditional biomass such as wood, crop waste and dung. (In developing and poor countries,traditional biomass burning is the major source of air pollutants.It is also the main source of particulate pollution in many developed areas including the UK & New South Wales.Its pollutants includePAHs.)
  • manufacturing facilities (factories)
    • a 2014 study found that in China equipment-,machinery-, and devices-manufacturing and construction sectors contributed more than 50% of air pollutant emissions.This high emission is due to highemission intensityand highemission factorsin its industrial structure.
  • construction
  • renovation
  • waste incineration (incineratorsas well as open and uncontrolled fires of mismanaged waste, making up about a fourth of municipal solid terrestrial waste)
  • furnaces and other types of fuel-burning heating devices
• Mobile sourcesincludemotor vehicles,trains (particularlydiesel locomotivesandDMUs), marine vessels and aircraftas well asrocketsand re-entry of components anddebris.Theair pollution externality of carsenters the air from theexhaust gasand car tires (includingmicroplastics). Road vehicles make a significant amount of all air pollution (typically, for example, around a third to a half of all nitrogen dioxide emissions)and are a major driver ofclimate change.
• Agriculture andforest managementstrategies using controlled burns. Practices likeslash-and-burnin forests like the Amazon cause large air pollution with thedeforestation.Controlled or prescribed burning is a practice used inforest management,agriculture,prairie restoration,andgreenhouse gasreduction.Foresterscan use controlled fire as a tool because fire is a natural feature of both forest and grassland ecology.Controlled burning encourages the sprouting of some desirable forest trees, resulting in a forest renewal.

There are also sources from processes other thancombustion:

• Fumes from paint,hair spray,varnish,aerosol spraysand other solvents. These can be substantial; emissions from these sources was estimated to account for almost half of pollution fromvolatile organic compoundsin the Los Angeles basin in the 2010s.
• Waste deposition in landfills producesmethaneand open burning of waste releases harmful substances.
• Nuclear weapons,toxic gases,germ warfare,and rocketry are examples of military resources.
• Agricultural emissionsandemissions from meat production or livestockcontribute substantially to air pollution
  • Fertilized farmland may be a major source ofnitrogen oxides.

Meanacidifying emissions(air pollution) of different foods per 100g of protein

Food Types	Acidifying Emissions (g SO2eq per 100g protein)
Beef	343.6
Cheese	165.5
Pork	142.7
Lamb and mutton	139.0
Farmed crustaceans	133.1
Poultry	102.4
Farmed fish	65.9
Eggs	53.7
Groundnuts	22.6
Peas	8.5
Tofu	6.7

Natural sources

Dust storm approachingStratford, Texas,in 1935

• Dustfrom natural sources, usually large areas of land with little or no vegetation.
• Methane,emitted by thedigestionof food by animals, for examplecattle.
• Radongas fromradioactive decaywithin theEarth's crust.Radon is a colorless, odorless, naturally occurring, radioactivenoble gasthat is formed from the decay ofradium.It is considered to be a health hazard. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement and it is the second most frequent cause oflung cancer,aftercigarettesmoking.
• Smoke andcarbon monoxidefromwildfires.During periods of active wildfires, smoke from uncontrolledbiomasscombustioncan make up almost 75% of all air pollution by concentration.
• Vegetation,in some regions, emits environmentally significant amounts ofvolatile organic compounds(VOCs) on warmer days. These VOCs react with primary anthropogenic pollutants – specifically, NO_x,SO₂,andanthropogenicorganic carbon compounds – to produce a seasonal haze of secondary pollutants.Black gum,poplar, oak andwilloware some examples of vegetation that can produce abundant VOCs. The VOC production from these species result in ozone levels up to eight times higher than the low-impact tree species.
• Volcanicactivity, which producessulfur,chlorine,andashparticulates.

Emission factors

Main article:AP 42 Compilation of Air Pollutant Emission Factors

Beijingair in 2005 afterrain(left) and a smoggy day (right)

Air pollutant emission factors are reported representative values that aim to link the quantity of a pollutant released into the ambient air to an activity connected with that pollutant's release.The weight of the pollutant divided by a unit weight, volume, distance, or time of the activity generating the pollutant is how these factors are commonly stated (e.g., kilograms of particulate emitted per tonne of coal burned). These criteria make estimating emissions from diverse sources of pollution easier. Most of the time, these components are just averages of all available data of acceptable quality, and they are thought to be typical of long-term averages.

TheStockholm Convention on Persistent Organic Pollutantsidentified pesticides and otherpersistent organic pollutantsof concern. These includedioxinsandfuranswhich are unintentionally created by combustion of organics, like open burning of plastics, and areendocrine disruptorsandmutagens.

E-waste processing inAgbogbloshie,Ghana, using open-burning of electronics to access valuable metals like copper. Open burning of plastics is common in many parts of the world without the capacity for processing. Especially without proper protections, heavy metals and other contaminates canseep into the soil,and createwater pollutionand air pollution.

TheUnited States Environmental Protection Agencyhas published a compilation of air pollutant emission factors for a wide range of industrial sources.The United Kingdom, Australia, Canada, and many other countries have published similar compilations, as well as theEuropean Environment Agency.

Pollutants

Main articles:PollutantandGreenhouse gas emissions

Schematic drawing, causes and effects of air pollution: (1)greenhouse effect,(2)particulate contamination,(3) increasedUV radiation,(4)acid rain,(5) increasedground-level ozoneconcentration, (6) increased levels ofnitrogen oxides

An air pollutant is a material in the air that can have many effects on humans and the ecosystem.The substance can be solid particles, liquid droplets, or gases, and often takes the form of anaerosol(solid particles or liquid droplets dispersed and carried by a gas).A pollutant can be of natural origin or man-made. Pollutants are classified as primary or secondary. Primary pollutants are usually produced by processes such as ash from a volcanic eruption.

Other examples include carbon monoxide gas from motor vehicle exhausts or sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact.Ground level ozoneis a prominent example of a secondary pollutant. Some pollutants may be both primary and secondary: they are both emitted directly and formed from other primary pollutants.

Primary pollutants

Pollutants emitted into the atmosphere by human activity include:

• Ammonia:Emitted mainly by agricultural waste. Ammonia is a compound with the formula NH₃.It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of manypharmaceuticals.Although in wide use, ammonia is both caustic and hazardous.In the atmosphere, ammonia reacts withoxides of nitrogenand sulfur to form secondary particles.
• Carbon dioxide(CO₂): Carbon dioxide is a natural component of the atmosphere, essential for plant life and given off by the humanrespiratory system.It is potentially lethal at very high concentrations (typically 100 times "normal" atmospheric levels).Although theWorld Health Organizationrecognizes CO₂as a climate pollutant, it does not include the gas in itsAir Quality Guidelinesor set recommended targets for it.Because of its role as agreenhouse gas,CO₂has been described as "the worst climate pollutant".Statements such as this refer to its long-term atmospheric effects rather than shorter-term effects on such things as human health, food crops, and buildings. This question of terminology has practical consequences, for example, in determining whether the U.S.Clean Air Act(which is designed to improve air quality) is deemed to regulate CO₂emissions.That issue was resolved in the United States by theInflation Reduction Actof 2022, which specifically amended the Clean Air Act "to define the carbon dioxide produced by the burning offossil fuelsas an 'air pollutant.' "CO₂currently forms about 410 parts per million (ppm) of Earth's atmosphere, compared to about 280 ppm in pre-industrial times,and billions of metric tons of CO₂are emitted annually by burning of fossil fuels.CO₂increase in Earth's atmosphere has been accelerating.CO₂is anasphyxiant gasand not classified as toxic or harmful in general.Workplace exposure limits exist in places like UK (5,000 ppm for long-term exposure and 15,000 ppm for short-term exposure).Natural disasters like thelimnic eruptionatLake Nyoscan result in a sudden release of huge amount of CO₂as well.
• Carbon monoxide(CO): CO is a colorless, odorless, toxic gas.It is a product ofcombustionof fuel such as natural gas, coal or wood. Vehicular exhaust contributes to the majority of carbon monoxide let into the atmosphere. It creates a smog type formation in the air that has been linked to many lung diseases and disruptions to the natural environment and animals.
• Chlorofluorocarbons(CFCs): Emitted from goods that are now prohibited from use; harmful to the ozone layer. These are gases emitted by air conditioners, freezers, aerosol sprays, and other similar devices. CFCs reach the stratosphere after being released into the atmosphere.They interact with other gases here, causing harm to the ozone layer. UV rays are able to reach the Earth's surface as a result of this. This can result in skin cancer, eye problems, and even plant damage.
• Nitrogen oxides(NO_x): Nitrogen oxides, particularlynitrogen dioxide,are expelled from high temperature combustion, and are also produced during thunderstorms byelectric discharge.They can be seen as a brownhazedome above or aplumedownwind of cities. Nitrogen dioxide is a chemical compound with the formula NO₂.It is one of several nitrogen oxides. One of the most prominent air pollutants, this reddish-brown toxic gas has a characteristic sharp, biting odor.
• Odors: Such as from garbage, sewage, and industrial processes.
• Particulate matter/particles (PM), also known as particulates, atmospheric particulate matter (APM), or fine particles, are microscopic solid or liquid particles suspended in a gas.Aerosol is a mixture of particles and gas. Volcanoes,dust storms,forest and grassland fires, living plants, and sea spray are all sources of particles. Aerosols are produced by human activities such as the combustion of fossil fuels in automobiles, power plants, and numerous industrial processes.Averaged worldwide, anthropogenic aerosols – those made by human activities – currently account for approximately 10% of the atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease,altered lung function and lung cancer. Particulates are related to respiratory infections and can be particularly harmful to those with conditions likeasthma.
• Persistent organic pollutants,which can attach to particulates. Persistent organic pollutants are organic compounds that are resistant toenvironmental degradationdue to chemical, biological, orphotolyticprocesses (POPs). As a result, they've been discovered to survive in the environment, be capable of long-range transmission,bioaccumulatein human and animal tissue, biomagnify in food chains, and pose a major threat to human health and theecosystem.
• Persistent free radicalsconnected to airborne fine particles are linked to cardiopulmonary disease.
• Polycyclic Aromatic Hydrocarbons(PAHs): a group of aromatic compounds formed from the incomplete combustion of organic compounds including coal and oil and tobacco.
• Radioactive pollutants:Produced bynuclear explosions,nuclear events, war explosives, and natural processes such as the radioactive decay of radon.
• Sulfur oxides(SO_x): particularly sulfur dioxide, a chemical compound with the formula SO₂.SO₂is produced by volcanoes and in various industrial processes. Coal and petroleum often contain sulfur compounds, and their combustion generates sulfur dioxide. Further oxidation of SO₂,usually in the presence of a catalyst such as NO₂,forms H₂SO₄,and thusacid rainis formed. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.
• Toxic metals, such asleadandmercury,especially their compounds.
• Volatile organic compounds(VOC): VOCs are both indoor and outdoor air pollutants.They are categorized as either methane (CH₄) or non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhancedglobal warming.Other hydrocarbon VOCs are also significant greenhouse gases because of their role in creating ozone and prolonging the life ofmethane in the atmosphere.This effect varies depending on local air quality. The aromatic NMVOCs benzene, toluene and xylene are suspected carcinogens and may lead to leukemia with prolonged exposure. 1,3-butadiene is another dangerous compound often associated with industrial use.

Secondary pollutants

Secondary pollutants include:

• Ground level ozone(O₃): Ozone is created when NOx and VOCs mix. It is a significant part of the troposphere.It's also an important part of the ozone layer, which can be found in different sections of the stratosphere. Photochemical and chemical reactions involving it fuel many of the chemical activities that occur in the atmosphere during the day and night. It is a pollutant and a component ofsmogthat is produced in large quantities as a result of human activities (mostly the combustion of fossil fuels).O₃is largely produced by chemical reactions involving NO_xgases (nitrogen oxides, especially from combustion) and volatile organic compounds in the presence of sunlight. Due to the influence of temperature and sunlight on this reaction, high ozone levels are most common on hot summer afternoons.
• Peroxyacetyl nitrate(C₂H₃NO₅): similarly formed from NO_xand VOCs.
• Photochemical smog:particles are formed from gaseous primary contaminants and chemicals.Smog is a type of pollution that occurs in the atmosphere. Smog is caused by a huge volume of coal being burned in a certain region, resulting in a mixture of smoke and sulfur dioxide.Modern smog is usually caused by automotive and industrial emissions, which are acted on in the atmosphere by UV light from the sun to produce secondary pollutants, which then combine with the primary emissions to generate photochemical smog.

Other pollutants

There are many other chemicals classed as hazardous air pollutants. Some of these are regulated in the USA under theClean Air Actand in Europe under numerousdirectives(including the Air "Framework" Directive, 96/62/EC, on ambient air quality assessment and management, Directive 98/24/EC, on risks related to chemical agents at work, and Directive 2004/107/EC covering heavy metals and polycyclic aromatic hydrocarbons in ambient air).

• 
  Beforeflue-gas desulfurizationwas installed, the emissions from this power plant inNew Mexicocontained excessive amounts ofsulfur dioxide.
• 
  Thermal oxidisersare air pollution abatement options forhazardous air pollutants(HAPs),volatile organic compounds(VOCs), and odorous emissions.
• This video provides an overview of a NASA study on the human fingerprint on global air quality.

Exposure

The risk of air pollution is determined by the pollutant's hazard and the amount of exposure to that pollutant. Air pollution exposure can be measured for a person, a group, such as a neighborhood or a country's children, or an entire population. For example, one would want to determine a geographic area's exposure to a dangerous air pollution, taking into account the various microenvironments and age groups. This can be calculatedas an inhalation exposure. This would account for daily exposure in various settings, e.g. different indoor micro-environments and outdoor locations. The exposure needs to include different ages and other demographic groups, especially infants, children, pregnant women, and other sensitive subpopulations.

For each specific time that the subgroup is in the setting and engaged in particular activities, the exposure to an air pollutant must integrate the concentrations of the air pollutant with regard to the time spent in each setting and the respective inhalation rates for each subgroup, playing, cooking, reading, working, spending time in traffic, etc. A little child's inhaling rate, for example, will be lower than that of an adult. A young person engaging in strenuous exercise will have a faster rate of breathing than a child engaged in sedentary activity. The daily exposure must therefore include the amount of time spent in each micro-environmental setting as well as the kind of activities performed there. The air pollutant concentration in each microactivity/microenvironmental setting is summed to indicate the exposure.

For some pollutants such asblack carbon,traffic related exposures may dominate total exposure despite short exposure times since high concentrations coincide with proximity to major roads or participation in (motorized) traffic.A large portion of total daily exposure occurs as short peaks of high concentrations, but it remains unclear how to define peaks and determine their frequency and health impact.

In 2021, the WHO halved its recommended guideline limit for tiny particles from burning fossil fuels. The new limit fornitrogen dioxide(NO₂) is 75% lower.Growing evidence that air pollution—even when experienced at very low levels—hurts human health, led the WHO to revise its guideline (from 10 μg/m³to 5 μg/m³) for what it considers a safe level of exposure of particulate pollution, bringing most of the world—97.3 percent of the global population—into the unsafe zone.

Indoor air quality

Main articles:Indoor air qualityandIndoor air pollution in developing countries

The share of total deaths from indoor air pollution, 2017

Air quality monitoring,New Delhi, India

A lack of ventilation indoors concentrates air pollution where people often spend the majority of their time. Indoor air pollution can pose a significant health risk. According to EPA reports, the concentrations of many air pollutants can be two to five times higher in indoor air than in outdoor air. Indoor air pollutants can be up to 100 times higher in some cases than they are inside. People can spend up to 90% of their time indoors, according to the American Lung Association; the US Consumer Product Safety Commission (CPSC) 2012; and the US Environmental Protection Agency 2012a.

Indoor contaminants that can cause pollution include asbestos, biologic agents, building materials, radon, tobacco smoke, and wood stoves, gas ranges, or other heating systems.

Radon(Rn) gas, acarcinogen,is exuded from the Earth in certain locations and trapped inside houses. Building materials including carpeting andplywoodemitformaldehyde(H-CHO) gas. Paint and solvents give off volatile organic compounds (VOCs) as they dry.Leadpaint can degenerate intodustand be inhaled.

Intentional air pollution is introduced with the use ofair fresheners,incense,and other scented items. Controlled wood fires in cook stoves and fireplaces can add significant amounts of harmful smoke particulates into the air, inside and out.Indoor pollution fatalities may be caused by usingpesticidesand other chemical sprays indoors without proper ventilation. Also the kitchen in a modern produce harmful particles and gases, with equipment like toasters being one of the worst sources.

Carbon monoxide poisoning and fatalities are often caused by faulty vents and chimneys, or by the burning of charcoal indoors or in a confined space, such as a tent.Chroniccarbon monoxide poisoningcan result even from poorly-adjustedpilot lights.Traps are built into all domesticplumbingto keep sewer gas andhydrogen sulfide,out of interiors. Clothing emitstetrachloroethylene,or other dry cleaning fluids, for days after dry cleaning.

Though its use has now been banned in many countries, the extensive use ofasbestosin industrial and domestic environments in the past has left a potentially very dangerous material in many localities.Asbestosisis a chronicinflammatorymedical condition affecting the tissue of the lungs. It occurs after long-term, heavy exposure to asbestos from asbestos-containing materials in structures. Those with asbestosis have severedyspnea(shortness of breath) and are at an increased risk regarding several different types oflung cancer.As clear explanations are not always stressed in non-technical literature, care should be taken to distinguish between several forms of relevant diseases. According to the World Health Organization,these may be defined as asbestosis, lung cancer, andperitoneal mesothelioma(generally a very rare form of cancer, when more widespread it is almost always associated with prolonged exposure to asbestos).

Biological sources of air pollution are also found indoors, as gases and airborne particulates. Pets produce dander, people produce dust from minute skin flakes and decomposed hair,dust mitesin bedding, carpeting and furniture produce enzymes and micrometre-sized fecal droppings, inhabitants emit methane, mold forms on walls and generatesmycotoxinsand spores,air conditioningsystems can incubateLegionnaires' diseaseand mold, and houseplants, soil and surrounding gardens can producepollen,dust, and mold. Indoors, the lack of air circulation allows these airborne pollutants to accumulate more than they would otherwise occur in nature.

Health effects

Air pollution has both acute and chronic effects on human health, affecting a number of different systems and organs but principally affect the body's respiratory system and the cardiovascular system. Afflictions include minor to chronic upper respiratory irritation such as difficulty in breathing, wheezing, coughing,asthmaandheart disease,lung cancer,stroke,acuterespiratory infectionsin children and chronic bronchitis in adults, aggravating pre-existing heart and lung disease, or asthmatic attacks.

Short and long term exposures have been linked with premature mortality and reduced life expectancyand can result in increased medication use, increased doctor oremergency departmentvisits, more hospital admissions and premature death.Diseases that develop from persistent exposure to air pollution areenvironmental healthdiseases, which develop when a health environment is not maintained.

Even at levels lower than those considered safe by United States regulators, exposure to three components of air pollution, fine particulate matter, nitrogen dioxide and ozone, correlates with cardiac and respiratory illness.Individual reactions to air pollutants depend on the type of pollutant a person is exposed to, the degree of exposure, and the individual's health status and genetics.The most common sources of air pollution include particulates and ozone (often from burning fossil fuels),nitrogen dioxide, and sulfur dioxide. Children aged less than five years who live in developing countries are the most vulnerable population to death attributable to indoor and outdoor air pollution.

Under theClean Air Act,U.S. EPAsets limits on certain air pollutants, including setting limits on how much can be in the air anywhere in the United States.Mixed exposure to bothcarbon blackand ozone could result in significantly greater health affects.

Mortality

Estimates of the death toll from air pollution vary across publications.

Deaths caused by accidents and air pollution from fossil fuel use in power plants exceed those caused by production ofrenewable energy.

Estimated annual number of deaths attributed to air pollution in 2019. This includes three categories of air pollution: indoor household, outdoor particulate matter and ozone.

Estimates of deaths toll due to air pollution vary.In 2014 the World Health Organization estimated that every year air pollution causes the premature death of 7 million people worldwide,1 in 8 deaths worldwide.A study published in 2019 indicated that in 2015 the number may be closer to 8.8 million, with 5.5 million of these premature deaths due to air pollution from anthropogenic sources.A 2022 review concluded that in 2019 air pollution was responsible for approximately million deaths. It concluded that since 2015 little real progress against pollution has been made.Causes of deaths include strokes, heart disease,COPD,lung cancer, and lung infections.Children are particularly at risk.

In 2021, the WHO reported that outdoor air pollution was estimated to cause 4.2 million premature deaths worldwide in 2019.

The global mean loss of life expectancy (LLE; similar toYPLL) from air pollution in 2015 was 2.9 years, substantially more than, for example, 0.3 years from all forms of direct violence.Communities with persons that live beyond 85 years have low ambient air pollution, suggesting a link between air pollution levels and longevity.

Primary mechanisms

The WHO estimates that in 2016, ~58% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and stroke.The mechanisms linking air pollution to increased cardiovascular mortality are uncertain, but probably include pulmonary and systemic inflammation.

By region

India and China have the highest death rate due to air pollution.India also has more deaths from asthma than any other nation according to the World Health Organization. In 2019, 1.6 million deaths in India were caused by air pollution.In 2013, air pollution was estimated to kill 500,000 people in China each year.In 2012, 2.48% of China's total air pollution emissions were caused by exports due to US demand, causing an additional 27,963 deaths across 30 provinces.

Annual premature European deaths caused by air pollution are estimated at 430,000to 800,000.An important cause of these deaths is nitrogen dioxide and other nitrogen oxides (NOx) emitted by road vehicles.Across theEuropean Union,air pollution is estimated to reducelife expectancyby almost nine months.In a 2015 consultation document the UK government disclosed that nitrogen dioxide is responsible for 23,500 premature UK deaths per annum.There is a positive correlation betweenpneumonia-related deaths and air pollution from motor vehicle emissions in England.

Eliminating energy-related fossil fuel emissions in the United States would prevent 46,900–59,400 premature deaths each year and provide $537–$678 billion in benefits from avoided PM_2.5-related illness and death.

A study published in 2023 inSciencefocused onsulfur dioxideemissions by coal power plants (coal PM_2.5) and concluded that "exposure to coal PM_2.5was associated with 2.1 times greater mortality risk than exposure to PM_2.5from all sources. "From 1999 to 2020, a total of 460,000 deaths in the US were attributed to coal PM_2.5.

Air pollution deaths by nation due to fossil fuels

Major causes

Further information:§ Sources

A comparison of footprint-based and transboundary pollution-based relationships among G20 nations for the number of PM_2.5-related premature deaths

The largest cause of air pollution isfossil fuelcombustion– mostly the production and use ofcars,electricity production, and heating.There are estimated 4.5 million annual premature deaths worldwide due to pollutants released by high-emission power stations and vehicle exhausts.

Diesel exhaust(DE) is a major contributor to combustion-derived particulate matter air pollution. In several human experimental studies, using a well-validated exposure chamber setup, DE has been linked to acute vascular dysfunction and increased thrombus formation.

A study concluded that PM_2.5air pollutioninducedby the contemporary free trade and consumption by the19G20 nations causes two million premature deaths annually, suggesting that the average lifetime consumption of about ~28 people in these countries causes at least one premature death (average age ~67) while developing countries "cannot be expected" to implement or be able to implement countermeasures without external support or internationally coordinated efforts.

Guidelines

Main article:Air quality guideline

The US EPA has estimated that limiting ground-level ozone concentration to 65 parts per billion (ppb), would avert 1,700 to 5,100 premature deaths nationwide in 2020 compared with the 75 ppb standard. The agency projected the more protective standard would also prevent an additional 26,000 cases of aggravated asthma, and more than a million cases of missed work or school.Following this assessment, the EPA acted to protectpublic healthby lowering the National Ambient Air Quality Standards (NAAQS) for ground-level ozone to 70 ppb.

A 2008 economic study of the health impacts and associated costs of air pollution in the Los Angeles Basin and San Joaquin Valley of Southern California shows that more than 3,800 people die prematurely (approximately 14 years earlier than normal) each year because air pollution levels violate federal standards. The number of annual premature deaths is considerably higher than the fatalities related to auto collisions in the same area, which average fewer than 2,000 per year.A 2021 study found that outdoor air pollution is associated with substantiallyincreased mortality"even at low pollution levels below the current European and North American standards and WHO guideline values" shortly before the WHO adjusted its guidelines.

Cardiovascular disease

According to theGlobal Burden of Disease Study,air pollution is responsible for 19% of all cardiovascular deaths.There is strong evidence linking both short- and long-term exposure to air pollution with cardiovascular disease mortality and morbidity, stroke, blood pressure, andischemic heartdiseases (IHD).

Air pollution is a leading risk factor for stroke, particularly in developing countries where pollutant levels are highest.A systematic analysis of 17 different risk factors in 188 countries found air pollution is associated with nearly one in three strokes (29%) worldwide (33.7% of strokes in developing countries versus 10.2% in developed countries).In women, air pollution is not associated with hemorrhagic but with ischemic stroke.Air pollution was found to be associated with increased incidence and mortality from coronary stroke.Associations are believed to be causal and effects may be mediated by vasoconstriction, low-grade inflammation andatherosclerosis.Other mechanisms such as autonomic nervous system imbalance have also been suggested.

Lung disease

Research has demonstrated increased risk of developing asthmaandchronic obstructive pulmonary disease(COPD)from increased exposure to traffic-related air pollution. Air pollution has been associated with increased hospitalization and mortality from asthma and COPD.

COPD comprises a spectrum of clinical disorders that includeemphysema,bronchiectasis,andchronic bronchitis.COPD risk factors are both genetic and environmental. Elevated particle pollution contributes to the exacerbation of this disease and likely its pathogenesis.

The risk of lung disease from air pollution is greatest for infants and young children, whose normal breathing is faster than that of older children and adults; the elderly; those who work outside or spend a lot of time outside; and those who have heart or lung diseasecomorbidities.

A study conducted in 1960–1961 in the wake of theGreat Smogof 1952 compared 293 London residents with 477 residents of Gloucester, Peterborough, and Norwich, three towns with low reported death rates from chronic bronchitis. All subjects were male postal truck drivers aged 40 to 59. Compared to the subjects from the outlying towns, the London subjects exhibited more severe respiratory symptoms (including cough, phlegm, anddyspnea), reduced lung function (FEV₁and peak flow rate), and increased sputum production and purulence. The differences were more pronounced for subjects aged 50 to 59. The study controlled for age and smoking habits, so concluded that air pollution was the most likely cause of the observed differences. More studies have shown that air pollution exposure from traffic reduces lung function development in childrenand lung function may be compromised by air pollution even at low concentrations.

It is believed that, much likecystic fibrosis,serious health hazards become more apparent when living in a more urban environment. Studies have shown that in urban areas people experiencemucushypersecretion, lower levels of lung function, and more self-diagnosis of chronic bronchitis and emphysema.

Cancer (lung cancer)

Unprotected exposure to PM_2.5air pollution can be equivalent to smoking multiple cigarettes per day,potentially increasing the risk ofcancer,which is mainly the result ofenvironmental factors.

Around 300,000 lung cancer deaths were attributed globally in 2019 to exposure tofine particulate matter,PM_2.5,suspended in the air.PM_2.5exposure, such as from car exhausts, activates dormant mutations in lung cells, causing them to become cancerous.

Long-term exposure to PM_2.5(fine particulates) increases the overall risk of non-accidental mortality by 6% per 10 μg/m³increase. Exposure to PM_2.5is also associated with an increased risk of mortality fromlung cancer(range: 15–21% per 10 μg/m³increase) and total cardiovascular mortality (range: 12–14% per 10 μg/m³increase).

The review further noted that living close to busy traffic appears to be associated with elevated risks of these three outcomes – increase in lung cancer deaths, cardiovascular deaths, and overall non-accidental deaths. The reviewers also found suggestive evidence that exposure to PM_2.5is positively associated with mortality from coronary heart diseases and exposure to SO₂increases mortality from lung cancer, but the data was insufficient to provide solid conclusions.Another investigation showed that higher activity level increases deposition fraction of aerosol particles in human lung and recommended avoiding heavy activities like running in outdoor space at polluted areas.

In 2011, a large Danish epidemiological study found an increased risk of lung cancer for people who lived in areas with high nitrogen oxide concentrations.Another Danish study, likewise noted evidence of possible associations between air pollution and other forms of cancer, including cervical cancer and brain cancer.

Kidney disease

A study of 163,197 Taiwanese residents over the period of 2001–2016 estimated that every 5μg/m³decrease (from an approximate peak of 30μg/m³) in the ambient concentration of PM_2.5was associated with a 25% reduced risk ofchronic kidney diseasedevelopment.According to a cohort study involving 10,997atherosclerosispatients, higher PM 2.5 exposure is associated with increasedalbuminuria.

Fertility

Nitrogen dioxide (NO₂)

An increase in NO₂is significantly associated with a lowerlive birth ratein women undergoingIVFtreatment.In the general population, there is a significant increase inmiscarriagerate in women exposed to NO₂compared to those not exposed.

Carbon monoxide (CO)

CO exposure is significantly associated withstillbirthin the second and third trimester.

Standard line-angle structure of benzo-a-pyrene (BaP)

Polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons(PAHs) have been associated with reduced fertility. Benzo(a)pyrene (BaP) is a well-known PAH and carcinogen which is often found in exhaust fumes and cigarette smoke.PAHs have been reported to administer their toxic effects through oxidative stress by increasing the production ofReactive Oxygen Species(ROS) which can result in inflammation and cell death. More long-term exposure to PAHs can result inDNA damageand reduced repair.

Exposure to BaP has been reported to reducesperm motilityand increasing the exposure worsens this effect. Research has demonstrated that more BaPs were found in men with reported fertility issues compared to men without.

Studies have shown that BaPs can affectfolliculogenesisand ovarian development by reducing the number of ovarian germ cells via triggering cell death pathways and inducing inflammation which can lead to ovarian damage.

Particulate matter

Particulate matter (PM)refers to the collection of solids and liquids suspended in the air. These can be harmful to humans, and more research has shown that these effects may be more extensive than first thought; particularly on male fertility. PM can be different sizes, such asPM_2.5which are tiny particles of 2.5 microns in width or smaller, compared withPM₁₀which are classified as 10 microns in diameter or less.

A study in California found that increased exposure to PM_2.5led to decreased sperm motility and increased abnormal morphology. Similarly, in Poland exposure to PM_2.5and PM₁₀led to an increase in the percentage of cells with immaturechromatin(DNA that has not fully developed or has developed abnormally).

In Turkey, a study examined the fertility of men who work as toll collectors and are therefore exposed to high levels of traffic pollutants daily. Traffic pollution often has high levels of PM₁₀alongsidecarbon monoxideand nitrogen oxides.There were significant differences insperm countand motility in this study group compared to a control group with limited air pollution exposure.

In women, while overall effects on fertility do not appear significant there is an association between increased exposure to PM₁₀and early miscarriage. Exposure to smaller particulate matter, PM_2.5,appears to have an effect on conception rates in women undergoingIVFbut does not affect live birth rates.

Ozone structure showing three oxygen atoms

Ground-level ozone pollution

Ground-level ozone(O₃), when in high concentrations, is regarded as an air pollutant and is often found in smog in industrial areas.

There is limited research about the effect that ozone pollution has on fertility.At present, there is no evidence to suggest that ozone exposure poses a deleterious effect on spontaneous fertility in either females or males. However, there have been studies which suggest that high levels of ozone pollution, often a problem in the summer months, exert an effect on in vitro fertilisation (IVF) outcomes. Within an IVF population, NO_xand ozone pollutants were linked with reduced rates of live birth.

While most research on this topic is focused on the direct human exposure of air pollution, other studies have analysed the impact of air pollution on gametes and embryos within IVF laboratories. Multiple studies have reported a marked improvement inembryo quality,implantationand pregnancy rates after IVF laboratories have implemented air filters in a concerted effort to reduce levels of air pollution.Therefore, ozone pollution is considered to have a negative impact on the success ofassisted reproductive technologies(ART) when occurring at high levels.

Ozone is thought to act in a biphasic manner where a positive effect on live birth is observed when ozone exposure is limited to before IVF embryo implantation. Conversely, a negative effect is demonstrated upon exposure to ozone after embryo implantation. However, after adjusting for NO2, the association between O3 and IVF live birth rate was no longer significant.

In terms of male fertility, ozone is reported to cause a significant decrease in the concentration and count of sperm in semen after exposure.Similarly, sperm vitality, the proportion of live spermatozoa in a sample, was demonstrated to be diminished as a result of exposure to air pollution.However, findings on the effect of ozone exposure on male fertility are somewhat discordant, highlighting the need for further research.

Children

Children and infants are among the most vulnerable to air pollution. Polluted air leads to the poisoning of millions of children under the age of 15, resulting in the death of some 600,000 children annually (543,000 under 5 years of age and 52,000 aged 5-15 years).Children in low or middle income countries are exposed to higher levels of fine particulate matter than those in high income countries.

Health effects of air pollution on children include asthma, pneumonia and lower respiratory tract infections and low birth weight.A study in Europe found that exposure toultrafineparticles can increase blood pressure in children.

Prenatal exposure

Prenatal exposure to polluted air has been linked to a variety ofneurodevelopmental disordersin children. For example, exposure topolycyclic aromatic hydrocarbons(PAH) was associated with reduced IQ scores and symptoms ofanxietyanddepression.They can also lead to detrimentalperinatalhealth outcomes that are often fatal in developing countries.A 2014 study found that PAHs might play a role in the development of childhoodattention deficit hyperactivity disorder(ADHD).

Researchers have found a correlation between air pollution and risk ofautism spectrum disorder(ASD) diagnosis, although definitive causality has not yet been established. In Los Angeles, children living in areas with high levels of traffic-related air pollution were more likely to be diagnosed with autism between three–five years of age.A cohort study in Southern California linked in-utero exposure to near-roadway air pollution to an increased risk of ASD diagnosisand a study in Sweden concluded that exposure to PM_2.5during pregnancy was associated with ASD.A Danish study linked exposure to air pollution during infancy, but not during pregnancy, to an increased risk of ASD diagnosis.

The connection between air pollution and neurodevelopmental disorders in children is thought to be related to epigenetic dysregulation of the primordial germ cells, embryo, and fetus during a critical period. Some PAHs are considered endocrine disruptors and are lipid soluble. When they build up in adipose tissue they can be transferred across the placenta can exert agenotoxiceffect, cauding DNA damange and mutations.Air pollution has been associated with the prevalence of preterm births.

Infants

Ambient levels of air pollution have been associated withpreterm birthandlow birth weight.A 2014 WHO worldwide survey on maternal and perinatal health found a statistically significant association between low birth weights (LBW) and increased levels of exposure to PM_2.5.Women in regions with greater than average PM_2.5levels had statistically significant higher odds of pregnancy resulting in a low-birth weight infant even when adjusted for country-related variables.The effect is thought to be from stimulatinginflammationand increasingoxidative stress.

A study found that in 2010 exposure to PM_2.5was strongly associated with 18% of preterm births globally, which was approximately 2.7 million premature births. The countries with the highest air pollution associated preterm births were in South and East Asia, the Middle East, North Africa, and West sub-Saharan Africa.In 2019, ambient particulate matter pollution in Africa resulted in at least 383,000 early deaths, according to new estimates of the cost of air pollution in the continent. This increased from 3.6% in 1990 to around 7.4% of all premature deaths in the area.

The source of PM_2.5differs greatly by region. In South and East Asia, pregnant women are frequently exposed to indoor air pollution because of wood and otherbiomassfuels being used for cooking, which are responsible for more than 80% of regional pollution. In the Middle East, North Africa and West sub-Saharan Africa, fine PM comes from natural sources, such asdust storms.The United States had an estimated 50,000 preterm births associated with exposure to PM_2.5in 2010.

A study between 1988 and 1991 found a correlation betweensulfur dioxide(SO₂) and total suspended particulates (TSP) and preterm births and low birth weights in Beijing. A group of 74,671 pregnant women, in four separate regions of Beijing, were monitored from early pregnancy to delivery along with daily air pollution levels of SO₂and TSP (along with other particulates). The estimated reduction in birth weight was 7.3 g for every 100 μg/m³increase inSO₂and 6.9 g for each 100 μg/m³increase in TSP. These associations were statistically significant in both summer and winter, although summer was greater. The proportion of low birth weight attributable to air pollution, was 13%. This is the largest attributable risk ever reported for the known risk factors of low birth weight.Coal stoves, which are in 97% of homes, are a major source of air pollution in this area.

Brauer et al. studied the relationship between air pollution and proximity to a highway with pregnancy outcomes in a Vancouver cohort of pregnant women using addresses to estimate exposure during pregnancy. Exposure to NO, NO₂,CO, PM₁₀and PM_2.5were associated with infants born small for gestational age (SGA). Women living less than 50 meters away from an expressway or highway were 26% more likely to give birth to a SGA infant.

Central nervous system

See also:Neuroplastic effects of pollution

Data is accumulating that air pollution exposure also affects thecentral nervous system.

Air pollution increases the risk of dementia in people over 50 years old.Indoor air pollution exposure during childhood may negatively affect cognitive function and neurodevelopment.Prenatal exposuremay also affect neurodevelopment.Studies show that air pollution is associated with a variety of developmental disabilities, oxidative stress, andneuro-inflammationand that it may contribute to Alzheimer's disease and Parkinson's disease.

Researchers found that early exposure to air pollution causes the same changes in the brain asautismandschizophreniain mice. It also showed that air pollution also affectedshort-term memory,learning ability, andimpulsivity.In this study, air pollution had a larger negative impact on male mice than on females.Lead researcher on the study, Deborah Cory-Slechta, said that:

When we looked closely at theventricles,we could see that thewhite matterthat normally surrounds them hadn't fully developed. It appears thatinflammationhad damaged thosebrain cellsand prevented that region of the brain from developing, and the ventricles simply expanded to fill the space. Our findings add to the growing body of evidence that air pollution may play a role in autism, as well as in otherneurodevelopmental disorders.

Exposure to fine particulate matter can increase levels ofcytokines- neurotransmitters produced in response to infection and inflammation that are also associated with depression and suicide. Pollution has been associated with inflammation of the brain, which may disrupt mood regulation. Heightened PM_2.5levels are linked to more self-reported depressive symptoms, and increases in daily suicide rates.

In 2015, experimental studies reported the detection of significant episodic (situational) cognitive impairment from impurities in indoor air breathed by test subjects who were not informed about changes in the air quality. Significant deficits were observed in the performance scores achieved in increasing concentrations of eithervolatile organic compounds(VOCs) or carbon dioxide, while keeping other factors constant. The highest impurity levels reached are not uncommon in some classroom or office environments.Higher PM_2.5and CO₂concentrations were shown to be associated with slower response times and reduced accuracy in tests.

PM2.5 Levels Across the World's 5 Most Populated Nations in 2019

"Clean" areas

Share of the population exposed to air pollution levels above WHO guidelines, 2017

Even in areas with relatively low levels of air pollution, public health effects can be significant and costly, since a large number of people breathe in such pollutants. A study found that even in areas of the U.S. where ozone and PM_2.5meet federal standards,Medicarerecipients who are exposed to more air pollution have higher mortality rates.

Rural populations in India, like those in urban areas, are also exposed to high levels of air pollution.In 2020, scientists found that theboundary layer airover the Southern Ocean around Antarctica is 'unpolluted' by humans.

Agricultural effects

Various studies have estimated the impacts of air pollution on agriculture, especially ozone. A 2020 study showed that ozone pollution in California may reduce yields of certain perennial crops such as table grapes by as much as 22% per year, translating into economic damages of more than $1 billion per year.After air pollutants enter the agricultural environment, they not only directly affect agricultural production and quality, but also enter agricultural waters and soil.The COVID-19 induced lockdown served as a natural experiment to expose the close links between air quality and surface greenness. In India, the lockdown induced improvement in air quality, enhanced surface greenness and photosynthetic activity, with the positive response of vegetation to reduce air pollution was dominant in croplands.On the other hand, agriculture in its traditional form is one of the primary contributors to the emission of trace gases like atmospheric ammonia.

Economic effects

Air pollution costs theworld economy$5 trillion per year as a result of productivity losses and degraded quality of life.These productivity losses are caused by deaths due to diseases caused by air pollution. One out of ten deaths in 2013 was caused by diseases associated with air pollution and the problem is getting worse.

A small improvement in air quality (1% reduction of ambient PM_2.5and ozone concentrations) would produce $29 million in annual savings in the lowerFraser Valleyregion in 2010.This finding is based on health valuation of lethal (death) and sub-lethal (illness) affects.

The problem is even more acute in thedeveloping world."Children under age 5 in lower-income countries are more than 60 times as likely to die from exposure to air pollution as children in high-income countries."The report states that additional economic losses caused by air pollution, including health costsand the adverse effect on agricultural and other productivity were not calculated in the report, and thus the actual costs to the world economy are far higher than $5 trillion.

A study published in 2022 found "a strong and significant connection between air pollution and construction site accidents" and that "a 10-ppb increase in NO₂levels increases the likelihood of an accident by as much as 25% ".

Other effects

Artificial air pollution may be detectable on Earth from distant vantage points such as other planetary systems viaatmospheric SETI– including NO₂pollution levels and with telescopic technology close to today. It may also be possible to detect extraterrestrial civilizations this way.

Historical disasters

The world's worst short-term civilian pollution crisis was the 1984Bhopal Disasterin India.Leaked industrial vapours from the Union Carbide factory, belonging to Union Carbide, Inc., U.S.A. (later bought byDow Chemical Company), killed at least 3787 people and injured from 150,000 to 600,000. The United Kingdom suffered its worst air pollution event when the 4 DecemberGreat Smogof 1952 formed over London. In six days more than 4,000 died and more recent estimates put the figure at nearer 12,000.

Anaccidental leak of anthraxspores from abiological warfarelaboratory in the former USSR in 1979 near Yekaterinburg (formerly Sverdlovsk) is believed to have caused at least 64 deaths.The worst single incident of air pollution to occur in the US occurred inDonora, Pennsylvania,in late October 1948, when 20 people died and over 7,000 were injured.

Reduction and regulation

Global depletion of the surrounding air pollution will require valiant leadership, a surplus of combined resources from the international community, and extensive societal changes.Pollution prevention seeks to prevent pollution such as air pollution and could include adjustments to industrial and business activities such asdesigning sustainable manufacturing processes (and the products' designs)and related legal regulations as well as efforts towardsrenewable energy transitions.

Efforts to reduce particulate matter in the air may result in better health.

The9-Euro-Ticketscheme in Germany which allowed people to buy a monthly pass allowing use on all local and regional transport (trains, trams and busses) for 9 euro (€) for one month of unlimited travel saved 1.8 million tons of CO₂emissions during its three-month implementation from June to August 2022.

Pollution control

Burning of items polluting Jamestown environment inAccra, Ghana

Various pollution control technologies and strategies are available to reduce air pollution.At its most basic level,land-use planningis likely to involve zoning and transport infrastructure planning. In most developed countries, land-use planning is an important part of social policy, ensuring that land is used efficiently for the benefit of the wider economy and population, as well as to protect the environment.Stringent environmental regulations, effective control technologies and shift towards the renewable source of energy also helping countries like China and India to reduce their sulfur dioxide pollution.

Titanium dioxidehas been researched for its ability to reduce air pollution.Ultravioletlight will release free electrons from material, thereby creating free radicals, which break up VOCs andNO_xgases. One form issuperhydrophilic.

Pollution-eatingnanoparticlesplaced near a busy road were shown to absorb toxic emission from around 20 cars each day.

Energy transition

Since a large share of air pollution is caused by combustion of fossil fuels such as coal and oil, the reduction of these fuels can reduce air pollution drastically. Most effective is the switch to clean power sources such aswind power,solar power,hydro powerwhich do not cause air pollution.Efforts to reduce pollution from mobile sources includes expanding regulation to new sources (such as cruise and transport ships, farm equipment, and small gas-powered equipment such asstring trimmers,chainsaws,andsnowmobiles), increasedfuel efficiency(such as through the use ofhybrid vehicles), conversion to cleaner fuels, and conversion toelectric vehicles.For example, buses in New Delhi, India, have run oncompressed natural gassince 2000, to help eliminate the city's "pea-soup" smog.

A very effective means to reduce air pollution is thetransitiontorenewable energy.According to a study published inEnergy and Environmental Sciencein 2015 the switch to100% renewable energyin the United States would eliminate about 62,000 premature mortalities per year and about 42,000 in 2050, if no biomass were used. This would save about $600 billion in health costs a year due to reduced air pollution in 2050, or about 3.6% of the 2014 U.S. gross domestic product.Air quality improvement is a near-term benefit among the many societal benefits fromclimate change mitigation.

Alternatives to pollution

Support for a ban on high-emission vehicles in city centres in Europe, China and the US from respondents to the European Investment Bank Climate Survey

Support, use and infrastructure-expansion of forms ofpublic transportthat do not cause air pollution may be a critical key alternative to pollution.

There are now practical alternatives to the principal causes of air pollution:

• Strategic substitution of air pollution sources in transport with lower-emission or, during the lifecycle, emission-free forms ofpublic transportandbicycle use and infrastructure(as well as with remote work, reductions of work, relocations, andlocalizations)
  • Phase-out of fossil fuel vehiclesis a critical component of a shift tosustainable transport;however, similar infrastructure and design decisions like electric vehicles may be associated with similar pollution for production as well as mining and resource exploitation for large numbers of needed batteries as well as the energy for their recharging
• Areas downwind (over 20 miles) of major airports have more than doubletotal particulate emissions in airthan other areas, even when factoring in areas with frequent ship calls, and heavy freeway and city traffic like Los Angeles.Aviation biofuelmixed in with jetfuel at a 50/50 ratio can reduce jet derived cruise altitude particulate emissions by 50–70%, according to aNASAled 2017 study (however, this should imply ground level benefits to urban air pollution as well).
• Ship propulsion and idling can be switched to much cleaner fuels like natural gas. (Ideally arenewable sourcebut not practical yet)
• Combustion of fossil fuels for space heating can be replaced by usingground source heat pumpsandseasonal thermal energy storage.
• Electricity generated from the combustion of fossil fuels can be replaced by nuclear and renewable energy. Heating and home stoves, which contribute significantly to regional air pollution, can be replaced with a much cleaner fossil fuel, such as natural gas, or, preferably, renewables, in poor countries.
• Motor vehicles driven by fossil fuels, a key factor in urban air pollution, can be replaced by electric vehicles. Though lithium supply and cost is a limitation, there are alternatives. Herding more people into clean public transit such as electric trains can also help. Nevertheless, even in emission-free electric vehicles,rubber tires produce significant amounts of air pollutionthemselves, ranking as 13th worst pollutant in Los Angeles.
• Reducing travel in vehicles can curb pollution. After Stockholm reduced vehicle traffic in the central city with a congestion tax, nitrogen dioxide and PM₁₀pollution declined, as did acute pediatric asthma attacks.
• Biodigesterscan be utilized in poor nations whereslash and burnis prevalent, turning a useless commodity into a source of income. The plants can be gathered and sold to a central authority that will break them down in a large modern biodigester, producing much needed energy to use.
• Induced humidity and ventilation both can greatly dampen air pollution in enclosed spaces, which was found to be relatively high inside subway lines due to braking and friction and relatively less ironically inside transit buses than lower sitting passenger automobiles or subways.

Further information:§ Sources

Control devices

Tarps and netting are often used to reduce the amount of dust released fromconstruction sites.

Air pollution from a car

The following items are commonly used as pollution control devices in industry and transportation. They can either destroy contaminants or remove them from an exhaust stream before it is emitted into the atmosphere.

• Particulate control
  • Mechanical collectors (dust cyclones,multicyclones)
  • Electrostatic precipitators:An electrostatic precipitator (ESP), or electrostatic air cleaner, is a particulate collection device that removes particles from a flowing gas (such as air), using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulates such as dust and smoke from the air stream.
  • Baghouses:Designed to handle heavy dust loads, a dust collector consists of a blower, dust filter, a filter-cleaning system, and a dust receptacle or dust removal system (distinguished from air cleaners which utilize disposable filters to remove the dust).
  • Particulate scrubbers:A wet scrubber is a form of pollution control technology. The term describes a variety of devices that use pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the liquid, by forcing it through a pool of liquid, or by some other contact method, so as to remove the pollutants.
• Scrubbers
  • Baffle spray scrubber
  • Cyclonic spray scrubber
  • Ejector venturi scrubber
  • Mechanically aided scrubber
  • Spray tower
  • Wet scrubber
• NO_xcontrol
  • LO-NOx burners
  • Selective catalytic reduction(SCR)
  • Selective non-catalytic reduction(SNCR)
  • NOx scrubbers
  • Exhaust gas recirculation
  • Catalytic converter(also for VOC control)
• VOC abatement
  • Adsorption systems,usingactivated carbon,such asFluidized Bed Concentrator
  • Flares
  • Thermal oxidizers
  • Catalytic converters
  • Biofilters
  • Absorption (scrubbing)
  • Cryogeniccondensers
  • Vapor recovery systems
• Acid gas/SO₂control
  • Wet scrubbers
  • Dry scrubbers
  • Flue-gas desulfurization
• Mercurycontrol
  • Sorbent injection technology
  • Electro-catalytic oxidation (ECO)
  • K-Fuel
• Dioxinandfurancontrol
• Miscellaneous associated equipment
  • Source capturing systems
  • Continuous emissions monitoring systems(CEMS)

Monitoring

See also:Smart city

Further information:Air pollution measurementandEnvironmental monitoring

Spatiotemporalmonitoring of air quality may be necessary for improving air quality, and thereby the health and safety of the public, and assessing impacts of interventions.Such monitoring is done to different extents with different regulatory requirements with discrepant regional coverage by a variety of organizations and governance entities such as using a variety of technologies for use of the data and sensing such mobileIoTsensors,satellites,and monitoring stations.Some websites attempt to map air pollution levels using available data.

Air quality modeling

Main article:Air quality modeling

Numerical models either on a global scale using tools such as GCMs (general circulation modelscoupled with a pollution module) or CTMs (Chemical transport model) can be used to simulate the levels of different pollutants in the atmosphere. These tools can have several types (Atmospheric model) and different uses. These models can be used in forecast mode which can help policy makers to decide on appropriate actions when an air pollution episode is detected. They can also be used for climate modeling including evolution of air quality in the future, for example the IPCC (Intergovernmental Panel on Climate Change) provides climate simulations including air quality assessments in their reports (latest report accessible through theirsite).

Regulations

Main article:Air quality law

Smog inCairo

In general, there are two types of air quality standards. The first class of standards (such as the U.S.National Ambient Air Quality Standardsand E.U. Air Quality Directive) set maximum atmospheric concentrations for specific pollutants. Environmental agencies enact regulations which are intended to result in attainment of these target levels. The second class (such as the North Americanair quality index) take the form of a scale with various thresholds, which is used to communicate to the public the relative risk of outdoor activity. The scale may or may not distinguish between different pollutants.

Canada

In Canada, air pollution and associated health risks are measured with theAir Quality Health Index(AQHI).It is a health protection tool used to make decisions to reduce short-term exposure to air pollution by adjusting activity levels during increased levels of air pollution.

The AQHI is a federal program jointly coordinated byHealth CanadaandEnvironment Canada.However, the AQHI program would not be possible without the commitment and support of the provinces, municipalities andNGOs.From air quality monitoring to healthrisk communicationand community engagement, local partners are responsible for the vast majority of work related to AQHI implementation. The AQHI provides a number from 1 to 10+ to indicate the level of health risk associated with local air quality. Occasionally, when the amount of air pollution is abnormally high, the number may exceed 10. The AQHI provides a local air quality current value as well as a local air quality maximums forecast for today, tonight and tomorrow and provides associated health advice.

1

2

3

4

5

6

7

8

9

10

+

Risk:

Low(1–3)

Moderate(4–6)

High(7–10)

Very high(above 10)

As it is now known that even low levels of air pollution can trigger discomfort for the sensitive population, the index has been developed as a continuum: The higher the number, the greater the health risk and need to take precautions. The index describes the level of health risk associated with this number as 'low', 'moderate', 'high' or 'very high', and suggests steps that can be taken to reduce exposure.

Health risk	Air Quality Health Index	Health messages
		At risk population	General population
Low	1–3	Enjoyyour usual outdoor activities.	Idealair quality for outdoor activities
Moderate	4–6	Consider reducingor rescheduling strenuous activities outdoors if you are experiencing symptoms.	No need to modifyyour usual outdoor activities unless you experience symptoms such as coughing and throat irritation.
High	7–10	Reduceor reschedule strenuous activities outdoors. Children and the elderly should also take it easy.	Consider reducingor rescheduling strenuous activities outdoors if you experience symptoms such as coughing and throat irritation.
Very high	Above 10	Avoidstrenuous activities outdoors.Childrenand theelderlyshould also avoid outdoor physical exertion and should stay indoors.	Reduceor reschedule strenuous activities outdoors, especially if you experience symptoms such as coughing and throat irritation.

The measurement is based on the observed relationship ofnitrogen dioxide(NO₂), ground-level ozone (O₃) and particulates (PM_2.5) with mortality, from an analysis of several Canadian cities. Significantly, all three of these pollutants can pose health risks, even at low levels of exposure, especially among those with pre-existing health problems.

When developing the AQHI, Health Canada's original analysis of health effects included five major air pollutants: particulates,ozone,andnitrogen dioxide(NO₂), as well assulfur dioxide(SO₂), andcarbon monoxide(CO). The latter two pollutants provided little information in predicting health effects and were removed from the AQHI formulation.

The AQHI does not measure the effects of odour, pollen, dust, heat or humidity.

Germany

TA Luftis the German air quality regulation.

Governing urban air pollution

Further information:Phase-out of fossil fuel vehicles § Cities and territories

In Europe, Council Directive 96/62/EC on ambient air quality assessment and management provides a common strategy against whichmember statescan "set objectives for ambient air quality in order to avoid, prevent or reduce harmful effects on human health and the environment... and improve air quality where it is unsatisfactory".

In July 2008, in the caseDieter Janecek v. Freistaat Bayern,theEuropean Court of Justiceruled that under this directivecitizens have the right to require national authorities to implement a short term action plan that aims to maintain or achieve compliance to air quality limit values.

This important case law appears to confirm the role of the EC as centralised regulator to European nation-states as regards air pollution control. It places asupranationallegal obligation on the UK to protect its citizens from dangerous levels of air pollution, furthermore superseding national interests with those of the citizen.

In 2010, theEuropean Commission(EC) threatened the UK with legal action against the successive breaching ofPM₁₀limit values.The UK government has identified that if fines are imposed, they could cost the nation upwards of £300 million per year.

In March 2011, the Greater London Built-up Area remained the only UK region in breach of the EC's limit values, and was given three months to implement an emergency action plan aimed at meeting the EU Air Quality Directive.The City of London has dangerous levels of PM₁₀concentrations, estimated to cause 3000 deaths per year within the city.As well as the threat of EU fines, in 2010 it was threatened with legal action for scrapping the westerncongestion chargezone, which is claimed to have led to an increase in air pollution levels.

In response to these charges, mayor of LondonBoris Johnsonhas criticised the current need for European cities to communicate with Europe through their nation state'scentral government,arguing that in future "A great city like London" should be permitted to bypass its government and deal directly with the European Commission regarding its air quality action plan.

This can be interpreted as recognition that cities can transcend the traditional national government organisational hierarchy and develop solutions to air pollution using global governance networks, for example through transnational relations. Transnational relations include but are not exclusive to national governments and intergovernmental organisations,allowing sub-national actors including cities and regions to partake in air pollution control as independent actors.

Global city partnerships can be built into networks, for example theC40 Cities Climate Leadership Group,of which London is a member. The C40 is a public 'non-state' network of the world's leading cities that aims to curb their greenhouse emissions.The C40 has been identified as 'governance from the middle' and is an alternative to intergovernmental policy.It has the potential to improve urban air quality as participating cities "exchange information, learn from best practices and consequently mitigate carbon dioxide emissions independently from national government decisions".A criticism of the C40 network is that its exclusive nature limits influence to participating cities and risks drawing resources away from less powerful city and regional actors.

Indigenous people

Because Indigenous peoplefrequently experience a disproportionate share of the effects of environmental degradation and climate change, even while they have made very little contribution to the processes causing these changes, environmental justice is especially important to them. Indigenous peoples have been marginalized and their lands and resources have been exploited as a result of historical and continuing colonization, institutional injustices, and inequality.

Indigenous groups frequently lack the political and financial clout to influence policy decisions that impact their lands and means of subsistence or to lessen the effects of climate change. This makes the already-existing inequalities in these communities' social, economic, and health conditions worse. Furthermore, traditional ecological knowledge and Indigenous knowledge systems provide insightful information about sustainable resource management and climate change adaptation techniques. To promote persistence and environmental justice, Indigenous viewpoints must be acknowledged and integrated into efforts to mitigate the effects of climate change and adapt to them.

Combating climate change necessitates an all-encompassing strategy that recognizes the interdependence of social, economic, and environmental elements. This entails defending treaty rights, advancing Indigenous sovereignty and self-determination, and aiding Indigenous-led projects for sustainable development and environmental preservation.

Hotspots

Main article:Toxic hotspot

See also:Cancer alleyandSuperfund

Air pollution hotspots are areas where air pollution emissions expose individuals to increased negative health effects.They are particularly common in highly populated, urban areas, where there may be a combination of stationary sources (e.g. industrial facilities) and mobile sources (e.g. cars and trucks) of pollution. Emissions from these sources can causerespiratory disease,childhoodasthma,cancer,and other health problems. Fine particulate matter such asdiesel soot,which contributes to more than 3.2 million premature deaths around the world each year, is a significant problem. It is very small and can lodge itself within the lungs and enter the bloodstream. Diesel soot is concentrated in densely populated areas, and one in six people in the U.S. live near a diesel pollution hot spot.

External videos
AirVisual Earth– realtime map of global wind and air pollution

While air pollution hotspots affect a variety of populations, some groups are more likely to be located in hotspots. Previous studies have shown disparities in exposure to pollution by race and/or income.Hazardousland uses (toxic storage and disposal facilities, manufacturing facilities, major roadways) tend to be located where property values and income levels are low. Lowsocioeconomicstatus can be a proxy for other kinds ofsocial vulnerability,including race, a lack of ability to influence regulation and a lack of ability to move to neighborhoods with less environmental pollution. These communities bear a disproportionate burden of environmental pollution and are more likely to face health risks such ascancerorasthma.

Studies show that patterns in race and income disparities not only indicate a higher exposure to pollution but also higher risk of adverse health outcomes.Communities characterized by lowsocioeconomicstatus and racial minorities can be more vulnerable to cumulative adverse health impacts resulting from elevated exposure to pollutants than more privileged communities.Blacks and Latinos generally face more pollution than Whites and Asians, and low-income communities bear a higher burden of risk than affluent ones.Racial discrepancies are particularly distinct in suburban areas of the Southern United States and metropolitan areas of the Midwestern and Western United States.Residents in public housing, who are generally low-income and cannot move to healthier neighborhoods, are highly affected by nearbyrefineriesand chemical plants.

Cities

See also:List of most polluted cities in the world by particulate matter concentration

Further information:List of least polluted cities by particulate matter concentration

Nitrogen dioxide concentrations as measured from satellite 2002–2004

Air pollution is usually concentrated in densely populatedmetropolitan areas,especially in developing countries where cities are experiencing rapid growth and environmental regulations are relatively lax or nonexistent. Urbanization leads to a rapid rise in prematuremortalitydue to anthropogenic air pollution in fast-growing tropical cities.However, even populated areas in developed countries attain unhealthy levels of pollution, with Los Angeles and Rome being two examples.Between 2002 and 2011 the incidence of lung cancer in Beijing near doubled. While smoking remains the leading cause of lung cancer in China, the number of smokers is falling while lung cancer rates are rising.

World's Most Polluted Cities 2020	2020 Average	2019 Average
Hotan, China	110.2	110.1
Ghaziabad, India	106.6	110.2
Bulandshahr, India	98.4	89.4
Bisrakh Jalalpur, India	96.0	-
Bhiwadi, India	95.5	83.4

Tehran was declared the most polluted city in the world on May 24, 2022.

Projections

In a 2019 projection, by 2030 half of the world's pollution emissions could be generated by Africa.Potential contributors to such an outcome include increased burning activities (such as the burning of open waste), traffic, agri-food and chemical industries, sand dust from the Sahara, and overallpopulation growth.

In a 2012 study, by 2050 outdoor air pollution (particulate matter and ground-level ozone) is projected to become the top cause of environmentally related deaths worldwide.

See also

Source

• Beehive burner
• Bottom ash
• Concrete#Concrete – health and safety
• Diwali-related air pollution
• Flue-gas emissions from fossil-fuel combustion
• Health impacts of sawdust
• Joss paper
• Metal working
• Mining
• Non-exhaust emissions
• Power tool
• Rubber pollution
• Slag
• Smelting
• Tire fire
• Welding
• Wood ash

Measurement

• Air pollutant concentrations
• Air pollution measurement
• Organic molecular tracers
• Intake fraction
• Particulate matter sampler

Others

• Air stagnation
• ASEAN Agreement on Transboundary Haze Pollution
• Asian brown cloud
• Atmospheric chemistry
• BenMAP
• Best Available Control Technology
• Critical load
• Emission standard
• Emissions & Generation Resource Integrated Database
• Environmental agreement
• Environmental racism
• Exposome
• Global Atmosphere Watch
• Global dimming
• Great Smogof London
• Haze
• Health Effects Institute(HEI)
• Indicator value
• International Agency for Research on Cancer
• International Day of Clean Air for Blue Skies
• Kyoto Protocol
• Light water reactor sustainability
• List of smogs by death toll
• Lowest Achievable Emissions Rate
• NASA Clean Air Study
• NIEHS
• Phytoremediation
• Polluter pays principle
• Regulation of greenhouse gases under the Clean Air Act
• Silicosis#Prevention

Further reading

• Brimblecombe P(1987).The Big Smoke: A History of Air Pollution in London Since Medieval Times.Routledge.ISBN978-1-136-70329-4.
• Brimblecombe P(1995). "1: History of air pollution". In Singh H (ed.).Composition, chemistry, and climate of the atmosphere.New York: John Wiley & Sons. pp. 1–18.ISBN978-0-471-28514-4.OCLC43084000.
• Brimblecombe P,Makra L(2005). "Selections from the history of environmental pollution, with special attention to air pollution. Part 2*: From medieval times to the 19th century".International Journal of Environment and Pollution.23(4): 351–67.doi:10.1504/ijep.2005.007599.
• Cherni, Judith A.Economic Growth versus the Environment: The Politics of Wealth, Health and Air Pollution(2002)online
• Corton, Christine L.London Fog: The Biography(2015)
• Currie, Donya. "WHO: Air Pollution a Continuing Health Threat in World's Cities",The Nation's Health(February 2012) 42#1online
• Dewey, Scott Hamilton.Don't Breathe the Air: Air Pollution and US Environmental Politics, 1945–1970(Texas A & M University Press, 2000)
• Gonzalez, George A.The politics of air pollution: Urban growth, ecological modernization, and symbolic inclusion(SUNY Press, 2012)
• Grinder RD (1978). "From Insurgency to Efficiency: The Smoke Abatement Campaign in Pittsburgh before World War I.".Western Pennsylvania Historical Magazine.61(3): 187–202.
• Grinder, Robert Dale. "The Battle for Clean Air: The Smoke Problem in Post-Civil War America" in Martin V. Melosi, ed.,Pollution & Reform in American Cities, 1870–1930(1980), pp. 83–103.
• Kumar P, Pirjola L, Ketzel M, Harrison RM (2013)."Nanoparticle emissions from 11 non-vehicle exhaust sources – A review".Atmospheric Environment.67.Elsevier BV: 252–277.Bibcode:2013AtmEn..67..252K.doi:10.1016/j.atmosenv.2012.11.011.ISSN1352-2310.
• Lundqvist LJ (1980).The Hare and the Tortoise: Clean Air Policy in the US and Sweden.Ann Arbor, MI: University of Michigan Press.ISBN978-0-472-09310-6.
• Mingle, Jonathan, "Our Lethal Air" [review of Gary Fuller,The Invisible Killer...;Beth Gardiner,Choked...;Tim Smedley,Clearing the Air...;U.S. Environmental Protection Agency,Integrated Science Assessment forParticulate Matter(External Review Draft, 2018);and Chartered Clean Air Scientific Advisory Committee,Letter to EPA Administrator on the EPA's Integrated Science Assessment for Particulate Matter, 11 April 2019],The New York Review of Books,vol. LXVI, no. 14 (26 September 2019), pp. 64–66, 68. "Today, 91 percent of people worldwide live in areas where air pollution levels exceed the World Health Organization's recommended limits.... [T]here is no safe level of exposure to fineparticulate matter.... Most of these fine particles are a by-product of... burning...coal,gasoline,diesel,wood,trash... These particles can get past the defenses of ourupper airwaysto penetrate deep into ourlungsand reach thealveoli... From there, they cross into thebloodstreamand spread throughout the body. They can travel through thenose,up theolfactory nerve,and lodge... in thebrain.They can form deposits on the lining ofarteries,constrictingblood vesselsand raising the likelihood of...strokesandheart attacks.[T]hey exacerbate respiratory illnesses likeasthmaandchronic obstructive pulmonary disease... There's... evidence linking air pollution exposure to an increased risk ofAlzheimer'sand other forms ofdementia."(p. 64.)
• Mosley, Stephen. The chimney of the world: a history of smoke pollution in Victorian and Edwardian Manchester. Routledge, 2013.
• Schreurs, Miranda A.Environmental Politics in Japan, Germany, and the United States(Cambridge University Press, 2002)online
• Thorsheim, Peter.Inventing Pollution: Coal, Smoke, and Culture in Britain since 1800(2009)

External links

• WHO fact sheet on outdoor air pollution
• Air Pollution: Everything You Need to KnowGuide by the Natural Resources Defense Council (NRDC)
• Global real-time air quality index map
• Air Quality Index (AQI) Basics
• AQI CalculatorAQI to Concentration and Concentration to AQI for five pollutants
• UNEP Urban environmental planning
• European Commission > Environment > Air > Air Quality
• Database: outdoor air pollution in citiesfrom the World Health Organization
• The Mortality Effects of Long-Term Exposure to Particulate Air Pollution in the United Kingdom,UK Committee on the Medical Effects of Air Pollution, 2010.
• Hazardous air pollutants|What are hazardous pollutantsat EPA.gov