Our+Investigation

=Air pollution=

From Wikipedia, the free encyclopedia
Jump to: [|navigation], [|search] The atmosphere is a complex, dynamic natural gaseous system that is essential to support life on planet [|Earth]. [|Stratospheric] [|ozone depletion] due to air pollution has long been recognized as a threat to human health as well as to the Earth's [|ecosystems].  Air pollution from [|World War II] production. hide] * [|1] [|Pollutants] 
 * Air pollution** is the introduction of [|chemicals], [|particulate matter], or [|biological materials] that cause harm or discomfort to humans or other living organisms, or damages the [|natural environment], into the [|atmosphere].
 * ==Contents==
 * [|2] [|Sources]
 * [|2.1] [|Emission factors]
 * [|3] [|Indoor air quality (IAQ)]
 * [|4] [|Health effects]
 * [|4.1] [|Effects on cystic fibrosis]
 * [|4.2] [|Effects on COPD]
 * [|4.3] [|The Great Smog of 1952]
 * [|4.4] [|Effects on children]
 * [|4.5] [|Health effects in relatively "clean" areas]
 * [|5] [|Reduction efforts]
 * [|5.1] [|Control devices]
 * [|6] [|Legal regulations]
 * [|6.1] [|Canada]
 * [|6.2] [|European Union]
 * [|6.2.1] [|United Kingdom]
 * [|6.3] [|United States]
 * [|7] [|Statistics]
 * [|7.1] [|Most polluted cities]
 * [|7.2] [|Carbon dioxide emissions]
 * [|8] [|Atmospheric dispersion]
 * [|9] [|Environmental impacts of greenhouse gas pollutants]
 * [|10] [|See also]
 * [|11] [|References]
 * [|12] [|External links] ||

[[|edit]] Pollutants
Main article: [|Pollutant] Before [|flue gas desulfurization] was installed, the emissions from this power plant in [|New Mexico] contained excessive amounts of [|sulfur dioxide]. An air pollutant is known as a substance in the air that can cause harm to humans and the environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man-made.[|[1]] Pollutants can be classified as either primary or secondary. Usually, primary pollutants are substances directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone - one of the many secondary pollutants that make up photochemical smog. Note that some pollutants may be both primary and secondary: that is, they are both emitted directly and formed from other primary pollutants. About 4 percent of deaths in the United States can be attributed to air pollution, according to the Environmental Science Engineering Program at the Harvard School of Public Health. Major primary pollutants produced by human activity include: Secondary pollutants include: Minor air pollutants include: Persistent organic pollutants (POPs) are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. Because of this, they have been observed to persist in the environment, to be capable of long-range transport, bioaccumulate in human and animal tissue, biomagnify in food chains, and to have potential significant impacts on human health and the environment. 
 * [|Sulfur oxides] (SOx) - especially sulfur dioxide, a chemical compound with the formula SO2. SO2 is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain.[2] This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.
 * [|Nitrogen oxides] (NOx) - especially [|nitrogen dioxide] are emitted from high temperature combustion. Can be seen as the brown haze dome above or [|plume] downwind of cities.Nitrogen dioxide is the chemical compound with the formula NO2. It is one of the several nitrogen oxides. This reddish-brown toxic gas has a characteristic sharp, biting odor. NO2 is one of the most prominent air pollutants.
 * [|Carbon monoxide] - is a colourless, odourless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.
 * [|Carbon dioxide] (CO2) - a [|greenhouse gas] emitted from combustion but is also a gas vital to [|living organisms]. It is a natural gas in the atmosphere.
 * [|Volatile organic compounds] - VOCs are an important outdoor air pollutant. In this field they are often divided into the separate categories of methane (CH4) and non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced global warming. Other hydrocarbon VOCs are also significant greenhouse gases via their role in creating ozone and in prolonging the life of methane in the atmosphere, although the effect varies depending on local air quality. Within the NMVOCs, the aromatic compounds benzene, toluene and xylene are suspected carcinogens and may lead to leukemia through prolonged exposure. 1,3-butadiene is another dangerous compound which is often associated with industrial uses.
 * [|Particulate matter] - Particulates, alternatively referred to as particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to particles and the gas together. Sources of particulate matter can be man made or natural. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols. Averaged over the globe, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of the total amount of aerosols in our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer.
 * Toxic [|metals], such as [|lead], [|cadmium] and [|copper].
 * [|Chlorofluorocarbons] (CFCs) - harmful to the [|ozone layer] emitted from products currently banned from use.
 * [|Ammonia] (NH3) - emitted from agricultural processes. 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 many pharmaceuticals. Although in wide use, ammonia is both caustic and hazardous.
 * [|Odors] - such as from garbage, sewage, and industrial processes
 * [|Radioactive pollutants] - produced by [|nuclear explosions], war [|explosives], and natural processes such as the [|radioactive decay] of [|radon].
 * Particulate matter formed from gaseous primary pollutants and compounds in photochemical smog .Smog is a kind of air pollution; the word "smog" is a portmanteau of smoke and fog. Classic smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. Modern smog does not usually come from coal but from vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.
 * [|Ground level ozone] (O3) formed from NOx and VOCs. Ozone (O3) is a key constituent of the troposphere (it is also an important constituent of certain regions of the stratosphere commonly known as the Ozone layer). Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night. At abnormally high concentrations brought about by human activities (largely the combustion of fossil fuel), it is a pollutant, and a constituent of smog.
 * [|Peroxyacetyl nitrate] (PAN) - similarly formed from NOx and VOCs.
 * A large number of minor [|hazardous air pollutants]. Some of these are regulated in USA under the [|Clean Air Act] and in Europe under the Air Framework Directive.
 * A variety of [|persistent organic pollutants], which can attach to particulate matter.

[[|edit]] Sources
Main article: [|AP 42 Compilation of Air Pollutant Emission Factors] Dust storm approaching [|Stratford, Texas] [|Controlled burning] of a field outside of [|Statesboro, Georgia] in preparation for spring planting [|Aerial photo] of Los Angeles Sources of air pollution refer to the various locations, activities or factors which are responsible for the releasing of pollutants in the atmosphere. These sources can be classified into two major categories which are: 
 * Anthropogenic sources** (human activity) mostly related to burning different kinds of [|fuel]
 * "Stationary Sources" include smoke stacks of [|power plants], manufacturing facilities (factories) and waste incinerators, as well as furnaces and other types of fuel-burning heating devices
 * "Mobile Sources" include [|motor vehicles], marine vessels, aircraft and the effect of sound etc.
 * [|Chemicals], dust and [|controlled burn] practices in agriculture and forestry management. Controlled or prescribed burning is a technique sometimes used in forest management, farming, prairie restoration or greenhouse gas abatement. Fire is a natural part of both forest and grassland ecology and controlled fire can be a tool for foresters. Controlled burning stimulates the germination of some desirable forest trees, thus renewing the forest.
 * Fumes from [|paint], [|hair spray], [|varnish], [|aerosol sprays] and other solvents
 * Waste deposition in [|landfills], which generate [|methane].Methane is not toxic; however, it is highly flammable and may form explosive mixtures with air. Methane is also an asphyxiant and may displace oxygen in an enclosed space. Asphyxia or suffocation may result if the oxygen concentration is reduced to below 19.5% by displacement
 * Military, such as [|nuclear weapons], [|toxic gases], [|germ warfare] and [|rocketry]
 * Natural sources**
 * [|Dust] from natural sources, usually large areas of land with little or no vegetation.
 * [|Methane], [|emitted] by the [|digestion] of food by [|animals], for example [|cattle].
 * [|Radon] gas from radioactive decay within the Earth's crust.Radon is a colorless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium. 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 of lung cancer, after cigarette smoking.
 * [|Smoke] and [|carbon monoxide] from [|wildfires].
 * [|Volcanic] activity, which produce [|sulfur], [|chlorine], and ash [|particulates].

[[|edit]] Emission factors
Main article: [|AP 42 Compilation of Air Pollutant Emission Factors] Air [|pollutant] emission factors are representative values that attempt to relate the quantity of a pollutant released to the ambient air with an activity associated with the release of that pollutant. These factors are usually expressed as the weight of pollutant divided by a unit weight, volume, distance, or duration of the activity emitting the pollutant (e.g., kilograms of particulate emitted per megagram of coal burned). Such factors facilitate estimation of emissions from various sources of air pollution. In most cases, these factors are simply averages of all available data of acceptable quality, and are generally assumed to be representative of long-term averages. The [|United States Environmental Protection Agency] has published a compilation of air pollutant emission factors for a multitude of industrial sources.[|[2]] The [|United Kingdom], [|Australia], [|Canada] and other countries have published similar compilations, as has the [|European Environment Agency].[|[3]][|[4]][|[5]][|[6]][|[7]] 

[[|edit]] Indoor air quality (IAQ)
Main article: [|Indoor air quality] A lack of ventilation indoors concentrates air pollution where people often spend the majority of their time. Radon (Rn) gas, a [|carcinogen], is exuded from the Earth in certain locations and trapped inside houses. Building materials including [|carpeting] and [|plywood] emit [|formaldehyde] (H2CO) gas. Paint and solvents give off [|volatile organic compounds] (VOCs) as they dry. [|Lead] paint can degenerate into [|dust] and be inhaled. Intentional air pollution is introduced with the use of [|air fresheners], [|incense], and other scented items. Controlled wood fires in stoves and [|fireplaces] can add significant amounts of smoke particulates into the air, inside and out[|[8]]. Indoor pollution fatalities may be caused by using [|pesticides] and other chemical sprays indoors without proper ventilation. Carbon monoxide (CO) poisoning and fatalities are often caused by faulty vents and chimneys, or by the burning of [|charcoal] indoors. Chronic carbon monoxide poisoning can result even from poorly adjusted [|pilot lights]. Traps are built into all domestic [|plumbing] to keep sewer gas, [|hydrogen sulfide], out of interiors. Clothing emits [|tetrachloroethylene], or other dry cleaning fluids, for days after [|dry cleaning]. Though its use has now been banned in many countries, the extensive use of [|asbestos] in industrial and domestic environments in the past has left a potentially very dangerous material in many localities. [|Asbestosis] is a chronic [|inflammatory] medical condition affecting the tissue of the [|lungs]. It occurs after long-term, heavy exposure to asbestos from asbestos-containing materials in structures. Sufferers have severe [|dyspnea] (shortness of breath) and are at an increased risk regarding several different types of [|lung 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 Organisation (WHO)], these may defined as; [|asbestosis], //lung cancer//, and //[|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 [|mites] in bedding, carpeting and furniture produce enzymes and micrometre-sized fecal droppings, inhabitants emit methane, [|mold] forms in walls and generates [|mycotoxins] and spores, [|air conditioning] systems can incubate [|Legionnaires' disease] and mold, and [|houseplants], soil and surrounding [|gardens] can produce [|pollen], dust, and mold. Indoors, the lack of air circulation allows these airborne pollutants to accumulate more than they would otherwise occur in nature. 

[[|edit]] Health effects
The World Health Organization states that 2.4 million people die each year from causes directly attributable to air pollution, with 1.5 million of these deaths attributable to indoor air pollution.[|[9]] "[|Epidemiological] studies suggest that more than 500,000 Americans die each year from [|cardiopulmonary] disease linked to breathing [|fine particle air pollution]. . ."[|[10]] A study by the [|University of Birmingham] has shown a strong correlation between [|pneumonia] related deaths and air pollution from motor vehicles.[|[11]] Worldwide more deaths per year are linked to air pollution than to automobile accidents.[//[|citation needed]//] Published in 2005 suggests that 310,000 Europeans die from air pollution annually.[//[|citation needed]//] Direct causes of air pollution related deaths include aggravated asthma, bronchitis, emphysema, lung and heart diseases, and respiratory allergies.[//[|citation needed]//] The [|US EPA] estimates that a proposed set of changes in [|diesel] engine technology (//Tier 2//) could result in 12,000 fewer //premature mortalities//, 15,000 fewer [|heart attacks], 6,000 fewer [|emergency room] visits by children with [|asthma], and 8,900 fewer respiratory-related hospital admissions each year in the United States.[//[|citation needed]//] The worst short term civilian pollution crisis in [|India] was the 1984 [|Bhopal Disaster].[|[12]] Leaked industrial vapors from the Union Carbide factory, belonging to Union Carbide, Inc., U.S.A., killed more than 2,000 people outright and injured anywhere from 150,000 to 600,000 others, some 6,000 of whom would later die from their injuries.[//[|citation needed]//] The United Kingdom suffered its worst air pollution event when the [|December 4] [|Great Smog of 1952] formed over [|London]. In six days more than 4,000 died, and 8,000 more died within the following months.[//[|citation needed]//] An accidental leak of [|anthrax] spores from a [|biological warfare] laboratory in the former [|USSR] in 1979 near [|Sverdlovsk] is believed to have been the cause of hundreds of civilian deaths.[//[|citation needed]//] The worst single incident of air pollution to occur in the [|United States of America] occurred in [|Donora, Pennsylvania] in late October, 1948, when 20 people died and over 7,000 were injured.[|[13]] The health effects caused by air pollutants may range from subtle biochemical and physiological changes to difficulty in breathing, wheezing, coughing and aggravation of existing respiratory and cardiac conditions. These effects can result in increased medication use, increased doctor or emergency room visits, more hospital admissions and premature death. The human health effects of poor air quality are far reaching, but principally affect the body's respiratory system and the cardiovascular system. Individual reactions to air pollutants depend on the type of pollutant a person is exposed to, the degree of exposure, the individual's health status and genetics.[//[|citation needed]//] A new 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 3800 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 [|[14]]. 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.[|[15]][|[16]] This serves as a plausible mechanistic link between the previously described association between particulate matter air pollution and increased cardiovascular morbidity and mortality. 

[[|edit]] Effects on cystic fibrosis
Main article: [|Cystic fibrosis] A study from 1999 to 2000 by the [|University of Washington] showed that patients near and around particulate matter air pollution had an increased risk of pulmonary exacerbations and decrease in lung function.[|[17]] Patients were examined before the study for amounts of specific pollutants like //[|Pseudomonas aeruginosa]// or //[|Burkholderia cenocepacia]// as well as their socioeconomic standing. Participants involved in the study were located in the United States in close proximity to an [|Environmental Protection Agency].[//[|clarification needed]//] During the time of the study 117 deaths were associated with air pollution. A trend was noticed that patients living closer or in large metropolitan areas to be close to medical help also had higher level of pollutants found in their system because of more emissions in larger cities. With cystic fibrosis patients already being born with decreased lung function everyday pollutants such as smoke emissions from automobiles, tobacco smoke and improper use of indoor heating devices could add to the disintegration of lung function.[|[18]] 

[[|edit]] Effects on COPD
Main article: [|COPD] [|Chronic obstructive pulmonary disease] (COPD) include diseases such as [|chronic bronchitis], [|emphysema], and some forms of asthma.[|[19]] A study conducted in 1960-1961 in the wake of the [|Great Smog of 1952] compared 293 London residents with 477 from towns reporting low death rates from chronic bronchitis (Gloucester, Peterborough, and Norwich). All subjects were male postal workers aged 40 to 59. Compared to the subjects from the outlying towns, the London subjects exhibited more severe respiratory symptoms (including cough, phlegm, and dyspnea), reduced lung function (FEV1 and 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, and so concluded that local air pollution was the most likely cause of the observed differences.[|[20]] It is believed that much like [|cystic fibrosis], by living in a more urban environment serious health hazards become more apparent. Studies have shown that in urban areas patients suffer [|mucus] hypersecretion, lower levels of lung function, and more self diagnosis of chronic bronchitis and emphysema.[|[21]] 

[[|edit]] The Great Smog of 1952
Main article: [|Great Smog of 1952] Early in December 1952, a cold fog descended upon London. Because of the cold, Londoners began to burn more coal than usual. The resulting air pollution was trapped by the inversion layer formed by the dense mass of cold air. Concentrations of pollutants, coal smoke in particular, built up dramatically. The problem was made worse by use of low-quality, high-sulphur coal for home heating in London in order to permit export of higher-quality coal, because of the country's tenuous postwar economic situation. The "fog", or smog, was so thick that driving became difficult or impossible.[|[22]]. The extreme reduction in visibility was accompanied by an increase in criminal activity as well as transportation delays and a virtual shut down of the city. During the 4 day period of fog, at least 4,000 people died as a direct result of the weather.[|[23]] 

[[|edit]] Effects on children
Cities around the world with high exposure to air pollutants have the possibility of children living within them to develop asthma, pneumonia and other lower respiratory infections as well as a low initial birth rate. Protective measures to ensure the youths' health are being taken in cities such as [|New Delhi, India] where buses now use compressed natural gas to help eliminate the “pea-soup” smog.[|[24]] Research by the [|World Health Organization] shows there is the greatest concentration of particulate matter particles in countries with low economic world power and high poverty and population rates. Examples of these countries include [|Egypt], [|Sudan], [|Mongolia], and [|Indonesia]. The [|Clean Air Act] was passed in 1970, however in 2002 at least 146 million Americans were living in areas that did not meet at least one of the “criteria pollutants” laid out in the 1997 National Ambient Air Quality Standards.[|[25]] Those pollutants included: ozone, particulate matter, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead. Because children are outdoors more and have higher minute ventilation they are more susceptible to the dangers of air pollution. 

[[|edit]] Health effects in relatively "clean" areas
Even in areas with relatively low levels of air pollution, public health effects can be substantial and costly. This is because effects can occur at very low levels and a large number of people can potentially breathe in such pollutants. A 2005 scientific study for the British Columbia Lung Association showed that a 1% improvement in ambient PM2.5 and ozone concentrations will produce a $29 million in annual savings in the region in 2010[|[26]]. This finding is based on health valuation of lethal (mortality) and sub-lethal (morbidity) effects. 

[[|edit]] Reduction efforts
There are various air pollution control technologies and [|land use planning] strategies available to reduce air pollution. At its most basic level land use planning is 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. Efforts to reduce pollution from mobile sources includes primary regulation (many developing countries have permissive regulations),[//[|citation needed]//] expanding regulation to new sources (such as [|cruise] and transport ships, farm equipment, and small gas-powered equipment such as lawn trimmers, [|chainsaws], and [|snowmobiles]), increased fuel efficiency (such as through the use of [|hybrid vehicles]), conversion to cleaner fuels (such as [|bioethanol], [|biodiesel], or conversion to electric vehicles). 

[[|edit]] Control devices
The following items are commonly used as pollution control devices by industry or transportation devices. 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 particulate matter 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]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]
 * [|NOx control]**
 * [|Low 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], such as [|activated carbon]
 * [|Flares]
 * [|Thermal oxidizers]
 * [|Catalytic oxidizers]
 * [|Biofilters]
 * [|Absorption (scrubbing)]
 * [|Cryogenic condensers]
 * [|Vapor recovery systems]
 * [|Acid Gas]/[|SO2] control**
 * [|Wet scrubbers]
 * [|Dry scrubbers]
 * [|Flue gas desulfurization]
 * [|Mercury] control**
 * [|Sorbent Injection Technology]
 * [|Electro-Catalytic Oxidation] (ECO)
 * [|K-Fuel]
 * [|Dioxin] and [|furan] control
 * Miscellaneous associated equipment**
 * [|Source capturing systems]
 * [|Continuous emissions monitoring systems] (CEMS)
 * [|Dioxin] and [|furan] control
 * Miscellaneous associated equipment**
 * [|Source capturing systems]
 * [|Continuous emissions monitoring systems] (CEMS)
 * [|Continuous emissions monitoring systems] (CEMS)

[[|edit]] Legal regulations
 Smog in Cairo In general, there are two types of air quality standards. The first class of standards (such as the U.S. [|National Ambient Air Quality Standards]) 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 American [|Air 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. 
 *  || The examples and perspective in this article may not represent a [|worldwide view] of the subject**. Please [|improve this article] or discuss the issue on the [|talk page].** ||

[[|edit]] Canada
In Canada, air quality is typically evaluated against standards set by the [|Canadian Council of Ministers of the Environment] (CCME), an inter-governmental body of federal, provincial and territorial Ministers responsible for the environment. The CCME has set [|Canada Wide Standards](CWS).[|[27]][|[28]] These are:

Note that there is no consequence in Canada to not achieving these standards. In addition, these only apply to jurisdictions with populations greater than 100,000. Further, provinces and territories may set more stringent standards than those set by the CCME. 
 * CWS for PM2.5 **= 30 µg/m3 (24 hour averaging time, by year 2010, based on 98th percentile ambient measurement annually, averaged over 3 consecutive years).**
 * CWS for ozone** = 65 ppb (8-hour averaging time, by year 2010, achievement is based on the 4th highest measurement annually, averaged over 3 consecutive years).

[[|edit]] European Union
A report from the European Environment Agency shows that [|road transport] remains Europe’s single largest air polluter [|[29]]. National Emission Ceilings (NEC) for certain atmospheric pollutants are regulated by Directive 2001/81/EC (NECD).[|[30]] As part of the preparatory work associated with the revision of the NECD, the [|European Commission] is assisted by the NECPI working group (National Emission Ceilings – Policy Instruments).[|[31]] [|Directive 2008/50/EC] of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe (the new Air Quality Directive) has entried into force 2008-06-11 [|[32]]. Individual citizens can force their local councils to tackle air pollution, following an important ruling in July 2009 from the [|European Court of Justice] (ECJ). The EU’s court was asked to judge the case of a resident of Munich, [|Dieter Janecek], who said that under the 1996 EU Air Quality Directive ([|Council Directive 96/62/EC] of 27 September 1996 on ambient air quality assessment and management [|[33]]) the [|Munich] authorities were obliged to take action to stop pollution exceeding specified targets. Janecek then took his case to the ECJ, whose judges said European citizens are entitled to demand air quality action plans from local authorities in situations where there is a risk that EU limits will be overshot. [|[29]]. 

[[|edit]] United Kingdom
Air quality targets set by the [|UK's Department for Environment, Food and Rural Affairs (DEFRA)] are mostly aimed at local government representatives responsible for the management of air quality in cities, where air quality management is the most urgent. The UK has established an air quality network where levels of the key air pollutants[|[34]] are published by monitoring centers.[|[35]] Air quality in [|Oxford], [|Bath] and London[|[36]] is particularly poor. One controversial study[|[37]] performed by the [|Calor Gas company] and published in [|the Guardian newspaper] compared walking in Oxford on an average day to smoking over sixty light cigarettes. More precise comparisons can be collected from the UK Air Quality Archive[|[38]] which allows the user to compare a cities management of pollutants against the national air quality objectives[|[39]] set by DEFRA in 2000. Localized peak values are often cited, but average values are also important to human health. The UK National Air Quality Information Archive offers almost real-time monitoring of "current maximum" air pollution measurements for many UK towns and cities.[|[40]] This source offers a wide range of constantly updated data, including: DEFRA acknowledges that air pollution has a significant effect on health and has produced a simple banding index system[|[41]] is used to create a daily warning system that is issued by the [|BBC] Weather Service to indicate air pollution levels.[|[42]] DEFRA has published guidelines for people suffering from respiratory and heart diseases.[|[43]] 
 * Hourly Mean Ozone (µg/m³)
 * Hourly Mean Nitrogen dioxide (µg/m³)
 * Maximum 15-Minute Mean Sulphur dioxide (µg/m³)
 * 8-Hour Mean Carbon monoxide (mg/m³)
 * 24-Hour Mean PM10 (µg/m³ Grav Equiv)

[[|edit]] United States
 Looking down from the [|Hollywood Hills], with [|Griffith Observatory] on the hill in the foreground, air pollution is visible in downtown [|Los Angeles] on a late afternoon. In the 1960s, 70s, and 90s, the [|United States Congress] enacted a series of [|Clean Air Acts] which significantly strengthened regulation of air pollution. Individual U.S. states, some European nations and eventually the [|European Union] followed these initiatives. The Clean Air Act sets numerical limits on the concentrations of a basic group of air pollutants and provide reporting and enforcement mechanisms. In 1999, the United States [|EPA] replaced the Pollution Standards Index (PSI) with the [|Air Quality Index] (AQI) to incorporate new PM2.5 and Ozone standards. The effects of these laws have been very positive. In the United States between 1970 and 2006, citizens enjoyed the following reductions in annual pollution emissions:[|[44]] In an October 2006 letter to [|EPA], the agency's independent scientific advisors warned that the ozone smog standard “needs to be substantially reduced” and that there is “no scientific justification” for retaining the current, weaker standard. The scientists unanimously recommended a smog threshold of 60 to 70 ppb after they conducted an extensive review of the evidence. [|[45]] The [|EPA] has proposed, in June 2007, a new threshold of 75 ppb. This is less strict than the scientific recommendation, but is more strict than the current standard. Some industries are lobbying to keep the current standards in place. Environmentalists and public health advocates are mobilizing to support the scientific recommendations.[//[|citation needed]//] The [|National Ambient Air Quality Standards] are pollution thresholds which trigger mandatory remediation plans by state and local governments, subject to enforcement by the EPA. An outpouring of dust layered with man-made sulfates, smog, industrial fumes, carbon grit, and nitrates is crossing the [|Pacific Ocean] on prevailing winds from booming Asian economies in plumes so vast they alter the climate. Almost a third of the air over Los Angeles and [|San Francisco] can be traced directly to [|Asia]. With it comes up to three-quarters of the black carbon particulate pollution that reaches the [|West Coast]. [|[46]] [|Libertarians] typically suggest [|propertarian] methods of stopping pollution. They advocate [|strict liability] which would hold accountable anyone who causes polluted air to emanate into someone else's airspace. This offense would be considered aggression, and damages could be sought in court under the [|common law], possibly through [|class action] suits.[|[47]] Since in a libertarian society, highways would be privatized under a system of [|free market roads], the highway owners would also be held liable for pollution emanating from vehicles traveling along their property. This would give them a financial incentive to keep the worst polluters off of their roads. 
 * carbon monoxide emissions fell from 197 million tons to 89 million tons
 * nitrogen oxide emissions fell from 27 million tons to 19 million tons
 * sulfur dioxide emissions fell from 31 million tons to 15 million tons
 * particulate emissions fell by 80%
 * lead emissions fell by more than 98%

[[|edit]] Statistics

 *  || This section requires [|expansion]. ||

[[|edit]] Most polluted cities
Air pollution is usually concentrated in densely populated metropolitan areas, especially in developing countries where environmental regulations are relatively lax or nonexistent. However, even populated areas in developed countries attain unhealthy levels of pollution. 

[[|edit]] Carbon dioxide emissions
matter, μg/m³ (2004) ||~ City || Total CO2 emissions 106 Tons of [|CO2] per year:[|[49]] Per capita CO2 emissions Tons of CO2 per year per capita:[|[49]] 
 * ~ Most Polluted World Cities by PM[|[48]] ||
 * ~ [|Particulate]
 * 169 || [|Cairo, Egypt] ||
 * 150 || [|Delhi, India] ||
 * 128 || [|Kolkata, India] (Calcutta) ||
 * 125 || [|Tianjin, China] ||
 * 123 || [|Chongqing, China] ||
 * 109 || [|Kanpur, India] ||
 * 109 || [|Lucknow, India] ||
 * 104 || [|Jakarta, Indonesia] ||
 * 101 || [|Shenyang, China] ||
 * United States: 2,795
 * China: 2,680
 * Russia: 661
 * India: 583
 * Japan: 415
 * Germany: 356
 * Australia: 300
 * South Africa: 232
 * United Kingdom: 212
 * South Korea: 185
 * Australia: 10
 * United States: 8.2
 * United Kingdom: 3.2
 * China: 1.8
 * India: 0.5

[[|edit]] Atmospheric dispersion
Main article: [|Atmospheric dispersion modeling] The basic technology for analyzing air pollution is through the use of a variety of [|mathematical models] for predicting the transport of air pollutants in the lower atmosphere. The principal methodologies are:   Visualization of a buoyant Gaussian air pollution dispersion plume as used in many atmospheric dispersion models The point source problem is the best understood, since it involves simpler mathematics and has been studied for a long period of time, dating back to about the year 1900. It uses a [|Gaussian] dispersion model for buoyant pollution plumes to forecast the air pollution [|isopleths], with consideration given to wind velocity, stack height, emission rate and stability class (a measure of atmospheric [|turbulence]).[|[50]][|[51]] This model has been extensively validated and calibrated with experimental data for all sorts of atmospheric conditions. The [|roadway air dispersion model] was developed starting in the late 1950s and early 1960s in response to requirements of the [|National Environmental Policy Act] and the [|U.S. Department of Transportation] (then known as the Federal Highway Administration) to understand impacts of proposed new highways upon air quality, especially in urban areas. Several research groups were active in this model development, among which were: the Environmental Research and Technology (ERT) group in [|Lexington, Massachusetts], the ESL Inc. group in [|Sunnyvale, California] and the [|California Air Resources Board] group in [|Sacramento, California]. The research of the ESL group received a boost with a contract award from the [|United States Environmental Protection Agency] to validate a line source model using [|sulfur hexafluoride] as a tracer gas. This program was successful in validating the line source model developed by ESL inc. Some of the earliest uses of the model were in court cases involving highway air pollution, the [|Arlington, Virginia] portion of [|Interstate 66] and the [|New Jersey Turnpike] widening project through [|East Brunswick, New Jersey]. Area source models were developed in 1971 through 1974 by the ERT and ESL groups, but addressed a smaller fraction of total air pollution emissions, so that their use and need was not as widespread as the line source model, which enjoyed hundreds of different applications as early as the 1970s. Similarly photochemical models were developed primarily in the 1960s and 1970s, but their use was more specialized and for regional needs, such as understanding smog formation in [|Los Angeles], [|California]. 
 * [|Point source] dispersion, used for industrial sources.
 * [|Line source] dispersion, used for airport and [|roadway air dispersion modeling]
 * [|Area source] dispersion, used for [|forest fires] or [|duststorms]
 * [|Photochemical] models, used to analyze reactive pollutants that form smog

[[|edit]] Environmental impacts of //greenhouse gas// pollutants
Main articles: [|Ocean acidification] and [|Greenhouse effect] The [|greenhouse effect] is a phenomenon whereby [|greenhouse gases] create a condition in the upper atmosphere causing a trapping of [|heat] and leading to increased surface and lower [|tropospheric] temperatures. Carbon dioxide from combustion of [|fossil fuels] is the major problem. Other greenhouse gases include methane, [|hydrofluorocarbons], [|perfluorocarbons], [|chlorofluorocarbons], [|nitrogen oxides], and [|ozone]. This effect has been understood by scientists for about a century, and technological advancements during this period have helped increase the breadth and depth of data relating to the phenomenon. Currently, scientists are studying the role of changes in composition of greenhouse gases from natural and anthropogenic sources for the effect on [|climate change]. A number of studies have also investigated the potential for long-term rising levels of atmospheric carbon dioxide to cause [|increases in the acidity of ocean waters] and the possible effects of this on marine ecosystems.

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