Air pollution

Air pollution from World War II production.
Smog over Santiago

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.

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.

Indoor air pollution and urban air quality are listed as two of the world's worst pollution problems in the 2008 Blacksmith Institute World's Worst Polluted Places report.[1]

Contents

Pollutants

Main articles: Pollutant and Greenhouse gas
Before flue gas desulfurization was installed, the emissions from this power plant in New Mexico contained excessive amounts of sulfur dioxide.
Schematic drawing, causes and effects of air pollution: (1) greenhouse effect, (2) particulate contamination, (3) increased UV radiation, (4) acid rain, (5) increased ozone concentration, (6) increased levels of nitrogen oxides

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.[2]

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.

Sources

Dust storm approaching Stratford, Texas
Controlled burning of a field outside of Statesboro, Georgia in preparation for spring planting

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

Natural sources

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.[6] The United Kingdom, Australia, Canada and many other countries have published similar compilations, as well as the European Environment Agency.[7][8][9][10][11]

Indoor air quality (IAQ)

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.[12] 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.

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.[13] "Epidemiological studies suggest that more than 500,000 Americans die each year from cardiopulmonary disease linked to breathing fine particle air pollution. . ."[14] A study by the University of Birmingham has shown a strong correlation between pneumonia related deaths and air pollution from motor vehicles.[15] Worldwide more deaths per year are linked to air pollution than to automobile accidents. Published in 2005 suggests that 310,000 Europeans die from air pollution annually. Direct causes of air pollution related deaths include aggravated asthma, bronchitis, emphysema, lung and heart diseases, and respiratory allergies. 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.

The worst short term civilian pollution crisis in India was the 1984 Bhopal Disaster.[16] 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. 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. 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. 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.[17]

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.

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.[18]

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.[19][20] This serves as a plausible mechanistic link between the previously described association between particulate matter air pollution and increased cardiovascular morbidity and mortality.

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.[21] 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. 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.[22]

Effects on COPD

Main article: Chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) include diseases such as chronic bronchitis, emphysema, and some forms of asthma.[23]

A study conducted in 1960-1961 in the wake of the Great Smog of 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, 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, so concluded that air pollution was the most likely cause of the observed differences.[24]

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.[25]

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.[26] 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.[27] 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.

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.[28] This finding is based on health valuation of lethal (mortality) and sub-lethal (morbidity) effects.

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), 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).

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 scrubbersWet 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)

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.

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.

Carbon dioxide emissions

Most Polluted World Cities by PM[29]
Particulate
matter,
μg/m³ (2004)		 City
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
Total CO2 emissions
Countries with the highest CO2 emissions
Country Carbon dioxide emissions per
year (106 Tons) (2006)		 Percentage of global total
 China 6,103 21.5%
 United States 5,752 20.2%
 Russia 1,564 5.5%
 India 1,510 5.3%
 Japan 1293 4.6%
 Germany 805 2.8%
 United Kingdom 568 2.0%
 Canada 544 1.9%
 South Korea 475 1.7%
 Italy 474 1.7%


Per capita CO2 emissions[30]
Countries with the highest per capita CO2 emissions
Country Carbon dioxide emissions per year
(Tons per person) (2006)
 Qatar 56.2
 United Arab Emirates 32.8
 Kuwait 31.2
 Bahrain 28.8
 Trinidad and Tobago 25.3
 Luxembourg 24.5
 Netherlands Antilles 22.8
 Aruba 22.3
 United States 19
 Australia 18.1


Atmospheric dispersion

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).[31][32] 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.

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.

See also

  • Acid rain
  • Air Hygiene Foundation
  • Air pollutant concentrations
  • Air Quality Index
  • Air stagnation
  • AP 42 Compilation of Air Pollutant Emission Factors
  • ASEAN Agreement on Transboundary Haze Pollution
  • Asian brown cloud
  • Atmospheric chemistry
  • Atmospheric dispersion modeling
  • Beehive burner
  • Best Available Control Technology
  • Bibliography of atmospheric dispersion modeling
  • Building biology
  • List of atmospheric dispersion models
  • Critical load
  • Emission standard
  • Emissions & Generation Resource Integrated Database (eGRID)
  • Environmental agreement
  • Flue gas desulfurization
  • Flue gas emissions from fossil fuel combustion
  • Global Atmosphere Watch
  • Global dimming
  • Global warming
  • Greenhouse effect
  • Health Effects Institute (HEI)
  • Indicator value
  • International Agency for Research on Cancer
  • Kyoto Protocol
  • Light water reactor sustainability
  • List of natural disasters by death toll#Smog
  • Lowest Achievable Emissions Rate
  • NASA Clean Air Study
  • Particulate
  • Polluter pays principle
  • Smog and Haze
  • Stench
  • Tire fire

References

  1. ↑ "Reports". WorstPolluted.org. http://www.worstpolluted.org/. Retrieved 2010-08-29. 
  2. ↑ "EPA: Air Pollutants". Epa.gov. 2006-06-28. http://www.epa.gov/ebtpages/airairpollutants.html. Retrieved 2010-08-29. 
  3. ↑ Evidence growing of air pollution’s link to heart disease, death // American Heart Association. May 10, 2010
  4. ↑ "Newly detected air pollutant mimics damaging effects of cigarette smoke" (PDF). http://www.physorg.com/pdf138201201.pdf. Retrieved 2010-08-29. 
  5. ↑ "Infant Inhalation Of Ultrafine Air Pollution Linked To Adult Lung Disease". Sciencedaily.com. 2009-07-23. http://www.sciencedaily.com/releases/2009/07/090722123751.htm. Retrieved 2010-08-29. 
  6. ↑ "AP 42, Volume I". Epa.gov. http://www.epa.gov/ttn/chief/ap42/index.html. Retrieved 2010-08-29. 
  7. ↑ "United Kingdom's emission factor database". Naei.org.uk. http://www.naei.org.uk/emissions/index.php. Retrieved 2010-08-29. 
  8. ↑ European Environment Agency's 2005 Emission Inventory Guidebook
  9. ↑ "Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (reference manual)". Ipcc-nggip.iges.or.jp. http://www.ipcc-nggip.iges.or.jp/public/gl/invs6.htm. Retrieved 2010-08-29. 
  10. ↑ Australian National Pollutant Inventory Emissions Estimation Technique Manuals
  11. ↑ Canadian GHG Inventory Methodologies
  12. ↑ "Duflo, E., Greenstone, M., and Hanna, R. (2008) “Indoor air pollution, health and economic well-being”. ''S.A.P.I.EN.S.'' '''1''' (1)". Sapiens.revues.org. http://sapiens.revues.org/index130.html. Retrieved 2010-08-29. 
  13. ↑ "Estimated deaths & DALYs attributable to selected environmental risk factors, by WHO Member State, 2002". http://www.who.int/entity/quantifying_ehimpacts/countryprofilesebd.xls. Retrieved 2010-08-29. 
  14. ↑ "Newly detected air pollutant mimics damaging effects of cigarette smoke". www.eurekalert.org. http://www.eurekalert.org/pub_releases/2008-08/acs-nda072308.php. Retrieved 2008-08-17. 
  15. ↑ "Study links traffic pollution to thousands of deaths". The Guardian (London, UK: Guardian Media Group). 2008-04-15. http://www.guardian.co.uk/society/2008/apr/15/health. Retrieved 2008-04-15. 
  16. ↑ Simi Chakrabarti. "20th anniversary of world's worst industrial disaster". Australian Broadcasting Corporation. http://www.abc.net.au/worldtoday/content/2004/s1257352.htm. 
  17. ↑ Davis, Devra (2002). When Smoke Ran Like Water: Tales of Environmental Deception and the Battle Against Pollution. Basic Books. ISBN 0-465-01521-2. 
  18. ↑ http://www.sacbee.com/378/story/1393268.html , http://www.latimes.com/features/health/la-me-pollute13-2008nov13,0,5432723.story , http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/11/13/MNQP143CPV.DTL
  19. ↑ Diesel exhaust inhalation increases thrombus formation in man† Andrew J. Lucking1*, Magnus Lundback2, Nicholas L. Mills1, Dana Faratian1, Stefan L. Barath2, Jamshid Pourazar2, Flemming R. Cassee3, Kenneth Donaldson1, Nicholas A. Boon1, Juan J. Badimon4, Thomas Sandstrom2, Anders Blomberg2, and David E. Newby1
  20. ↑ Persistent Endothelial Dysfunction in Humans after Diesel Exhaust Inhalation Ha°kan To¨rnqvist1*, Nicholas L. Mills2*, Manuel Gonzalez3, Mark R. Miller2, Simon D. Robinson2, Ian L. Megson4, William MacNee5, Ken Donaldson5, Stefan So¨derberg3, David E. Newby2, Thomas Sandstro¨m1, and Anders Blomberg1
  21. ↑ Christopher H. Goss, Stacey A. Newsom, Jonathan S. Schildcrout, Lianne Sheppard and Joel D. Kaufman (2004). "Effect of Ambient Air Pollution on Pulmonary Exacerbations and Lung Function in Cystic Fibrosis". American Journal of Respiratory and Critical Care Medicine 169 (7): 816–821. doi:10.1164/rccm.200306-779OC. PMID 14718248. 
  22. ↑ Michael Kymisis, Konstantinos Hadjistavrou (2008). "Short-Term Effects Of Air Pollution Levels On Pulmonary Function Of Young Adults". The Internet Journal of Pulmonary Medicine 9 (2). http://www.ispub.com/ostia/index.php?xmlFilePath=journals/ijpm/vol9n2/pollution.xml. 
  23. ↑ Zoidis, John D. (1999). "The Impact of Air Pollution on COPD". RT: for Decision Makers in Respiratory Care. http://www.rtmagazine.com/issues/articles/1999-10_06.asp. 
  24. ↑ Holland WW, Reid DD. The urban factor in chronic bronchitis. Lancet. 1965;I:445-448.
  25. ↑ J. Sunyer (2001). "Urban air pollution and Chronic Obstructive Pulmonary disease: a review". European Respiratory Journal 17 (5): 1024–1033. doi:10.1183/09031936.01.17510240. PMID 11488305. http://erj.ersjournals.com/cgi/content/abstract/17/5/1024. 
  26. ↑ "Polluted Cities: The Air Children Breathe" (PDF). World Health Organization. http://www.who.int/ceh/publications/en/11airpollution.pdf. 
  27. ↑ Committee on Environmental Health (2004). "Ambient Air Pollution: Health Hazards to Children". Pediatrics 114 (6): 1699–1707. doi:10.1542/peds.2004-2166. PMID 15574638. 
  28. ↑ "2005 BC Lung Association report on the valuation of health impacts from air quality in the Lower Fraser Valley airshed" (PDF). http://www.bc.lung.ca/pdf/health_and_air_quality_2005.pdf. Retrieved 2010-08-29. 
  29. ↑ "World Bank Statistics" (PDF). http://siteresources.worldbank.org/DATASTATISTICS/Resources/table3_13.pdf. Retrieved 2010-08-29. 
  30. ↑ International Carbon Dioxide Emissions and Carbon Intensity Energy Information Administration
  31. ↑ Turner, D.B. (1994). Workbook of atmospheric dispersion estimates: an introduction to dispersion modeling (2nd ed.). CRC Press. ISBN 1-56670-023-X. 
  32. ↑ Beychok, M.R. (2005). Fundamentals Of Stack Gas Dispersion (4th ed.). author-published. ISBN 0-9644588-0-2.  www.air-dispersion.com

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