Smog

Smog 1

Smog

Smog in New York City as viewed from theWorld Trade Center in 1988

German road sign, Verkehrsverbot bei Smog (Notraffic allowed in smog conditions)

Smog is a type of air pollution; the word "smog" is a portmanteau ofsmoke and fog. Modern smog is a type of air pollution derived fromvehicular emission from internal combustion engines and industrialfumes that react in the atmosphere with sunlight to form secondarypollutants that also combine with the primary emissions to formphotochemical smog. Smog is also caused by large amounts of coalburning in an area caused by a mixture of smoke and sulfur dioxide.

Origin of term

Coinage of the term "smog" is generally attributed to Dr. HenryAntoine Des Voeux in his 1905 paper, "Fog and Smoke" for a meetingof the Public Health Congress. The July 26, 1905 edition of theLondon newspaper Daily Graphic quoted Des Voeux, "He said itrequired no science to see that there was something produced in greatcities which was not found in the country, and that was smoky fog, orwhat was known as 'smog.'"[1] The following day the newspaper statedthat "Dr. Des Voeux did a public service in coining a new word for theLondon fog." "Smog" also appears in a January 19, 1893, Los AngelesTimes article and is attributed to "a witty English writer."

Photochemical smog

Smog in the Syrian city of Aleppo, summer 2006

In the 1950s a new type of smog, known as photochemical smog, wasfirst described. The compound when sunlight hits various pollutants inthe air and forms a mix of inimical chemicals that can be verydangerous. A photochemical smog is the chemical reaction of sunlight,nitrogen oxides (NOx) and volatile organic compounds (VOCs) in theatmosphere, which leaves airborne particles (called particulate matter)and ground-level ozone.[2]

Nitrogen oxides are released by nitrogen and oxygen in the air reactingtogether under high temperature such as in the exhaust of fossilfuel-burning engines in cars, trucks, coal power plants, and industrialmanufacturing factories. VOCs are released from man-made sourcessuch as gasoline (petrol), paints, solvents, pesticides, and biogenicsources, such as pine and citrus tree emissions.

This noxious mixture of air pollutants can include the following:• Aldehydes (RCHO)

Smog 2

• Nitrogen oxides, such as nitrogen dioxide• Peroxyacyl nitrates (PAN)• Tropospheric ozone• Volatile organic compounds (VOCs)All of these chemicals are usually highly reactive and oxidizing. Photochemical smog is therefore considered to be aproblem of modern industrialization. It is present in all modern cities, but it is more common in cities with sunny,warm, dry climates and a large number of motor vehicles.[3] Because it travels with the wind, it can affect sparselypopulated areas as well.

Characteristic coloration for smog in California in the beige cloud bank behind Golden Gate Bridge. The brown coloration is due to the NOx in thephotochemical smog.

Health effects

Highland Park Optimist Club wearing smog-gasmasks at banquet, Los Angeles, circa 1954

Smog is a serious problem in many cities and continues to harm humanhealth.[4] Ground-level ozone, sulfur dioxide, nitrogen dioxide andcarbon monoxide are especially harmful for senior citizens, children,and people with heart and lung conditions such as emphysema,bronchitis, and asthma.[5] It can inflame breathing passages, decreasethe lungs' working capacity, cause shortness of breath, pain wheninhaling deeply, wheezing, and coughing. It can cause eye and noseirritation and it dries out the protective membranes of the nose andthroat and interferes with the body's ability to fight infection,increasing susceptibility to illness. Hospital admissions and respiratorydeaths often increase during periods when ozone levels are high.[6]

The U.S. EPA has developed an Air Quality Index to help explain airpollution levels to the general public. 8 hour average ozone mole fractions of 85 to 104 nmol/mol are described as"Unhealthy for Sensitive Groups", 105 nmol/mol 124 nmol/mol as "unhealthy" and 125 nmol/mol to 404 nmol/molas "very unhealthy".[7] The "very unhealthy" range for some other pollutants are: 355 μg m−3 - 424 μg m−3 forPM10; 15.5 μmol/mol - 30.4 μmol/mol for CO and 0.65 μmol/mol - 1.24 μmol/mol for NO2.[8]

The Ontario Medical Association announced that smog is responsible for an estimated 9,500 premature deaths in theprovince each year.[9]

A 20-year American Cancer Society study found that cumulative exposure also increases the likelihood of prematuredeath from a respiratory disease, implying the 8-hour standard may be insufficient.[10]

Smog 3

Areas affected

Beijing air on a day after rain (left) and a smoggyday (right)

Smog can form in almost any climate where industries or cities releaselarge amounts of air pollution, such as smoke or gases. However, it isworse during periods of warmer, sunnier weather when the upper air iswarm enough to inhibit vertical circulation. It is especially prevalent ingeologic basins encircled by hills or mountains. It often stays for anextended period of time over densely populated cities or urban areas,such as London, Atlanta, Houston, Phoenix, Las Vegas, New Delhi,New York, Cairo, Los Angeles, Sacramento, São Paulo, Mexico City,Santiago of Chile, Toronto, Milan, Athens, Beijing, Shanghai, Manila, Hong Kong, Seoul, the Randstad or RuhrArea and can build up to dangerous levels.

London

Victorian London was notorious for its thicksmogs, or "pea-soupers", a fact that is often

recreated to add an air of mystery to a periodcostume drama

In 1306, concerns over air pollution were sufficient for Edward I to(briefly) ban coal fires in London.[11] In 1661, John Evelyn'sFumifugium suggested burning fragrant wood instead of mineral coal,which he believed would reduce coughing. The Ballad of GreshamCollege the same year describes how the smoke "does our lungs andspirits choke, Our hanging spoil, and rust our iron."

Severe episodes of smog continued in the 19th and 20th centuries andwere nicknamed "pea-soupers". The Great Smog of 1952 darkened thestreets of London and killed approximately 4,000 people in the shorttime of 4 days (a further 8,000[12] died from its effects in the followingweeks and months). Initially a flu epidemic was blamed for the loss oflife. In 1956 the Clean Air Act introduced smokeless zones in thecapital. Consequently, reduced sulfur dioxide levels made the intenseand persistent London smog a thing of the past. It was after this thegreat clean-up of London began and buildings recovered their originalstone façades which, during two centuries, had gradually blackened.Smog caused by traffic pollution, however, does occur in modernLondon.

Mexico City

Due to its location in a highland "bowl", cold air sinks down onto the urban area of Mexico City, trapping industrialand vehicle pollution underneath, and turning it into the most infamously smog-plagued city of Latin America.Within one generation, the city has changed from being known for some of the cleanest air of the world into onewith some of the worst pollution, with pollutants like nitrogen dioxide being double or even triple internationalstandards.[13]

Smog 4

Photochemical Smog Over Mexico CityDecember 2010.

Tehran

In December 2005, schools and public offices had to close in Tehran,Iran and 1600 people were taken to hospital, in a severe smog blamedlargely on unfiltered car exhaust.[14]

United States

A NASA astronaut photograph of a smog layerover central New York.

Counties in the United States where one or moreNational Ambient Air Quality Standards are not

met, as of June 2007.

Smog was brought to the attention of the general US public in 1933with the publication of the book "Stop That Smoke", by HenryObermeyer, a New York public utility official, in which he pointed outthe effect on human life and even the destruction of a farmers 3000acres of spinach crop.[15] Since then, the United States EnvironmentalProtection Agency has designated over 300 U.S. counties to benon-attainment areas for one or more pollutants tracked as part of theNational Ambient Air Quality Standards.[16] These areas are largelyclustered around large metropolitan areas, with the largest contiguousnon-attainment zones in California and the Northeast. Various U.S. andCanadian government agencies collaborate to produce real-time airquality maps and forecasts.[17]

Los Angeles and the San Joaquin Valley

Being in low basins surrounded by mountains, Los Angeles and theSan Joaquin Valley are notorious for their smog. The millions ofvehicles in these basins plus the added effects of the San Francisco Bayand Los Angeles/Long Beach port complexes contribute to further airpollution. While strict regulations by the multiple Californiagovernment agencies overseeing this problem have reduced thenumber of Stage 1 smog alerts from several hundred annually to just afew, these geologically predisposed entrapment zones collect pollutionlevels from cars, trucks and fixed sources which still exceeds healthstandards and is a pressing issue for the more than 25 million peoplewho live there.

Major incidents in the US

• 1948, October 30–31, Donora, PA: 20 died, 600 hospitalized, thousands more stricken. Lawsuits were not settleduntil 1951.[18]

• 1953, November, New York: Smog kills between 170 and 260 people.[18]

• 1954, October, Los Angeles: heavy smog shuts down schools and industry for most of the month.[18]

Smog 5

• 1963, New York: blamed for 200 deaths [19]

• 1966, New York: blamed for 169 deaths [19]

Southeast Asia

Singapore's Downtown Core on 7 October 2006,when it was affected by forest fires in Sumatra,

Indonesia

Smog is a regular problem in Southeast Asia caused by land and forestfires in Indonesia, especially Sumatra and Kalimantan, although theless political term haze is preferred in describing the problem. Farmersand plantation owners are usually responsible for the fires, which theyuse to clear tracts of land for further plantings. Those fires mainlyaffect Brunei, Indonesia, Philippines, Malaysia, Singapore andThailand, and occasionally Guam and Saipan.[20] [21] The economiclosses of the fires in 1997 have been estimated at more than US$9billion.[22] This includes damages in agriculture production,destruction of forest lands, health, transportation, tourism, and othereconomic endeavours. Not included are social, environmental, andpsychological problems and long-term health effects. The latest bout of

haze to occur in Malaysia, Singapore and the Malacca Straits is in October 2006, and was caused by smoke fromfires in Indonesia being blown across the Straits of Malacca by south-westerly winds.

The Association of Southeast Asian Nations (ASEAN) reacted and signed Agreement on Transboundary HazePollution, formed a Regional Haze Action Plan (RHAP) and established a co-ordination and support unit (CSU).[23]

RHAP, with the help of Canada, established a monitoring and warning system for forest/vegetation fires andimplemented a Fire Danger Rating System (FDRS). The Malaysian Meteorological Service (MMS)[24] has issued adaily rating since September 2003. The Indonesians have been ineffective at enforcing legal policies on errantfarmers.

Natural causesAn erupting volcano can also emit high levels of sulphur dioxide along with a large quantity of particulate matter;two key components to the creation of smog. However, the smog created as a result of a volcanic eruption is oftenknown as "vog" to distinguish it as a natural occurrence.The radiocarbon content of some plant life has been linked to the distrobution of smog in some areas. For example;presence of Creosote bush in the Los Angeles area has been shown to have an effect on smog distribution that ismore than fossil fuel combustion alone.[25]

Smog 6

Pollution index

Smog in São Paulo

The severity of smog is often measured using automated opticalinstruments such as Nephelometers, as haze is associated withvisibility and traffic control in ports. Haze however can also be anindication of poor air quality though this is often better reflected usingaccurate purpose built air indexes such as the American Air QualityIndex, the Malaysian API (Air Pollution Index) and the SingaporeanPollutant Standards Index.

In hazy conditions, it is likely that the index will report the suspendedparticulate level. The disclosure of the responsible pollutant ismandated in some jurisdictions.The Malaysian API does not have a capped value; hence its mosthazardous readings can go above 500. Above 500, a state of emergency is declared in the affected area. Usually, thismeans that non-essential government services are suspended, and all ports in the affected area are closed. There mayalso be prohibitions on private sector commercial and industrial activities in the affected area excluding the foodsector. So far, state of emergency rulings due to hazardous API levels were applied to the Malaysian towns of PortKlang, Kuala Selangor and the state of Sarawak during the 2005 Malaysian haze and the 1997 Southeast Asian haze.

Cultural references

Claude Monet made several trips to Londonbetween 1899 and 1901, during which he paintedviews of the Thames and Houses of Parliamentwhich show the sun struggling to shine through

London's smog-laden atmosphere.

• The London "pea-soupers" earned the capital the nickname of "TheSmoke". Similarly, Edinburgh was known as "Auld Reekie". Thesmogs feature in many London novels as a motif indicating hiddendanger or a mystery, perhaps most overtly in Margery Allingham'sThe Tiger in the Smoke (1952), but also in Dickens' Bleak House(1852):

[A]s he handed me into a fly after superintending the removal ofmy boxes, I asked him whether there was a great fire anywhere?For the streets were so full of dense brown smoke that scarcelyanything was to be seen."Oh, dear no, miss," he said. "This is a London particular."I had never heard of such a thing."A fog, miss," said the young gentleman.

—Charles Dickens, Bleak House

• The 1970 made-for-TV movie A Clear and Present Danger, which featured Hal Holbrook, E.G. Marshall, JosephCampanella, Jack Albertson and Pat Hingle, was one of the first American television network entertainmentprograms to warn about the problem of smog and air pollution.[26] (This film is not to be confused with the 1994film with a similar name.)

• 'Smog' or 'Smoggy' has also come into use to describe a resident of Teesside (in North East England) or asupporter of Middlesbrough Football Club, due to the high concentration of chemical and heavy industry in theTeesside area. Although it has now been proven that the Teesside air is cleaner than London, Newcastle,Sunderland and many other British cities, the main source of pollution in the air is now vehicle exhaust fumes,like most urban areas.

• Ulrich Beck, Classic Quote by Ulrich ‘Poverty is hierarchic, smog is democratic’.[27]

Smog 7

• Hedorah, a monster from the Godzilla movie, Godzilla vs. Hedorah, feeds on pollution and is referred to as "TheSmog Monster".

• South Park, The town of South park is beset by smug, in the episode Smug Alert!, a satirical reference to bothsmog and celebrities who wish to prevent environmental degradation.

• The history of smog in LA is detailed in Smogtown by Chip Jacobs and William J. Kelly (Overlook Press).[28]

References[1] Gaia Piazzesi 2006 (http:/ / ega. web. psi. ch/ Piazzesi, PhD thesis, ETH Zurich, 2006. pdf)[2] "What is Smog?", Canadian Council of Ministers of the Environment, CCME.ca (http:/ / www. ccme. ca/ assets/ pdf/ pn_1257_e. pdf)[3] Miller, Jr., George Tyler (2002). Living in the Environment: Principles, Connections, and Solutions (12th Edition). Belmont: The Thomson

Corporation. pp. 423. ISBN 0-534-37697-5.[4] USA Today (http:/ / www. usatoday. com/ weather/ news/ 2004-04-15-air-quality-ap_x. htm)[5] Airnow.gov (http:/ / www. airnow. gov/ index. cfm?action=health2. smog1#4), "Who is most at risk from ozone?"[6] CWAC.net (http:/ / www. cwac. net/ air_pollution/ ozone. html), Ozone in Wisconsin[7] Airnow.gov (http:/ / www. airnow. gov/ index. cfm?action=health2. smog1#4)[8] EPA.gov (http:/ / www. epa. gov/ ttn/ oarpg/ t1/ memoranda/ rg701. pdf)[9] Wheels.ca (http:/ / wheels. ca/ reviews/ article/ 256058), $3.83 to power hybrid plug-in for 6 days[10] NPR.org (http:/ / www. npr. org/ templates/ transcript/ transcript. php?storyId=101694787), Smoggy Skies May Cause Respiratory Death[11] Environmentalgraffiti.com (http:/ / www. environmentalgraffiti. com/ offbeat-news/ environmentalism-in-1306/ 725), Environmentalism in

1306[12] Bell, Michelle L.; Michelle L. Bell, Devra L. Davis, Tony Fletcher (January 2004). "A Retrospective Assessment of Mortality from the

London Smog Episode of 1959: The Role of Influenza and Pollution" (http:/ / www. ehponline. org/ members/ 2003/ 6539/ 6539. html).Environ Health Perspect 112 (1): 6–8. doi:10.1289/ehp.6539. .

[13] SBC.ac.at (http:/ / www. sbg. ac. at/ ipk/ avstudio/ pierofun/ mexico/ air. htm), Air pollution in Mexico City, University of Salzburg[14] "Hundreds treated over Tehran smog" (http:/ / news. bbc. co. uk/ 1/ hi/ world/ middle_east/ 4516430. stm). BBC News. 2005-12-10. .

Retrieved 2006-08-03.[15] "Cities Unit in Concerted Drive Again Air Laden With Health Destroying Impurities", October 1933, Popular Science (http:/ / books.

google. com/ books?id=6CcDAAAAMBAJ& pg=PA29& dq=motor+ gun+ boat& hl=en& ei=6AXqTIOfAsienAf959ngDQ& sa=X&oi=book_result& ct=result& resnum=1& ved=0CC4Q6AEwAA#v=onepage& q=motor gun boat& f=true)

[16] EPA.gov (http:/ / www. epa. gov/ oar/ oaqps/ greenbk/ ), The Green Book Nonattainment Areas, Green Book |[17] Airnow.gov (http:/ / www. airnow. gov)[18] Radford.edu (http:/ / www. radford. edu/ ~wkovarik/ envhist/ 7forties. html), Environmental History Timeline: 1940-1960[19] Washingtonpost.com (http:/ / washingtonpost. findlaw. com/ supreme_court/ briefs/ 99-1257/ 99-1257fo5/ text. html)[20] SaigpanTribune.com (http:/ / www. saipantribune. com/ newsstory. aspx?cat=1& newsID=61706)[21] Sun2Surf.com (http:/ / www. sun2surf. com/ article. cfm?id=15717)[22] Asean.org (http:/ / haze. asean. org/ info/ faq-combatinghaze), ASEAN secreatriat on smog cost[23] Asean.org (http:/ / haze. asean. org/ )[24] KJC.gov.my (http:/ / www. kjc. gov. my/ english/ service/ climate/ afdrs/ fwi. jpg)[25] http:/ / www. sciencedirect. com/ science?_ob=MImg& _imagekey=B6V7X-48XDN58-3H-1& _cdi=5854& _user=7209612&

_pii=0160412081901136& _origin=search& _coverDate=12%2F31%2F1981& _sk=999949998& view=c& wchp=dGLzVzz-zSkzV&md5=b5a34a715396bf9618677e5f389bd00b& ie=/ sdarticle. pdf

[26] IMDb.com (http:/ / imdb. com/ title/ tt0065558/ ), A Clear and Present Danger (1970) (TV)[27] Risk Society: Towards A New Modernity (Sage, 1992)[28] Overlookpress.com (http:/ / www. overlookpress. com/ book-detail. php?book_isbn=1-58567-860-0& last_url=search.

php?search=smogtown/ ), Smogtown, The Lung-Burning History of Pollution in Los Angeles by Chip Jacobs & William J. Kelly

Smog 8

External links• Smog (http:/ / en. citizendium. org/ wiki/ Smog) A Citizendium article• Eoearth.org (http:/ / www. eoearth. org/ article/ London_smog_disaster,_England), London Smog Disaster,

Encyclopedia of Earth• NPI.gov.au (http:/ / www. npi. gov. au/ database/ substance-info/ profiles/ 69. html), National Pollutant Inventory

- Particulate matter fact sheet• Contrails.nl (http:/ / www. contrails. nl), Pictures of Contrails and Aviation Cirrus (- Smog), since 1995 until now.• Ausetute.com.au (http:/ / www. ausetute. com. au/ photsmog. html), Photochemical Smog• Iras.uu.nl (http:/ / airnet. iras. uu. nl/ products/ pdf/ airnet_wg3_toxicology_report. pdf), Airnet Workgroup

Toxicology ReportNews• BBC.co.uk (http:/ / www. bbc. co. uk/ ww2peopleswar/ stories/ 10/ a4914010. shtml), "When smog was a

frequent occurrence, WW2 People's War, BBC 2005-08-10. Accessed 2006-08-03.

Article Sources and Contributors 9

Article Sources and ContributorsSmog  Source: http://en.wikipedia.org/w/index.php?oldid=417150371  Contributors: 213.112.220.xxx, Aaronkavo, Adrian, Airconswitch, Aitias, Alan Liefting, Alansohn, AlexiusHoratius, Alvis,Amir.h.110, Ancheta Wis, Android Mouse, AndyBQ, Antandrus, Archanamiya, Astral, Atif.t2, Atmoz, Aussie Alchemist, Baan4c, Balthazarduju, Bbik, Beaverfever, Beland, Ben Hateva,Bikeable, Billtubbs, Blue520, BlueEarth, Bobak, Bradleyosborn, Branddobbe, Brianga, BrokenSphere, CGHW1, Calmer Waters, Calvin 1998, CambridgeBayWeather, Camw, Can't sleep, clownwill eat me, CanadianLinuxUser, Capricorn42, Chanub, Ckatz, Cometstyles, CommonsDelinker, Computerjoe, Connelly90, Conversion script, Courcelles, Crazzyninja, Crispmuncher,DabMachine, DaddyT, Daniel.Cardenas, Daniel5127, DanielCD, Dapang, Darth Panda, Dawnseeker2000, Dejvid, DerHexer, DerechoReguerraz, Discospinster, Donikanuhiu, Doodoggy,Dreamyshade, DrumCarton, Dsyzdek, Dysepsion, E2eamon, Earth, EchoBravo, Ed Fitzgerald, Ed g2s, EdH, Edmundosargento, Edson Rosa, Ela.oregon, Element16, Eliot red, Eliz81, Ellywa,Emezei, Emperor Genius, Endroit, Enveconmatt, Enviroboy, Epbr123, Essjay, FaerieInGrey, Farosdaughter, Favonian, Feezo, Fragglet, Franknoppel, Frecklefoot, Fredrik, Freefighter, FrédérickLacasse, Furrykef, Fxhomie, Fyyer, Fæ, Gabriel Kielland, Gaius Cornelius, Garthman69, Gene Nygaard, Giftlite, Gilliam, Gogo Dodo, Graham87, Greggygreggreg, GregorB, Greyyhawkk,Gripper101, Gökhan, HalJor, Hazy, HeHeHaHaLolz, Hei hei, Horrorshowj, Huangdi, Husond, Hut 6.5, Hyperionides, Iain.mcclatchie, Ichakrab, Ingolfson, Irish Pearl, IronGargoyle, Isaac17620,Itsmine, J.delanoy, JForget, JRR Trollkien, Jackehammond, JackyR, Jacob Myers, Jameswilson, Janet Davis, January, Jazzman67, Jclemens, Jebus989, Jerome Charles Potts, JimVC3, JimmySlade, Jkoskie, John Reaves, John67832, Johnfravolda, Jonathunder, Joseph Solis in Australia, Joyous!, Jst123l, Jthain, Jui 221.coollyric, Jusdafax, Kaiser matias, Ke4roh, Keilana, KeithH,Kevorkmail, Kidcudi10, KnowledgeOfSelf, Kpjas, Krapitino, Kusunose, La goutte de pluie, LarryBH, Law, LeaveSleaves, LegitimateAndEvenCompelling, Leonard G., Leuko, Lightmouse,Linnell, Lmharnisch, Lokantha, Lotje, Lowellian, Lph, Mac, Macintosh User, Makemi, Malcolmxl5, Mandarax, Manop, Marco1234, Marqueed, Martial75, Martin451, Mato, Matthew Desjardins,Mbeychok, Mee Goring plus, Mentifisto, Metamagician3000, Mifter, Minimac's Clone, Mintguy, Mitsein, Moon&Nature, Morrisjones, Mr. Wheely Guy, Mridu Verma, My76Strat, Mzhao,N1RK4UDSK714, NHSavage, Nacerak, Nagy, Natural RX, NawlinWiki, Ne0Freedom, Neemaz, Neurolinguist, Nichalp, Nickptar, Nk.sheridan, No Parking, Nopetro, Nut-meg, Nuujinn, OdaMari, Orphan Wiki, Ottava Rima, Oxymoron83, Ozgod, Pascal666, Peterlewis, Petr Kopač, Ph0987, Phil Bridger, Pikazilla, Pinethicket, Pkchan, Pointillist, Possum, PrincessofLlyr, PseudoSudo,Purifier123, Radiojon, RangerOfFire, Rayhusthwaite, Razimantv, RedMabuse, Renato Caniatti, Rettetast, RexNL, Richard Keatinge, RickK, Rmhermen, Ronhjones, Rror, Rvanwaning, SJP,SQGibbon, Saturday, Schnolle, Scoops20, Sean D Martin, Shaddack, Shakil, Shell Kinney, Shoeofdeath, Siim, Silvergallium, Sionus, SkyWalker, Skysmith, Slakr, Slowking Man, Smitz,Smogthepyroking, Smp5000, Snigbrook, Sokari, Sole Soul, Solipsist, Someguy1221, SpikeToronto, SpuriousQ, St.daniel, Stemonitis, StephanieM, Stephen Turner, Stephenb, Stone, Storeye,Stromcarlson, Stu42, Stupid2, Summerbaby201091, Supersquid, Svetovid, Synchronism, Syrthiss, Tarquin, Tarret, Tarsie, Tawker, Templationist, Tghe-retford, The Thing That Should Not Be,TheCatalyst31, Thebigone125, Thegreatdr, Theshibboleth, Thorpe, Tiatona, Tide rolls, Tillman, Towerman, TransUtopian, Treecko 09, Tresiden, Uncle Dick, Valley2city, Vegaswikian,Versus22, Vsmith, Wackywace, Walor, Wavelength, Wereon, Why Not A Duck, Wikidudeman, Wimdit, XVreturns, XalD, Xaliqen, Xezbeth, Y1997xf11, YAWADarren, Yms, Yosri, Yossiea,Zenohockey, Zigger, 781 anonymous edits

Image Sources, Licenses and ContributorsImage:SmogNY.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:SmogNY.jpg  License: Public Domain  Contributors: Gryffindor, Quasipalm, Saperaud, 1 anonymous editsFile:Zeichen 270.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Zeichen_270.svg  License: Public Domain  Contributors: Cfaerber, Cäsium137, UmherirrenderFile:Air pollution in Aleppo summer 2006.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Air_pollution_in_Aleppo_summer_2006.JPG  License: Creative CommonsAttribution-Sharealike 3.0  Contributors: User:AboalbissImage:Lightmatter Golden gate bridge.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Lightmatter_Golden_gate_bridge.jpg  License: unknown  Contributors: By Aaron LoganFile:LA smog masks.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:LA_smog_masks.jpg  License: unknown  Contributors: Original uploader was Tillman at en.wikipediaImage:Beijing smog comparison August 2005.png  Source: http://en.wikipedia.org/w/index.php?title=File:Beijing_smog_comparison_August_2005.png  License: Creative CommonsAttribution-Sharealike 2.5  Contributors: w:en:User:BobakBobakImage:LondonSmog.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:LondonSmog.jpg  License: unknown  Contributors: Bhoeble, BrokenSphere, D-Kuru, Diwas, Jborme, Lobo,Saperaud, SolipsistFile:AerialViewPhotochemicalSmogMexicoCity 2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:AerialViewPhotochemicalSmogMexicoCity_2.jpg  License: Creative CommonsAttribution-Sharealike 3.0  Contributors: TiatonaImage:Upstatenysmog.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Upstatenysmog.jpg  License: Public Domain  Contributors: Original uploader was Nut-meg at en.wikipediaImage:US-overall-nonattainment-2007-06.png  Source: http://en.wikipedia.org/w/index.php?title=File:US-overall-nonattainment-2007-06.png  License: Public Domain  Contributors: Originaluploader was Beland at en.wikipedia. Later version(s) were uploaded by Iain at en.wikipedia.Image:Downtown Core, Singapore, Oct 06.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Downtown_Core,_Singapore,_Oct_06.JPG  License: unknown  Contributors: CommonGood, Jacklee, SengkangImage:Zona Leste - São Paulo-Brasil.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Zona_Leste_-_São_Paulo-Brasil.jpg  License: Creative Commons Attribution-Sharealike 3.0 Contributors: User:Gaf.arqImage:Claude Monet 015.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Claude_Monet_015.jpg  License: Public Domain  Contributors: Anna reg, Ardfern, Bhoeble, Croberto68,Hailey C. Shannon, JackyR, Olivier2, Rlbberlin, Schlurcher, Szilas, The Duke of Waltham

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