air pollution | Effects, Causes, Definition, & Facts | Britannica

The gaseous criteria air pollutants of primary concern in urban settings include sulfur dioxide, nitrogen dioxide, and carbon monoxide; these are emitted ... airpollution TableofContents airpollution IntroductionMajorairpollutantsCriteriapollutantsFineparticulatesCarbonmonoxideSulfurdioxideNitrogendioxideOzoneLeadAirtoxicsGreenhousegasesAirpollutionandairmovementTheglobalreachofairpollutionIndoorairpollution FastFacts 2-MinSummary RelatedContent Media Videos Images More MoreArticlesOnThisTopic Contributors ArticleHistory Home Science Environment airpollution Actions Cite verifiedCite Whileeveryefforthasbeenmadetofollowcitationstylerules,theremaybesomediscrepancies. Pleaserefertotheappropriatestylemanualorothersourcesifyouhaveanyquestions. 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BritannicaWebsites ArticlesfromBritannicaEncyclopediasforelementaryandhighschoolstudents. airpollution-StudentEncyclopedia(Ages11andup) By JerryA.Nathanson • EditHistory TableofContents airpollutioninMexicoCity Seeallmedia RelatedTopics: acidrain atmosphericbrowncloud smog carbonemission icefog ...(Showmore) Seeallrelatedcontent→ Summary Readabriefsummaryofthistopic airpollutioninGurgaon,Indiaairpollution,releaseintotheatmosphereofvariousgases,finelydividedsolids,orfinelydispersedliquidaerosolsatratesthatexceedthenaturalcapacityoftheenvironmenttodissipateanddiluteorabsorbthem.Thesesubstancesmayreachconcentrationsintheairthatcauseundesirablehealth,economic,oraestheticeffects.MajorairpollutantsCriteriapollutantsClean,dryairconsistsprimarilyofnitrogenandoxygen—78percentand21percentrespectively,byvolume.Theremaining1percentisamixtureofothergases,mostlyargon(0.9percent),alongwithtrace(verysmall)amountsofcarbondioxide,methane,hydrogen,helium,andmore.Watervapourisalsoanormal,thoughquitevariable,componentoftheatmosphere,normallyrangingfrom0.01to4percentbyvolume;underveryhumidconditionsthemoisturecontentofairmaybeashighas5percent.TherearesixmajorairpollutantsthathavebeendesignatedbytheU.S.EnvironmentalProtectionAgency(EPA)as“criteria”pollutants—criteriameaningthattheconcentrationsofthesepollutantsintheatmosphereareusefulasindicatorsofoverallairquality.Thesources,acceptableconcentrations,andeffectsofthecriteriapollutantsaresummarizedinthetable. Criteriaairpollutants pollutant commonsources maximumacceptableconcentrationintheatmosphere environmentalrisks humanhealthrisks Source:U.S.EnvironmentalProtectionAgency carbonmonoxide(CO) automobileemissions,fires,industrialprocesses 35ppm(1-hourperiod);9ppm(8-hourperiod) contributestosmogformation exacerbatessymptomsofheartdisease,suchaschestpain;maycausevisionproblemsandreducephysicalandmentalcapabilitiesinhealthypeople nitrogenoxides(NOandNO2) automobileemissions,electricitygeneration,industrialprocesses 0.053ppm(1-yearperiod) damagetofoliage;contributestosmogformation inflammationandirritationofbreathingpassages sulfurdioxide(SO2) electricitygeneration,fossil-fuelcombustion,industrialprocesses,automobileemissions 0.03ppm(1-yearperiod);0.14ppm(24-hourperiod) majorcauseofhaze;contributestoacidrainformation,whichsubsequentlydamagesfoliage,buildings,andmonuments;reactstoformparticulatematter breathingdifficulties,particularlyforpeoplewithasthmaandheartdisease ozone(O3) nitrogenoxides(NOx)andvolatileorganiccompounds(VOCs)fromindustrialandautomobileemissions,gasolinevapours,chemicalsolvents,andelectricalutilities 0.075ppm(8-hourperiod) interfereswiththeabilityofcertainplantstorespire,leadingtoincreasedsusceptibilitytootherenvironmentalstressors(e.g.,disease,harshweather) reducedlungfunction;irritationandinflammationofbreathingpassages particulatematter sourcesofprimaryparticlesincludefires,smokestacks,constructionsites,andunpavedroads;sourcesofsecondaryparticlesincludereactionsbetweengaseouschemicalsemittedbypowerplantsandautomobiles 150μg/m3(24-hourperiodforparticles<10 μm);35μg/m3(24-hourperiodforparticles<2.5μm) contributestoformationofhazeaswellasacidrain,whichchangesthepHbalanceofwaterwaysanddamagesfoliage,buildings,andmonuments irritationofbreathingpassages,aggravationofasthma,irregularheartbeat lead(Pb) metalprocessing,wasteincineration,fossil-fuelcombustion 0.15μg/m3(rollingthree-monthaverage);1.5μg/m3(quarterlyaverage) lossofbiodiversity,decreasedreproduction,neurologicalproblemsinvertebrates adverseeffectsuponmultiplebodilysystems;maycontributetolearningdisabilitieswhenyoungchildrenareexposed;cardiovasculareffectsinadults Thegaseouscriteriaairpollutantsofprimaryconcerninurbansettingsincludesulfurdioxide,nitrogendioxide,andcarbonmonoxide;theseareemitteddirectlyintotheairfromfossilfuelssuchasfueloil,gasoline,andnaturalgasthatareburnedinpowerplants,automobiles,andothercombustionsources.Ozone(akeycomponentofsmog)isalsoagaseouspollutant;itformsintheatmosphereviacomplexchemicalreactionsoccurringbetweennitrogendioxideandvariousvolatileorganiccompounds(e.g.,gasolinevapours). BritannicaExplores Earth'sTo-DoList Humanactionhastriggeredavastcascadeofenvironmentalproblemsthatnowthreatenthecontinuedabilityofbothnaturalandhumansystemstoflourish.Solvingthecriticalenvironmentalproblemsofglobalwarming,waterscarcity,pollution,andbiodiversitylossareperhapsthegreatestchallengesofthe21stcentury.Willwerisetomeetthem? Airbornesuspensionsofextremelysmallsolidorliquidparticlescalled“particulates”(e.g.,soot,dust,smokes,fumes,mists),especiallythoselessthan10micrometres(μm;millionthsofametre)insize,aresignificantairpollutantsbecauseoftheirveryharmfuleffectsonhumanhealth.Theyareemittedbyvariousindustrialprocesses,coal-oroil-burningpowerplants,residentialheatingsystems,andautomobiles.Leadfumes(airborneparticulateslessthan0.5μminsize)areparticularlytoxicandareanimportantpollutantofmanydieselfuels. Exceptforlead,criteriapollutantsareemittedinindustrializedcountriesatveryhighrates,typicallymeasuredinmillionsoftonsperyear.Allexceptozonearedischargeddirectlyintotheatmospherefromawidevarietyofsources.Theyareregulatedprimarilybyestablishingambientairqualitystandards,whicharemaximumacceptableconcentrationsofeachcriteriapollutantintheatmosphere,regardlessofitsorigin.Thesixcriteriapollutantsaredescribedinturnbelow. GetaBritannicaPremiumsubscriptionandgainaccesstoexclusivecontent. SubscribeNow