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The updated WHO Global Air Quality Guidelines (AQGs) provide recommendations on air quality guideline levels as well as interim targets for ... Home/ Newsroom/ Questionsandanswers/ item/ WHOGlobalAirQualityGuidelines WHOGlobalAirQualityGuidelines 22September2021|Q&A TheupdatedWHOGlobalAirQualityGuidelines(AQGs)providerecommendationsonairqualityguidelinelevelsaswellasinterimtargetsforsixkeyairpollutants.Theyalsoofferqualitativestatementsongoodpracticesforthemanagementofcertaintypesofparticulatematter(PM),forexample,blackcarbon/elementalcarbon,ultrafineparticles,andparticlesoriginatingfromsandandduststorms,forwhichthereisinsufficientquantitativeevidencetoderiveAQGlevels. WhataretheWHOGlobalAirQualityGuidelines? TheupdatedWHOGlobalAirQualityGuidelines(AQGs)providerecommendationsonairqualityguidelinelevelsaswellasinterimtargetsforsixkeyairpollutants.Theyalsoofferqualitativestatementsongoodpracticesforthemanagementofcertaintypesofparticulatematter(PM),forexample,blackcarbon/elementalcarbon,ultrafineparticles,andparticlesoriginatingfromsandandduststorms,forwhichthereisinsufficientquantitativeevidencetoderiveAQGlevels.Basedontheextensivescientificevidencecurrentlyavailable,theguidelinesidentifythelevelsofairqualitynecessarytoprotectpublichealthworldwide.TheAQGsalsoserveasareferenceforassessingif,andbyhowmuch,theexposureofapopulationexceedslevelsatwhichitmightcausehealthconcerns.Theycoversomeofthemostmonitoredpollutantscriticalforhealth,forwhichevidenceonhealtheffectsfromexposurehasadvancedthemostinthepast15years.Theguidelinesfocusonso-calledclassicalpollutants,particulatematter(PM₂.₅andPM₁₀),ozone(O₃),nitrogendioxide(NO₂),sulfurdioxide(SO₂)andcarbonmonoxide(CO).Whenactionistakentoreducetheseclassicalpollutantsitalsohasanimpactonotherpollutants.Guidelinelevelsforspecifiedpollutantscanbeusedasanevidence-informedreferencetohelpdecision-makersinsettinglegallybindingstandardsandgoalsforairqualitymanagementatinternational,nationalandlocallevels.Theyarealsoapracticalinstrumentwithwhichtodesigneffectivemeasurestoachievepollutantemissionandconcentrationreductions,andtherefore,toprotecthumanhealth.WHOperiodicallyissuesthesehealth-basedAQGstoassistgovernmentsandcivilsocietyinreducinghumanexposuretoairpollutionanditsadverseeffects. Whatisnewintheseguidelines?  Sincethelast2005globalupdate,therehasbeenamarkedincreaseinthequalityandquantityofevidencethatshowshowairpollutionaffectsdifferentaspectsofhealth.Forthatreason,andafterasystematicreviewoftheaccumulatedevidence,several oftheupdatedAQGvaluesarenowlowerthan15yearsago.Therearealsonowclearerinsightsaboutsourcesofemissionsandthecontributionofairpollutantstotheglobalburdenofdisease.Recommended2021AQGlevelscomparedto2005airqualityguidelines.µg=microgramᵃ99thpercentile(i.e.3–4exceedancedaysperyear).ᵇAverageofdailymaximum8-hourmeanO₃concentrationinthesixconsecutivemonthswiththehighestsix-monthrunning-averageO₃concentration.Note:Annualandpeakseasonislong-termexposure,while24hourand8hourisshort-termexposure.ComparedtopreviousWHOguidelines,thenewAQGs:usenewmethodsforevidencesynthesisandguidelinedevelopment;reinforceevidenceonhealtheffects;providehighercertaintyintheevidenceofhealtheffectsoccurringatlowerlevelsthanpreviouslyunderstood;offeradditionalAQGlevels,suchasforpeakseasonO₃and24-hourNO₂andCO,aswellassomenewinterimtargets;offernewgoodpracticestatementsonthemanagementofcertaintypesofPM(i.e.blackcarbon/elementalcarbon,ultrafineparticles,andparticlesoriginatingfromsandandduststorms).  Whatisairpollutionandwherearethesepollutantsfoundindailylife? Airpollutionisthecontaminationoftheairwebreathe,indoorsoroutdoors,byanychemical,physicalorbiologicalagentthatispotentiallythreateningtohumanandecosystemhealth.Thepollutantswiththemostrobustevidenceforpublichealth concernincludeparticulatematter(PM),ozone(O₃),nitrogendioxide(NO₂)andsulfurdioxide(SO₂)andcarbonmonoxide(CO).ThehealthrisksassociatedwithPMsmallerthanorequalto2.5microns(µm)indiameter(PM₂.₅)areofparticular publichealthrelevance.PM₂.₅andPM₁₀arecapableofpenetratingdeepintothelungsandPM₂.₅canevenenterthebloodstream,primarilyresultingincardiovascularandrespiratoryimpacts.In2013,outdoorairpollutionandPMwereclassifiedas carcinogenicbyWHO’sInternationalAgencyforResearchonCancer(IARC).Airpollutionoriginatesfromnumeroussourcesofemission,bothnaturalandanthropogenic(resultingfromhumanactivity).Themainsourcesofanthropogenicairpollutioncanvarygeographically,butincludetheenergysector,thetransportsector,domesticcookingandheating,wastedumpsites,andindustrialactivitiesandagriculture.Theprocessofcombustionisthegreatestcontributortoairpollution,inparticulartheinefficientcombustionoffossilfuelsandbiomasstogenerateenergy.Inindoorenvironments,theuseofsolidfuelsandkeroseneinunventedheatingandcookingstoves,tobaccocombustionandcombustionforotherpurposes,suchasculturalorreligiouspractices,areimportantaswell. HowweretherecommendedAQGlevelsdetermined? ThedevelopmentofWHOguidelinesadherestoarigorousprocessofreviewingandevaluatingevidence,andinvolvesseveralgroupsofexpertswithwell-definedroles.Aguidelinedevelopmentgroupdefinesthescopeandkeyquestionsoftheguidelines, anddevelopstherecommendations,basedonthedistilledevidenceprovidedbythesystematicreviewteam.Inaddition,anexternalreviewgroupprovidesvaluablecomments,whiletheWHOsteeringgroup,composedofWHOstafffromallregions,oversees implementationoftheproject.FortheAQGs,morethan500paperswereidentifiedforsystematicreviewandsynthetizedtogetthemostup-to-dateevidenceforestablishingthenewAQGlevels.Theseguidelinesdonotincluderecommendationsaboutanykindofmultipleexposures.Ineverydaylife,peopleareoftenexposedtoamixtureofairpollutantsatthesametime.WHOacknowledgestheneedtodevelopcomprehensivemodelstoquantifytheeffectsofmultipleexposuresonhumanhealth.However,asthemainbodyofevidenceonairqualityandhealthstillfocusesontheimpactofsingleairpollutantsonhealthoutcomes,thecurrentguidelinesproviderecommendationsforeachairpollutantindividually. WhyaretheAQGssoimportantforprotectinghealth? Theburdenofdiseaseassociatedwithbothambientandhouseholdairpollutionexposureislargeandgrowing.Thisispartlyduetoincreasesinexposuresinlow-andmiddle-incomecountries,butinpartalsoduetotherapidlyincreasingprevalenceof noncommunicablediseases(NCDs)worldwideasaresultofpopulationageingandlifestylechanges.Airpollutionespeciallyincreasesmorbidityandmortalityfromthenoncommunicablecardiovascularandrespiratorydiseasesthatarethemajorcauses ofglobalmortality;italsoincreasesthediseaseburdenfromlowerrespiratorytractinfectionsandincreasespretermbirthandothercausesofdeathinchildrenandinfants,whichremainamajorcauseofthediseaseburdeninlow-andmiddle-income countries.WHOestimatesshowthataround7millionprematuredeaths,mainlyfromnoncommunicablediseases,areattributabletothejointeffectsofambientandhouseholdairpollution.Globalassessmentsofambientairpollutionalonesuggesthundredsofmillionsofhealthyyearsoflifelost,withthegreatestattributablediseaseburdenseeninlowandmiddle-incomecountries.Althoughairqualityhasimprovedgraduallyinhigh-incomecountries,pollutantconcentrationsstillexceedthe2005WHOAQGsforseveralpollutantsinmanyareas.Morethan90%oftheglobalpopulationin2019livedinareaswhereconcentrationsexceededthe2005WHOairqualityguidelineforlong-termexposuretoPM₂.₅.Airqualityhasgenerallydeterioratedinmostlow-andmiddle-incomecountries,becauseoflarge-scaleurbanizationandeconomicdevelopmentthathaslargelyreliedontheinefficientcombustionoffossilfuels,likecoal,aswellasinefficientresidentialfueluseandindustry.However,disparitiesinairpollutionexposureareincreasingworldwide,particularlyaslow-andmiddle-incomecountriesareexperiencinggrowinglevelsofairpollution. Howistheburdenofpoorairqualitydistributedglobally? Exposuretoairpollutantsisheavilydependentontheirambientconcentrations.Forexample,ambientPM₂.₅concentrationsvarysubstantiallybetweenandwithinregionsoftheworld.Importantly,morethan90%oftheglobalpopulationin2019livedin areaswhereconcentrationsexceedthe2005WHOAQGlevelof10µg/m³–andwiththe2021AQGlevelbeinglowertherewillsubsequentlybeanincreaseintheattributablehealthburdeninallcountries.In2019,annualpopulation-weighted PM₂.₅concentrationswerehighestintheWHOSouth-EastAsiaRegionandthenintheEasternMediterraneanRegion.ElevatedconcentrationswerealsoobservedinsomewesternAfricancountries,largelyduetotheimpactofSaharandust.Windblowndesert dustcontributestosometimesveryhighexposurestoparticleslargerthan10µm.ThisisaprominentissueinmanyaridareasintheMiddleEast,northernAfrica,theGobiDesertandelsewhere..ManyofthecountrieswiththelowestnationalPM₂.₅exposurelevelswereeitherintheWHORegionoftheAmericasortheEuropeanRegion.TrendsinPM₂.₅indicatearelativelystablepopulation-weightedglobalmeanconcentration,whichreflectsboth decreasesinexposureintheEuropeanRegion,theAmericasandrecentlyinsomepartsoftheWesternPacificRegion,andincreaseselsewhere. Howcantheseguidelinesbeused? TheAQGsproviderobustevidence-informedguidancetoprotectpublichealthfromairpollution.Whereasguidelinesarenotlegallybindingrecommendations,theycanbeusedasanevidence-informedreferencetooltohelpdecision-makersinsetting legallybindingstandardsandgoalsforairqualitymanagementatinternational,nationalandlocallevel.Academicresearchersandnationalandlocalauthoritiesworkinginthebroadfieldofairpollutionmayalsofindthemusefulforplanning andimpactassessments,andtheymaystimulatefurtherresearchandmonitoring.Theycanalsobeusedasanadvocacytoolforprotectingpublichealthfromairpollution,forexamplebycivilsocietyandacademicgroups. WhatisthedifferencebetweenAQGlevels,interimtargetsandgoodpracticestatements? The AQGlevels provideevidence-informedquantitativerecommendations,basedonsystematicreviewoftheevidenceofadversehealtheffects(includinganindicationoftheshapeoftheconcentration–responsefunction) forPM₂.₅,PM₁₀,NO₂,O₃,SO₂andCO,forrelevantaveragingtimesandinrelationtocriticalhealthoutcomes.Interimtargets servetoguidereductioneffortstowardstheultimateandtimelyachievementoftheAQGlevels.Meetingtheinterimtargetsmayhaveanotablebenefitforhealth,especiallyinthoseregionswhereexposuresfarexceedinterimtargets.Goodpracticestatements helptomanagecertaintypesofparticulatematter(i.e.blackcarbon/elementalcarbon,ultrafineparticles,andparticlesoriginatingfromsandandduststorms),whennumericalAQGlevelscannotbeestablishedintheabsenceofclearquantitative evidenceonindependenthealtheffectsfromthesepollutants. HowmanylivescouldbesavedorimprovedifcountriesachievenewAQGlevels? AchievingtherecommendedAQGlevelswilldeliversubstantialhealthbenefitsglobally.WHOhasperformedarapidscenarioanalysistoassessthehealthgainsattributabletoimprovedannualambientparticulatematterconcentrations,iftheAQGlevels wereachieved.Around80%ofdeathsattributedtoPM₂.₅exposureintheworldcouldbeavoidedifcountriesattaintheannualAQGlevelforPM₂.₅.Reachingtheinterimtargetsalsoofferssubstantialbenefitsforhealth.Forexample,attainment ofinterimtarget4forPM₂.₅(thesamelevelastheAQGfrom2005),wouldresultinanearly48%decreaseintotaldeathsattributedtoPM₂.₅exposure.ThehighestimpactwouldbeobservedintheSouth-EastAsiaandAfricanregions(57%and60% reductionrespectively).Resultsclearlydemonstrateamajorreductionintheestimatedburdenofdisease,evenifotheranalysesmayyielddifferentestimatesduetodifferentassumptionsmade.TheWHOscenarioanalysisshowedthatiftheinterimtargetswereachieved,thegreatestbenefitintermsofreducedburdenofdiseasewouldbeobservedincountrieswithhighPM₂.₅concentrationsandwithlargepopulations.Resultsaresignificantlydifferentforhigh-incomecountries,asinmostcasesthePM₂.₅ambientconcentrationsintheseareasarealreadybelowtheinterimtargets. IstherealinkbetweenairqualityandCOVID-19? Poorairqualityisanimportantriskfactorforbothacute(e.g.pneumonia)andchronicrespiratoryandcardiovasculardiseases(suchaschronicobstructivepulmonarydiseaseorstroke).PeoplewithunderlyingmedicalconditionsarethoughttobeatagreaterriskofdevelopingseverediseasefromCOVID-19infection;thus,airpollutionismostlikelyacontributingfactortothehealthburdencausedbyCOVID-19.DuringtheglobalCOVID-19pandemic,however,therehasbeenanimportant,albeitshort-term,reductioninconcentrationsofairpollutantsacrosscities.Thisreductionwasmoreprominentinthecaseofnitrogenoxides(NOₓ),apollutantverymuchrelatedtotraffic,whichwasdramaticallycurtailedbylockdownmeasures.Europeandataforsomecitieshasshownareductionofaround50%,andinsomecasesupto70%,inNO₂levelscomparedtopre-lockdownvalues.COVID-19hasbeenatragedybut,atthesametime,theresponsemeasureshaveshownhowpoliciesrelatedtotransportandthewaypeoplework,studyandconsume,cancontributetoabetterairquality,somethingthatshouldbetakenintoconsiderationforthepost-pandemicrecoverypoliciesthatmanycountriesarealreadyworkingon. Howdoesreducingairpollutionalsosupportclimateaction? Someairpollutants–particularlyblackcarbon(acomponentofPM)andtropospheric(ground-level)ozone–arealsoshort-livedclimatepollutants,whicharelinkedwithbothhealtheffectsandnear-termwarmingoftheplanet.Theypersistintheatmosphereforaslittleasafewdaysormonthsandtheirreductionhasco-benefitsnotjustforhealthbutalsofortheclimate.Almostalleffortstoimproveairqualitycanenhanceclimatechangemitigation,andclimatechangemitigationeffortscan,inturn,improveairquality.Notably,reductionorphase-outoffossilandbiomassfuelcombustionwillreducegreenhousegasemissionsaswellashealthrelevantairpollutants.Bypromotingenvironmentalsustainabilityhandinhandwithpublichealthprotection,wecanmakelargestepstowardsmitigatingclimatechangeandachievingtheSustainableDevelopmentGoals. WHOTEAM Environment,ClimateChangeandHealth News NewWHOGlobalAirQualityGuidelinesaimtosavemillionsoflivesfromairpollution 22September2021 Factsheets Ambient(outdoor)airpollution 22September2021 SubscribetotheWHOnewsletter→