D ft P l f th P ti l t M ttDraft Proposal fortheParticulateMatter(PM) National Ambient Air QualityStandards (NAAQS)Briefing for Interagency ReviewJ ne 4 2012June 4,2012Washington, DCOverview of Briefing•Schedule• Current PM standards• Overview ofproosed decisionsp• Primary standards for fine particles• Primary standard for thoracic coarse particles• Secondary standards2ScheduleMajor MilestonesCompletion DateWorkshops on Key Policy-Relevant IssuesJul y 2007Integrated Review Plan FinalMarch 2008Integrated Science Assessment FinalDecember 2009Risk/Exposure AssessmentsPlansFinalFebruary 2009June/July 2010Policy Assessment Second DraftFinalJune 2010April 2011Proposed Rule SignedJune 7, 2012(court ordered)Final Rule SignedTBD3Current PM Standards•PMPrimary2.5– Annual standard with a level of15 μg/m3– 24-hour standard with a 98thpercentile form and a level of35μg/m3•PM10Primary–24-hour standard with a 1-expected-exceedance form and alevel of150 μg/m3Secondary•– Identical to primary PM2.5standards4Overview of Proposed Decisions• Fine Particles–PrimaryPM2.5Standards– Propose torevise annual standardlevel to 12 μg/m3 inconjunction with retaining 24-hour standard level at 35μg/m3• Thoracic Coarse Particles -PrimaryPM10Standard– Propose toretain the current standard•SecondaryPM2 5Standard2.5• Propose anew standarddefined in terms of a PM2.5visibility index, with an averaging time of 24 hours, a 90thpercentile form and a level of either 30 or 28 dvpercentile form,and a level of either 30 or 28 dv5Fine Particles:Significant Impacts on Public Health• Nationally,basedon PM2 5airqualityin 2005,weestimate:at o a y, based o2.5a qua ty 005, e est ate–Premature mortality:•130,000 - 320,000 excess deathsin adults• 5.4% of all deaths related to PM2.5exposures–Impacts among children:• 110,000 emergency department visits relatedto asthma (less than 18 years of age)• 200,000 cases of acute bronchitis (age 8-12)• 2,500,000 cases of exacerbation of asthma (age 6-18)–Impacts among adults:• 18,000,000 loss work days (age 18-65)• 180,000 heart attacks (age 17 and older)• 83,000 cases of chronic bronchitis (age 26 and older)• 62,000 hospitalizations for cardiovascular effects (age 17 and older)30 000 h it li ti f i t ff t ( ll )•30,000 hospitalizationsforrespiratoryeffects(allages)• In addition, recent research provides evidence thatdecreases in long-term PM2.5exposureshave beenassociated with an estimated increase in mean lifeexpectancyof approximately5 to 9 monthsyy6Fine Particles:Estimated National Impacts...Premature MortalityPercentage of total deaths due to PM2 5Percentage of total deaths due to PM2.5Krewski et al. (2009) PM mortality estimate<2.5%2.5 to 3.9%4 to 5%5.1 to 6.1%6.1 to 9%7Fine and Coarse Particles:Susceptible PopulationsP i d d b bli h l h i l di•Primarystandardsaretobesettoprotectpublichealth,includingsusceptible populations, with an “adequate margin of safety”•A variety of factors make people moresusceptible to PM-related healtheffects including:effects,including:– Pre-existing diseases (such as heartor lung disease, including asthma) orconditions (such as obesity)– Lifestage• Older adults• Children– Persons with lower socio-economic status (SES)•New evidence available in this reviewprovides stronger evidence for thispopulation• Emerging evidence for additional susceptible populations related to:– Genetic differences– Additional pre-existing diseases and conditions (such as diabetes)–Pregnancy, newborns8Fine Particles:History of the Primary PM2.5Standards•1997:Fine and coarse fractions of PM10considered separately;EPA set initial10p y;fine particle standards usingPM2.5as indicator•2006:Retained level of annual standard (15 μg/m3); revised level of 24-hourstandard (65 μg/m3lowered to 35 μg/m3)–Annual standard: Based level onlong-termexposure studies only (Harvard Six CitiesandAmerican Cancer Society (ACS)studies); keymorbiditystudies in children judged to be toouncertain a basis for establishing a lower level (e.g.,S. California Children’s Health Study)–24-hour standard: Based level onshort-termexposure studies only–CASAChad recommended revising annual standard level within a range of 13-14 μg/m3in–CASAChad recommended revising annual standard level within a range of 13-14 μg/mconjunction with revising 24-hour standard level within a range of 30-35 μg/m3; following final rule,CASACexpressed serious concerns with decision to retain annual PM2.5standard level•2009: US Court of Appeals, DC Circuit issued decisions on 2006 PM standardsConcluded “EPA failed adequately to explainin view of risks posed by shortterm exposures–Concluded “EPA failed adequately to explain why,in view of risks posed by short-term exposuresand the evidence of morbidity resulting from long-term exposures, itsannual standardis sufficienttoprotect public health with an adequate margin of safety”–Remandedannual standard for further consideration of whether it provides anadequatemargin of safety,especiallyinchildren and other susceptiblepopulationsy,ypp– Primary 24-hour PM2.5standard, as revised in 2006, was not challenged by litigants9Fine Particles:Overview of Health Effects EvidenceBased on ORD’sPM Integrated Science Assessment (ISA), which CASAC has endorsed:•Extensive new epidemiological evidenceis now available, including:– Extended analyses of seminal studies of long-term PM2.5exposures– Substantial increase in new U.S. multi-city, long- and short-term exposure studies– Additional types of evidence from controlled human exposure and animal toxicological studiesprovide support for effects observed in epidemiological studies•Compelling evidencesupports acausal relationshipbetween PM2.5andprematuremortalityandcardiovascular effects(long- and short-term exposures)• Additional evidence for a broad range of PM2.5-related health effects supports:Likely causal relationshipforrespiratory effects(longand shortterm exposures)–Likely causal relationshiprespiratory effects-and short-term exposures)–Suggestive of a causal relationshipfordevelopmental/reproductive effects, cancer(long-term exposures)• Evidence isnot sufficientto link health effects with anyspecific fine particlecomponent orgroupof componentsassociated with anysource categories of finegp pgparticles nor to exclude any component(s) from the mix of particles included in PM2.5indicator•No evidenceof adiscernible thresholdbelow which health effects would not occur10Fine Particles:Overview of Epidemiology EvidenceLong-termExposure “Cohort” Studies• Follows a specific group of study participants (“cohort”)over time and acrossurban areas;PM2.5concentrations over years are associated with specific health events (e.g.,deaths) across cities•Extended follow-upof important studies as well as new studies arelargely consistentwithprevious reports ofpremature mortalityat lower ambient PMconcentrations; provide stronger2.5concentrations; provide strongerevidence of morbidity effects• Studies of note include:–Extended analyses of ACSandHarvard Six Citystudies (premature mortality)–Extended analyses of S. California Children’s Health Study(decreased lungfunctiongrowth)yg g)–Women’s Health Initiative Study (WHI,cardiovascular-related mortality and morbidity effects observed inhealthy, post-menopausal women)–Medicare Air Pollution Study (MCAPS,premature mortality, older adults)Short-termExposure Studies• “Time-series studies” considergeneral populationor a subset (e.g., Medicareparticipants) in a single city or across multiple citiesover several years; dailychanges in PM2.5concentrations(one or more days) areassociated with daily changes inevents(e.g., deaths, hospitalizations)•New multicity studies greatly expandandreinforceevidence of mortality and morbidity effectsNew multi-city studies greatly expandreinforceevidence of mortality and morbidity effectsavailable in last review; studies of note include:–MCAPS(hospitalizations for cardiovascularand respiratory disease, older adults)–112 U.S. Cities study(premature mortality)11Fine Particles:Translating Evidence into Primary PM2.5Standards(1)•In translating evidence into basis for standard levels, we focus on epidemiologicalevidence:– Recognize health effects may occur over the full range of concentrations observed inepidemiological studies; there isno evidence of a discernible thresholdbelow which healtheffects would not occur–Controlled human exposure studies help to demonstrate causality but unlike in other recentControlled human exposure studieshelp to demonstrate causality but,unlike in other recentNAAQS reviews, are not helpful for setting the level of the PM2.5standards• Rely primarily on annual standard to provide protection from both long- and short-termPM2.5exposures, with 24-hour standard providing supplemental protection against highpeak concentrations– Considered most effective and efficient approach for providing public health protection– Supported by results from quantitative risk assessment•Annual standard level(see figure on next slide)g )– Focus on identifying levelssomewhat below long-termmean concentrationsreported inepidemiological studies (general approach used in previous reviews)– Considerbroader distribution of PM2.5concentrationsbeyond a point “somewhat below themean” to consider ranges of concentrations thatwere most influential ingenerating health effectestimates in epidemiological studies, as CASAC stronglyadvised us to do12Fine Particles:Translating Evidence into Primary PM2.5Standards(2)McConnell et al, 2003; Gauderman et al., 2004 (S CA CHS, 12 communities)Goss et al., 2004 (Cystic Fibrosis)Eftim et al., 2008 (MCAPS-ACS sites, 110 counties)Miller et al., 2007 (WHI, 36 cities)Causal / Likely Causal - Long-Term Exposure StudiesLong-term MeanPM2 5ConcentrationsLevel of current annual PM2.5standardDockery et al 1996; Raizenne et al 1996 (24 Cities StudyLipfert et al., 2006 (Veterans Study)Eftim et al., 2008 (MCAPS-Harvard Six Cities sites)Zeger et al., 2008 (MCAPS-East, 421 counties)Krewski et al., 2009 (ACS-Reanalysis II, 116 MSAs)McConnelletal,2003;Gaudermanetal.,2004(SCACHS,12communities)2.5(50thpercentiles)♦= long-term exposurestudies; causal or likelycausal relationship▲= short-term exposurestudies; causal or likelyZ b tti & S h t 2009 (112 iti )Bell et al., 2008 (MCAPS, 202 counties)Burnett et al., 2004 (12 Canadian Cities)Causal / Likely Causal - Short-Term Exposure StudiesLaden et al., 2006 (Harvard Six Cities)Dockeryetal.,1996;Raizenneetal.,1996(24-CitiesStudystudies; causal or likelycausal relationship■= long-term exposurestudies; suggestive of acausal relationshipDistributional StatisticsFranklin et al., 2008 (25 US cities)Klemm & Mason, 2003 (Harvard Six Cities)Dominici et al., 2006 (MCAPS, 204 counties)Burnett & Goldberg, 2003 (8 Canadian cities)Zanobetti&Schwartz,2009(112cities)25thpercentile10thpercentileof Health Event and/orStudy Population DataWoodruff et al., 2008 (infant mortality)Liu et al., 2007 (IUGR)Bell et al., 2007 (low birthweight)Suggestive - Long-Term Exposure StudiesFranklin et al., 2007 (27 US cities)Source: PolicyAssessment for theRe ie of the PM9 10 11 12 13 14 15 16 17Additional studies report effects at higher long-term meansMore limited and mixed evidence is available from single-city,short-term exposure studies with long-term mean PM2.5concentrations below 15 μg/m3Long –term mean PM2.5concentration (μg/m3)ReviewofthePMNAAQS, April 2011,Figure 2-813Fine Particles:Staff Conclusions in Final Policy AssessmentAnnual Standard 24-Hour Standard Potential Implications•Alternative suites of standardsmoststronglysupported byevidence12 to 11 μg/m335 μg/m3(retain current standard)g y pp y•Results in annual standard being thegenerally controlling standard, except inareas with particularly high peak-to-meanratios (e.g., Northwest)R lt i if bli h lth•Resultsinmoreuniformpublichealthprotection•More limited supportfor this suite ofstandards•Results in 24hour standard being theup to 13 μg/m3somewhat below 35 μg/m3,such as down to 30 μg/m3•Results in 24-hour standard being thecontrolling standard in a large number ofareas in many geographic regions•Results in more uneven public healthprotection14Fine Particles:CASAC AdviceAdequacy of Current Standards•CASACconcluded current standards are“not protective”and there are“significantpublic health consequences”at the current levels of the standard(s) that “justifyconsideration of lowering the PM2.5NAAQS further”Alternative Standards Appropriate to Consider•CASAC agreedwith staff’s approach to focus on annual standardCASACconcl ded that alternati eann al standard le elsithin a range of13 to 11•concluded that alternativeannual standard levelswithin a range of13 to 11μg/m3and24-hour standards levelswithin a range of35 to 30 μg/m3“aresupported by the epidemiological and toxicological evidence, as well as by the riskand air quality information”–Based on 2nddraft Policy Assessment, which did not include consideration ofanalyses of the broader distribution of PM2.5concentrations beyond a point“somewhat below the mean” to consider ranges of concentrations that were mostinfluential in generating health effect estimates in epidemiological studies15Fine Particles:Draft Proposal and ConsiderationsPropose torevise annual standard levelto12 μg/m3in conjunction withretaining 24-hour standard levelat35 μg/m3•Solicit comment on alternative annualstandard levels from 13 to 11 μg/m3Considerations: A focus on an annual standard level of 12 μg/m3:Placesgreatest weight on both longand shortterm exposure studiesproviding•greatest weight on both long-and short-term exposure studiesprovidingevidence of effects classified as having acausal or likely causal relationship–Below the lowest long-termmeanconcentrationsreported in all multi-city studies thatreported statistically significantassociations (i.e., below 12.8 μg/m3)• Placeslittle weighton more limited evidence from multi-city, long-term exposure studiesfor which we havesuggestive evidenceof a causal relationship for developmental effects• In conjunction with lowering the annual standard level to 12 μg/m3, the evidencemoststrongly supports retaining 24-hour standard levelat35 μg/m3strongly supports retaining 24-hour standard levelat35 μg/m– Changes in air quality designed to meet a lowerannual standard would likely result not only inlower annual average PM2.5concentrations but also in fewer and lower peak 24-hour PM2.5concentrationsTh dditi l t ti ld b id d b i d l t d d h th tii–Thus,additionalprotectionwould beprovided byarevisedannualstandardsuch thatrevsonto the 24-hour standard is not warranted16Fine Particles:Considerations(Continued)•Requesting comment onan annual standard level up to 13 μg/m3:– Places weight on most, but not all, multi-city studies; however, we have no basis forexcluding studies with long-term mean concentrations of 12.8 or 12.9 μg/m3– Placesno weighton considering the broader distribution of PM2.5concentrations downthrough which we continue tohave confidence in observed associations or on the morelimited evidence of serious effects in susceptible populations(e g infant mortality low birth(e.g.,infant mortality,low birthweight)– Placessubstantial weighton the remaininguncertainties and limitationsin the evidence– In conjunction with lowering the annual standard to 13 μg/m3,the evidence provideslimitedsupportfor alsoloweringthe 24-hour standard level– An annual standard of 13 μg/m3(absent a very low 24-hour standard level) could raiseissues similar to those which resulted in the remand of the 2006 PM2.5annual standard• Requesting comment on anannual standard level down to 11 μg/m3:–Placesgreater weighton considering therange of PM2 5concentrations below the long-Placesgreater weighton considering therange of PM2.5concentrations below the longterm mean concentrationsdown through which we continue to have confidence inobserved associations– Placesconsiderably more weight on limited evidence of serious effects in susceptiblepopulationsproviding evidencesuggestive of a causal relationshipPlacesless weighton the remaininguncertainties and limitationsin the evidence–less weighton the remaininguncertainties and limitationsin the evidence– In conjunction with lowering the annual standard level to 11 μg/m3, the evidencemoststrongly supports retaining 24-hour standard level17Costs and Benefits for Proposed Primary PM2.5Standards (12/35)•In setting NAAQS, EPA may notconsider implementation costs.PerExecutive Order 12866 and standardpractice EPA has conducted aProjected Costs and Benefits of Attainment of 12/35Incremental to Attainment of Current Standards in 2020*(Million 2006$, 7% Discount Rate)practice,EPA has conducted aRegulatory Impact Analysis forinformational purposes only.•Costs are lowbecause they considerfederal measures already in placeCosts$69Health Benefits $2,100 to $5,400including recently promulgatedregulations (e.g., CSAPR and MATS)and controls applied to meet the currentstandards (15/35).Net Benefits $2,000 to $5,300*E ti t d t d b fit dditi l t th i t d• Emission control measures wereapplied to sources of PM2.5, SO2, andNOx(few thousands of tons) formeeting proposed alternative*Estimatedcostsand benefitsareadditional tothoseassociatedwith meeting the current standards. Currently, we are performingQA on the cost and benefit estimates. A new version of the RIAwith updated estimates will be provided in the next few weeks.Weanticipatetherewillbean increasein thecosts;however,themeeting proposed alternativestandards (12/35).18e a c pa e e e be a c ease e cos s; o e e , ebenefits are still expected to significantly exceed the costs.Current and Projected PM2.5NonattainmentCurrent Standards Proposed Standards Proposed StandardsStandard(s)(15/35)NonattainmentAreas*p(12/35)**Estimated UsingRecent Air Qualityp(12/35)**Projected Considering‘On the Books’ Federal(2008-2010)by CountyControls (2020)by CountyBoth annual and24-hour standards16 14 8Annual standard only19 68 424-hour standard only16 21 6Total51 103 18*Nonattainment areas may include multiplecounties or onlya part of one county.**Estimated/projected conditions are for illustrativepurposes only. Assumingrevised PM NAAQS arepromulgated in June 2013,19pj pp y g p g ,designations would be based on 2011-2013 or 2012-2014 air quality data.2008-2010 PM2.5Concentrations byCountyProposed Standards: Annual NAAQS level = 12 μg/m3/24-hr NAAQS level = 35 μg/m320Note: This slide represents recent air quality conditions butnot necessarily the areas likelyto be designated as attainment/nonattainment. For illustrativepurposes, assuming revised PM NAAQS are promulgated inJune 2013, designations wouldbe based on 2011-2013 or 2012-2014 air quality data.2020 P j t d PMC t ti b C t ith ‘ th b k ’ F d l t l2020 Projected PM2.5Concentrationsby Countywith ‘onthebooks’ FederalcontrolsProposed Primary Standards: Annual NAAQS level = 12 μg/m3/24-hr NAAQS level = 35 μg/m321Projected design values indicate18 counties are likely not to meetone or both of theproposed primary PM2.5standards in 2020.Coarse Particles:History of the PM10Standard•1987:EPA first set PMstandards in order to protect against exposures to particles10that can penetrate deeply into the respiratory system– 24-hour standard: Form set at one-expected-exceedance and level set at 150 μg/m3– Annual standard: Level set at 50 μg/m3•1997:Given newly established fine particle standards,purpose of PM10standardsbecame toprotect againstthe coarse fraction of PM10(i.e.,PM10-2.5)– Following litigation, the 1987 PM10standards remained in place2006:EPA retained the 24hour standard and revoked the annual standard•-– Decision on annual standard based on insufficient evidence linking health problems tolong-term exposure to inhalable coarse particle pollution– In subsequent litigation, DC Circuit courtupheld decisions and supporting rationale forPMd d10standard•Today’s 24-hour PM10standard is the same as that set in 198722Coarse Particles:ISA Conclusions•Causality:The available evidence is“suggestive”of acausal relationship between short-term thoracic coarseparticle exposures and mortality, respiratory effects, anddi l ff tcardiovasculareffects– “Suggestive,” rather than “causal” or“likely causal”, reflects thegreater degree of uncertaintyassociated with the healthevidence for PM10-2.5•Composition:Evidence is not sufficient to link health effectswith specific sources or components of PM10-2.5(such asf )those typical ourban versus rural areas)23Coarse Particles:Health Evidence•In epidemiologic studies,associations between PM102 5and mortality/morbidity-2.5and mortality/morbiditywere generally positive, with some being statistically significant– In the subset of studies that employed co-pollutant models to evaluate the potential forconfounding, PM10-2.5effect estimates remained positive, and in a few cases statisticallysignificant• Single-city analyses reportedpositive and statistically significant associationsina fewurban locations that would have met the current PM10standardduring thestudy period– Detroit (Ito et al., 2003)T t (Li t l 2002)–Toronto(Linetal.,2002)– Birmingham, Chicago, Pittsburgh (ISA,based on Zanobetti and Schwartz, 2009)• A few recentdust storm studieshave reported associations between mortality ormorbidityand PM of non-urban,crustal origing– Associations were positive withsome being statistically significant– Mostly non-U.S. studies– PM10concentrations in these study locations likely well above those allowed by thecurrent PM10standard24Coarse Particles:Uncertainties and Limitations•Extent to which thoracic coarse particles themselves, rather than one or more cooccurring pollutantsare responsible for health effectsreported in epidemiologicoccurring pollutants,studies– Relatively small number of studies that have evaluated co-pollutant models and supportingexperimental studies•Extent to which PM102 5concentrationsmeasured at central-site monitorsreflectExtent to which PM10-2.5concentrationsmeasured at centralsite monitorsreflectexposures in study populations– Relatively limited spatial coverage provided by existing PM10-2.5monitors combined with therelatively large spatialvariability in ambient PM10-2.5concentrations– Tends to decrease the likelihoodthat an association between PM10-2.5and health effects wouldb d d if h i i ibedetected,evenifsuchanassociationexists• Measurements of coarse particle concentrations at which reported health effects occur– Given the lack of a national monitoring network for PM10-2.5, different health studies have useddifferent approaches to estimateor measure thoracic coarse particles and it is not clear howthese different methods relate to each other• Extent to which coarse particle composition affects particle toxicity– Lack of information on PM10-2.5composition makes it difficult to characterize the variability inhealth effect associations with thoracic coarse particlesL k f tit ti ti t f PMi t d h lth i k•Lackofquantitativeestimatesof PM10-2.5-associated healthrisks– Evidence judged insufficientto support quantitative risk assessment, adding to uncertaintyregarding potential public health implications of retaining versusrevising the current standard25Coarse Particles: Staff and CASAC Conclusions on theCurrent Standard•Staff conclusionin Policy Assessment:Consider eitherretaining or revisingthe current standard, depending on the weight placed on the evidence and itsassociated uncertaintiesRetain:Focuses on the“suggestive”nature of the PMhealth evidence–Retain:Focuses on thesuggestivenature of the PM10-2.5health evidence–Revise:Placesmore weight on the results of specific studies, particularly thosereporting associations with PM10-2.5in locations that would have met the current PM10standard, andless weighton the“suggestive”nature of the evidence•CASAC concludedthat the available evidence, while limited, is sufficient tocallinto questionthe level of protection provided bythe current standard– CASAC placed weight on studies reporting associations with PM10-2.5in locations thatld h t th t PMt d d lt fll t t d l dwould havemet thecurrent PM10standard,resultsfromco-pollutantmodels,andcontrolled human exposure studies– CASACdid not discussthe role that the“suggestive” nature of the evidenceplayed in reaching their conclusion on the adequacy of the current standard26Coarse Particles:Staff Conclusions on Potential AlternativeStandards•Final Policy Assessment:Appropriate toconsider revising the formand thelevel•Form: 98thpercentileof the annual distribution of 24-hour PM10concentrations, averagedover 3 years– Based on analyses in the final Policy Assessment, a98thpercentile formcouldbetter targetpublic health protectionto locations with higher coarse particle concentrations and to locationswhere we have more confidence in associations with health effects and...–Could beless influenced byrelativelyrare eventsthat can result in high PM10concentrationsy yon a small number of days in ayear•Level: 85 μg/m3to 65 μg/m3, with the upper end of the range supported by the strongesthealth evidence–98thpercentile 24-hour PM10concentrations in U S study locations wereabove 85μg/m3in98percentile 24hour PM10concentrations in U.S.study locations wereabove 85μg/minlocations where positive and statistically significant PM10-2.5effect estimates have been reported– Based on analyses in the final Policy Assessment, standard levels from85 μg/m3to just above75 μg/m3could be considered“generally equivalent” to the current PM10standard–Even such“generallyequivalent” standard levelscouldbetter targetublic healthyqpprotection, compared to the current standard27Coarse Particles:CASAC Conclusions and Recommendationson Potential Alternative Standards• CASAC recommendations are based on the 2nddraft Policy Assessment, which did notinclude the analyses of targeting public health protection– These analyses were conducted in response toCASAC comments and were included in thefinal PolicyAssessment•Form: CASAC “strongly” recommendedrevising the form to the98thpercentile•Level: CASAC agreedthat standard levels from85(a level that could be “generallyi l t” t t t d d)t 65 /3ld b j tifi dh thequivalent” tocurrentstandard)to65μg/m3could bejustified;however,theyrecommendedsetting the level in the range of75 to 65 μg/m3– CASAC recommended revising toincrease public health protection• CASAC concluded that a level at or below 75 μg/m3would result in increased publich lth t ti th U ShealthprotectionacrosstheU.S.– CASAC noted that margin of safetyconsiderations could justify a PM10standard level at orbelow 75 μg/m328Coarse Particles:Draft Proposal and ConsiderationsPropose to retainthe current standardIn addition, in light of CASAC’s recommendations, the draft proposal welcomes thepublic’s views on different approaches to considering and accounting for the evidence andits limitations and uncertainties, as well as on the appropriateness of revising the PM10primary standardC id tiConsiderations• Retaining the current standard placesa large amount of weight on theISAconclusionsthat the evidence is only“suggestive”of a causal relationship– We conclude that “suggestive” evidence issufficient to justify retaining the currentt d d b t t ffi i t t j tif i i th t t d dstandard butnotsufficient tojustifyrevising thatstandard• In contrast to CASAC, our rationale places relativelymore weighton the“suggestive”nature of the overall body of evidence in interpreting specific studies•CASAC placed more weight on specific studies than we judge to beappropriate• Given the “suggestive” nature of the evidence, there issubstantial uncertaintyinthe extent to whichadditional public health benefitswould result, beyond thoseprovided bythe current standard, if we set revised standard that targets protectionto different areas29Secondary Standards:History of Visibility Standards• Over time, NAAQS and Regional Haze Programs have worked together•NAAQS: CAA requires “secondary standardswhich, in the judgment of theAdministrator” are “requisite to protect the public welfare from any known oranticipated adverse effects (welfare effects explicitly include visibility)–1971: Secondary PM NAAQS set to protect visibility at airports; distinct and more stringentthan primary standard–1987: Secondary NAAQS set identical to new primary PM10standards; solicited commenton approaches to setting a distinct secondary standard–1997: Secondary NAAQS set identical to new primary PM2 5standards; intended to2.5standards; intended toaddress urban visibility impairment in conjunction with Regional Haze Program•Regional Haze Program:–1977: Congress established a national visibility goal to “remedy existing impairment andt f t i i t” i Cl Iprevent futureimpairment” inClassIareas–1990: Clean Air Act Amendments emphasizedregional haze issues and directed EPA toestablish Grand Canyon Visibility Transport Commission–1999: Regional Haze Rule promulgated;specified use of an equation for calculatingisibilit impairment (in terms of light e tinction) as a f nction of PM components andvisibility impairment (in terms of light extinction) as a function of PM components andrelative humidity30Secondary Standards:History of Visibility Standards(cont.)•2006 NAAQS: Secondary standards set identical to revised primary PM2.5standards–Not consistent withstaff andCASAC adviceto consider distinct sub-dailysecondary standard– CASAC expressed serious concerns with final decision; continuing to rely onprimary standards to protect against welfare effects “assures neglect, and willallow substantial continued degradation, ofvisual air quality over large areas ofthe country”•Court remand: Decision to set secondary standards identical to primarystandards wasunreasonable and contrary to the law– EPA failed to identify a target levelof protection, as required by CAAEPA k l d d th t PMb d t d d ith 24h i–EPAacknowledged thataPM2.5mass-basedstandard,witha24-houraveragingtime, would not address regional differencesin relative humidity, yet EPA did notaddress this issue at all in final decision31Secondary Standards:Key Visibility Science from the ISA•Publicpercetionof haze depends onlightinandscene characteristicsas well aspgonlight extinction(i.e., fractional loss of light per unit distance)•Good visibility is important to public welfare– Air quality impacts on visibility negatively affect a person’s sense of personal comfort andwellbeing– For a given scene and lighting conditions, people consistently rate visibility levels and identifythe amount of haze that is unacceptable whenviewing photographs within a range of visibilityconditions from pristine to highly impaired• ISA concluded there is acausal associationbetween PM and light extinction– Particle light extinction efficiencydepends on particle size and composition– There is no consistent relationship between PM2.5mass concentration and light extinction• Determining PM2.5light extinction–Directly measureby optical instrumentation, butno Federal Reference Method (FRM)currently availableCl li i l if i l il bl bi PM–acuateusingasimpleequationfromroutinelyavailableambientPM2.5massconcentration/composition and relative humidity data (as done for the Regional Haze Program)32Secondary Standards:Urban-Focused Visibility Assessment•Urban visibility preference survey studiesconducted in four areas: Denver, CO;V BC Ph i AZ d W hi t DCVancouver,BC;Phoenix,AZ;and Washington,DC– Survey participants for each urban area consistently identified levels ofunacceptable visibility– Results showed a range of values that dividevisibility into acceptable and unacceptableconditions, results varied depending on characteristics of selected urban scene (using a“deciview”(dv) scale to characterize visibility)deciview (dv) scale to characterize visibility)• Low end of the range – 20 dv(based on Denver study)• Middle of the range – 25dv (based on Phoenix study)• High end of the range – 30 dv(based on Washington, DC study)– These values define threetarget protection levelsused in subsequent assessments• Highest haze levels were observed for Eastern U.S. and California urban areas– Worst haze conditions were generally caused by sulfate, nitrate and carbonaceous PM2.5• Assessed visibility impairment associated with just meeting the current PM2.5standardsfor 14 urban areas– Target protection levels exceeded in most urban study areas– Resulted insubstantially uneven visibility protection (i.e., significantover protection inWest to get adequate protection in East)•Estimated improvements in visibility associated with alternative standards based onPM-related light extinction; resulted inuniform protectionacross all urban areas33Secondary Standards:Staff and CASAC Conclusions onAdequacy of Current StandardsI h P li A ff l d d l il bl i f il l•InthePolicy Assessment,staffconcludedcurrentlyavailableinformationcearycalls into question the adequacy of the current suite of PM2.5standardsin thecontext of public welfare protection from visibility impairment, primarily in urbanareasL t f d d t t t ti l l if ll t th t it–Largepercentageof daysexceed targetprotectionlevelsifallareasmet thecurrentsuiteof PM2.5standards– Current averaging times (24-hours and annual) are not well-suited to protect against PMrelated visibility impairment•Current averaging times include nighttime conditions for which the science neededCurrent averaging times include nighttime conditions,for which the science neededto support identification of appropriate levels of visibility protection is not welldeveloped or understood•CASAC concurred, concluding that:“ t d PM t d di d t t t t i ibilitth il l“currentsecondary PMstandardsareinadequatetoprotectvisibility,astheirevesare too high, their averaging times aretoo long, and their (dried) mass-basedindicators do not fully represent PM effects on visual air quality in the ambientatmosphere”34Secondary Standards: Staff and CASAC Conclusions onAlternative StandardsAl i i diAlternativeindicators:•Directly measured PM2.5light extinction– while strongly supported by CASAC for the futuredevelopment of Federal Reference Method would take several years•Calculated PM2.5light extinction– preferred alternative for this review -- build on existing monitoringnetwork and calculate light extinction similar to Regional Haze ProgramAlternative averaging times:• In draft PA, staff concluded, and CASAC concurred, that 1-hour averaging time was appropriate(limited to daylight hours with relative humidity less than 90%); also recognized that up to 4-houraveraging time may be appropriate• Final PA concludes that a24-hour averaging timeis a reasonable and appropriate surrogate for lightextinction calculated on a sub-daily basis– Based on recent analyses that identified data quality concerns with some hourly PM2.5data–Also approriate to consider a4-hour averagintimeto the extent that dataqualitissues can bepgyappropriatelyaddressedLevel and form:• Final PA concludes that consideration should be given to the upper part of the range of levelspresented in the draft PA, and supported by CASAC, especially in light of the limited nature of theinformation available fromthe public preference studies– Range from 28 – 25 dv, in conjunctionwith a 24-hour averaging time and 90thpercentile form– Range from 30 – 25 dv, in conjunctionwith a 4-hour averaging time and 90thpercentile form35Secondary Standards:Draft Proposal•With regard to current standards:– Propose that the existing PM2.5standards arenot adequately protective norappropriate to address PM-related visibility impairment– Propose thata new standard is warrantedto provide increased protection,primarily in urban areas in conjunction with the Regional Haze Program toprimarily in urban areas,in conjunction with the Regional Haze Program,toachieve appropriate protection in areas across the country• With regard to a new standard to address PM-related visibility impairment(and respond to the court’s remand):p )–Proposea new standard defined in terms of aPM2.5visibility indexwith anaveraging time of 24 hours, a90thpercentile form(averaged over 3 years),and alevel of either 30 or 28 dv• Solicit comment on a range of levels down to 25 dv• Also solicit comment on alternative standards to address PM-related visibilityimpairment, including a sub-daily averaging time (e.g., 4 hours) and associatedalternative levels in the range of 30 to 25 dv36