Traffic- Related Air Pollution:A Critical Review of the Literature on Emissions,Exposure, and Health EffectsClean Air Act Advisory CommitteeCrystal City, VAOctober 6 – 7, 2009Dan Greenbaum, PresidentHealth Effects InstituteGoals of the ReviewSummarize and synthesize relevant information onair pollution from traffic and its health effects, linking:•Emissionsandexposure to traffic air pollution•Exposure to traffic air pollutionandhealth effects•Toxicological dataandepidemiologic associationsA preprint of the report was released in May 2009The final Report, following extensive QA/QC, will bepublished in fall 2009HEI Traffic Review PanelIra Tager—UC Berkeley,ChairKenneth Demerjian—SUNY, AlbanyMark Frampton—U RochesterMichael Jerrett—UC BerkeleyFrank Kelly—King’s CollegeLester Kobzik—Harvard SPHNino Künzli—IMdM, BarcelonaBrian Leaderer—Yale SPHThomas Lumley—U of Washington SPHFrederick Lurmann—Sonoma Tech. IncSylvia Richardson—Imperial CollegeJon Samet—Johns HopkinsMichael Walsh—ConsultantEmissions from Motor VehiclesThe Current ContextSignificant progresshas beenmade in reduction of pollutantemissions from motor vehiclesdespite increases in number ofvehicles and vehicle milestraveledIncreased urbanization andurban populations have:•Increased dependenceon motor vehicles andtraffic congestion•Changed land usepatterns such thatmore people are neartraffic sources ofpollutionReport OrganizationThere are many studies(over 400) that haveattempted to look attraffic exposure andeffects•However, they are notallof equal quality1. How should weassessExposure?•Who is likely to be exposed?•What exposure assessment methods used inepidemiologic studies?•Pollutant surrogates for traffic exposures (e.g., NO2, EC/BS,CO, UFPM, benzene, etc.)•Distance from and/or length of roadways•Estimate of traffic density or intensity•Modeling of primary traffic-generated pollutant exposureVOC (TraceAir) Distance Decay Around Highway 401, Toronto0.00.10.20.30.40.50.60.70.80.91.0-1000 -800 -600 -400 -200 0 200 400 600Distance from Expressway (m)

Standardized VOC LevelsBenzene (TraceAir)THC (TraceAir)NO2 (Ogawa)Who is Likely to be Exposed?Highest levels within 300 – 500 meters of a major roadToronto, Beckerman et al. (2008)Near Roadway Exposure Can Include Large PopulationsToronto Example: ~45%(within 500 meters of an expressway; 100 meters of a major road)Los Angeles Example: (~44%)Portland, Oregon ~37%What Markers or Surrogates?•Pollutant surrogates for traffic exposures (e.g.,NO2, EC/BS, CO, UFPM, benzene, etc.)•Criteria for what is a good surrogate:1.Traffic as the major source2.Emissions vary with other motor vehicle constituents3.Can be measured at low concentrations by reasonablyinexpensive and accurate methods4.Not have independent health effectsNO2as a surrogate•There is substantialvariability in averageconcentrations bylocations.•NO2 is a potentialsurrogate for vehicleemissions if it is measuredon a fine spatial resolution.PM2.5as a Surrogate•Use of PM2.5as asurrogate is of limitedvalue because manysources contribute tourban PM2.5and PM2.5concentrations are wellmixed within a region•Current centralmonitors do not providesufficient spatialresolution for assessingthe contribution oftraffic to ambient PM2.5What Markers or Surrogates?•Pollutant surrogates for traffic exposures (e.g.,NO2, EC/BS, CO, UFPM, benzene, etc.)•Criteria for what is a good surrogate:1.Traffic as the major source2.Emissions vary with other motor vehicle constituents3.Can be measured at low concentrations by reasonablyinexpensive and accurate methods4.Not have independent health effects•Can provide useful information but nonemeet all these criteria...Can We Use Exposure Models?Models used•Proximity models•Geostatisticalinterpolation models•Dispersion models•Land-use regressionmodels•Hybrid models•Combine a model withtime-activity data, orpersonal/microenvironmental monitoring•Proximity models are leasteffective:•Can be confounded bySocioeconomic Status,Noise, other factors•Newer models of exposureare better•But should be validatedagainst some real-worlddata.Criteria for Inclusion of Toxicology andEpidemiology Studies•Quality of exposure assessment was key...•Studies had to include 1 or more of the followingexposure methods:•Distance from and/or length of roadways•Estimate of traffic density or intensity•Modeling of primary traffic-generated pollutant exposure•Studies of occupations characterized by exposure to traffic•Pollutant surrogates for traffic exposures (e.g., NO2, EC/BS,CO, benzene, etc.) onlyif data provided to validate thepollutant as a reasonably specific surrogate for such exposure2. What Can We Learn from Toxicology?(Example from a somewhat limited database):Effects of Traffic Exposure on Asthmatics (Zhang HEI 2009)Lung function decline in asthmatics comparing Hyde Park and Oxford Street, London(although symptoms did not increase...)3. What can we learn from epidemiology?Criteria for Causal InferenceFour categories to test whether traffic causes effects,based on:-how well studies controlled for confounding-consistency of the findings with other studies-quality of the method to estimate exposure•Sufficientevidence•Suggestivebut not sufficient•Inadequate and insufficientevidence•Suggestive ofno associationEpidemiologyHealth Outcomes Evaluated•Mortality (all cause, cardiopulmonary)•Cardiovascular morbidity•Respiratory disease•Asthma—childhood/adult•General respiratory symptoms•Lung function-childhood/adult/COPD•Health care utilization•Non-asthmatic allergy•Birth Outcomes•Cancer1.131.161.490.870.941.09 1.091.721.741.131.62.941.5800.511.522.533.544.55 per 10.3 ug/m3 in NO2 - 2nd year of life per 10.6 ug/m3 in NO2 - 4th year of life per 10.6 ug/m3 in NO2 - 4th year of life (Allergic Children) per 8.5 ug/m3 NO2 - 1st year of life per 8.5 ug/m3 NO2 - 2nd year of life per IQR NO2 - 1st year of life per IQR NO2 - 2nd year of life Gauderman 2005: Per 5.7 ppb NO2 Janssen 2003: per 18 ug/m3 NO2 Hirsch 1999: per 10ug/m3 NO2 Nordling 2008: per 44ug/m3 NOx Van Roosebroeck 2008: per 17ug/m3 Nicolai 2003: >=57.4 vs. < 57.4 ug/m3Brauer2002Brauer 2007 Gehring 2002 Morgenstern 2006 Other Authors

ODDS RATIO (95% CI)Exacerbation of Asthma SymptomsIncrease in Wheeze Per Increment NO2Synthesis ofEvidenceExacerbations withasthma—Sufficientfor causal associationReasonsLarge number ofstudies with adequatecontrol forconfounding andmostly precise effectestimatesTraffic Exposure and Doctor-Diagnosed AsthmaIncidence in ChildrenNO2Distance Density SpatialSynthesis of EvidenceSufficientORsuggestiveevidenceReasonsStudies that included bothtraffic-specific pollutantsand density measures mostconsistentLong-Term Traffic Exposure andCardiopulmonary Mortality1.221.381.841.701.05 1.051.041.071.451.391.131.950.911.11.21.31.41.51.61.71.81.922.1 Jerrett 2009: Circulatory Fickelstein 2005: Cardiovascular Fickelstein 2005: Stroke Gehring 2006: Cardiopulmonary Hoek 2002: Cardiopulmonary Maheswaran 2003: Stroke Beleen 2008c: Cardiovascular Beelen 2008c: Cardiovascular Beelen 2008c: Cardiovascular Jerrett 2009: Circulatory (All) Jerrett 2009: Circulatory (proximity to traffic) Jerrett 2005Residential distance from major road or highwayPer10ug/m3BSPer10ug/m3NO2Per 4 ppb NO2Per10ug/m3PM2.5

Relative Risks (95% CI)ProximityBS NO2PMSynthesis of EvidenceSuggestiveto infercausal association butnot yet sufficientReasonsToo few studiesRelative imprecision ofmost estimatesEffects of Traffic Exposure onBirth Outcomes•Synthesis ofEvidence•Insufficient evidence•Reasons•Only 4 studies metcriteria forinclusions0.50.7511.251.51.752 Quintile 2 vs. 1 Quintile 3 vs. 1 Quintile 4 vs. 1 Quintile 5 vs. 1 Quintile 2 vs. 1 Quintile 3 vs. 1 Quintile 4 vs. 1 Quintile 5 vs. 1 High SES Middle SES Low SES High SES Middle SES Low SES Quartile 2 vs. 1 Quartile 3 vs. 1 Quartile 4 vs. 1 NO2 per 10ug/m3 NO per 10ug/m3 PM2.5 per 1 ug/m3 <50m Highway <150m Highway <50m Major road NO2 per 10ug/m3 NO per 10ug/m3 PM2.5 per 1 ug/m3Pre-term birth &traffic density(Wilhelm 2003)Pre-term birth +LBW & trafficdensity (Wilhelm2003)Pre-term birthin summer &traffic density(Ponce 2005)Pre-term birthin winter &traffic density(Ponce 2005)Birthweight<3000g &PM2.5exposure(Slama 2007)Small for gestational age(Brauer 2008)LBW at > 37wks (Brauer2008)

RR (95% CI)Pre-Term PT/LBS SummerWinter LBWSGA LBWDensity DensityPT, Density PM2.5NOxPM2.5ProximityConclusionsExposure•Traffic-related pollutants impact ambient airquality on a broad spatial scale ranging fromroadside, to urban, to regional background•Based on synthesis of evidence, 300 to 500 metersfrom major road was identified as the near-sourcearea most impacted by traffic;•variations exist depending on meteorology, backgroundpollution, and local factorsIssues for Exposure Assessment•None of the pollutant surrogates considered met all criteria foran ideal surrogate•CO, benzene, and NOx [NO2] found in on-road vehicle emissions arealso major components of emissions from all sources•UF PM has not been used in epidemiologic studies so far. Itis difficult tomodel them because there are no emission inventories•Exposure models are important, but have various degrees ofutility to health studies•The proximity model is the most error-prone•Other models are better:•Dispersion models (need adequate data)•Land use regression models•Several approaches together (hybrid)Overall Conclusions•The data are incomplete on emissions, theirtransformations, and exposure assessment•There were, however, enough studies to find•Sufficientevidence for a causal association withexacerbation of asthma•Suggestiveevidence for a number of other healtheffects (mortality, lung function, respiratorysymptoms, and others)Overall Conclusions II•Limited evidence of effects butinadequate andinsufficientto infer causal associations:•Adult onset asthma•Health care utilization•COPD•Non-asthmatic allergy•Birth outcomes•CancersOverall Conclusions III•A caution: epidemiology studies are based on pastestimates of exposure•they may not provide an accurate guide to estimatinghealth associations in the future•However, given the large number of people livingwithin 300- 500 meters of a major road, the Panelconcluded that exposures to primary trafficgenerated pollutants are likely to be of public healthconcern and deserve attention.Thank You!Dan Greenbaumdgreenbaum@healtheffects.org