Spatial variability in levels of benzene, formaldehyde, and total benzene, toluene, ethylbenzene and xylenes in New York City: a land-use regression study

Kheirbek Iyad, Johnson Sarah, Ross Zev, Pezeshki Grant, Ito Kazuhiko, Eisl Holger, Matte, Matte Thomas

Description

Hazardous air pollutant exposures are common in urban areas contributing to increased risk of cancer and other adverse health outcomes. While recent analyses indicate that New York City residents experience significantly higher cancer risks attributable to hazardous air pollutant exposures than the United States as a whole, limited data exist to assess intra-urban variability in air toxics exposures. Methods To assess intra-urban spatial variability in exposures to common hazardous air pollutants, street-level air sampling for volatile organic compounds and aldehydes was conducted at 70 sites throughout New York City during the spring of 2011. Land-use regression models were developed using a subset of 59 sites and validated against the remaining 11 sites to describe the relationship between concentrations of benzene, total BTEX (benzene, toluene, ethylbenzene, xylenes) and formaldehyde to indicators of local sources, adjusting for temporal variation. Results Total BTEX levels exhibited the most spatial variability, followed by benzene and formaldehyde (coefficient of variation of temporally adjusted measurements of 0.57, 0.35, 0.22, respectively). Total roadway length within 100 m, traffic signal density within 400 m of monitoring sites, and an indicator of temporal variation explained 65% of the total variability in benzene while 70% of the total variability in BTEX was accounted for by traffic signal density within 450 m, density of permitted solvent-use industries within 500 m, and an indicator of temporal variation. Measures of temporal variation, traffic signal density within 400 m, road length within 100 m, and interior building area within 100 m (indicator of heating fuel combustion) predicted 83% of the total variability of formaldehyde. The models built with the modeling subset were found to predict concentrations well, predicting 62% to 68% of monitored values at validation sites. Conclusions Traffic and point source emissions cause substantial variation in street-level exposures to common toxic volatile organic compounds in New York City. Land-use regression models were successfully developed for benzene, formaldehyde, and total BTEX using spatial indicators of on-road vehicle emissions and emissions from stationary sources. These estimates will improve the understanding of health effects of individual pollutants in complex urban pollutant mixtures and inform local air quality improvement efforts that reduce disparities in exposure.

Sujets

• Benzène
• Formaldehyde
• BTEX
• Air pollution
• Traffic

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 9
• Langue: English

Extrait

Kheirbek
etal.EnvironmentalHealth
2012,
11
:51
http://www.ehjournal.net/content/11/1/51

RESEARCH

OpenAccess

Spatialvariabilityinlevelsofbenzene,
formaldehyde,andtotalbenzene,toluene,
ethylbenzeneandxylenesinNewYorkCity:
aland-useregressionstudy
IyadKheirbek
1*
,SarahJohnson
1
,ZevRoss
2
,GrantPezeshki
1
,KazuhikoIto
1
,HolgerEisl
3
andThomasMatte
1

Abstract
Background:
Hazardousairpollutantexposuresarecommoninurbanareascontributingtoincreasedriskof
cancerandotheradversehealthoutcomes.WhilerecentanalysesindicatethatNewYorkCityresidentsexperience
significantlyhighercancerrisksattributabletohazardousairpollutantexposuresthantheUnitedStatesasawhole,
limiteddataexisttoassessintra-urbanvariabilityinairtoxicsexposures.
Methods:
Toassessintra-urbanspatialvariabilityinexposurestocommonhazardousairpollutants,street-level
airsamplingforvolatileorganiccompoundsandaldehydeswasconductedat70sitesthroughoutNewYorkCity
duringthespringof2011.Land-useregressionmodelsweredevelopedusingasubsetof59sitesandvalidated
againsttheremaining11sitestodescribetherelationshipbetweenconcentrationsofbenzene,totalBTEX
(benzene,toluene,ethylbenzene,xylenes)andformaldehydetoindicatorsoflocalsources,adjustingfor
temporalvariation.
Results:
TotalBTEXlevelsexhibitedthemostspatialvariability,followedbybenzeneandformaldehyde(coefficient
ofvariationoftemporallyadjustedmeasurementsof0.57,0.35,0.22,respectively).Totalroadwaylengthwithin
100m,trafficsignaldensitywithin400mofmonitoringsites,andanindicatoroftemporalvariationexplained
65%ofthetotalvariabilityinbenzenewhile70%ofthetotalvariabilityinBTEXwasaccountedforbytrafficsignal
densitywithin450m,densityofpermittedsolvent-useindustrieswithin500m,andanindicatoroftemporal
variation.Measuresoftemporalvariation,trafficsignaldensitywithin400m,roadlengthwithin100m,and
interiorbuildingareawithin100m(indicatorofheatingfuelcombustion)predicted83%ofthetotalvariability
offormaldehyde.Themodelsbuiltwiththemodelingsubsetwerefoundtopredictconcentrationswell,
predicting62%to68%ofmonitoredvaluesatvalidationsites.
Conclusions:
Trafficandpointsourceemissionscausesubstantialvariationinstreet-levelexposurestocommon
toxicvolatileorganiccompoundsinNewYorkCity.Land-useregressionmodelsweresuccessfullydeveloped
forbenzene,formaldehyde,andtotalBTEXusingspatialindicatorsofon-roadvehicleemissionsandemissions
fromstationarysources.Theseestimateswillimprovetheunderstandingofhealtheffectsofindividualpollutants
incomplexurbanpollutantmixturesandinformlocalairqualityimprovementeffortsthatreducedisparities
inexposure.
Keywords:
Benzene,Formaldehyde,BTEX,Landuseregression(LUR),Airtoxics,Traffic,Hazardousair
pollutants(HAP)

*Correspondence:[e-mail]
1
NewYorkCityDepartmentofHealthandMentalHygiene,Bureauof
EnvironmentalSurveillanceandPolicy,125WorthStreet,CN34E,NewYork,
NY10013,USA
Fulllistofauthorinformationisavailableattheendofthearticle
©2012Kheirbeketal.;licenseeBioMedCentralLtd.ThisisanOpenAccessarticledistributedunderthetermsoftheCreative
CommonsAttributionLicense(http://creativecommons.org/licenses/by/2.0),whichpermitsunrestricteduse,distribution,and
reproductioninanymedium,providedtheoriginalworkisproperlycited.

Kheirbek
etal.EnvironmentalHealth
2012,
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Background
Despiteregulatorycontrols,urbanpopulationsareexposed
totoxicairpollutantswithpotentialtocausecanceror
otherserioushealtheffects.The1999Amendmentstothe
CleanAirActidentified187hazardousairpollutants
(HAPs)subjecttoemissionsbasedcontrolsduetohealth
effectsassociatedwithambientexposures[1].Theseregu-
lationsincludecontrolson174stationarysourcecategories
tomeetmaximumachievablecontroltechnologystandards
andmobilesourceairtoxicsrulesthatreducevehicleemis-
sionsthroughfuelcontrols,includingloweringlimitson
benzeneingasolinebeginningin2011[2].
HAPscommonlyfoundinurbanareasincludeformal-
dehydeandagroupofaromaticvolatileorganiccom-
pounds(VOC):benzene,toluene,ethylbenzene,xylene
(togetherknownasBTEX).Amongthese,benzeneand
formaldehydeareclassifiedbytheInternationalAgency
forResearchonCancerashumancarcinogens(Group
1);botharekeydriversofestimatedcancerriskfromor-
ganicHAPsintheUS[3,4].OtherBTEXcompounds--
toluene,ethylbenzene,andxylene--havebeenfoundto
produceadversehealtheffectsincludingrespiratoryand
neurologicaleffects[5-7]andreacttoformsecondary
organicaerosols,contributingtoambientfineparticulate
matter(PM
2.5
)[8].BTEXandformaldehydealsoplay
importantrolesinthephotochemicalreactionsthat
formozone[9].
Recentanalysessuggestthat49%ofNewYorkCity
residentsliveincensustractsexceedingthe1in10,000
HAP-attributablecancerriskbenchmarkcomparedto
4.8%ofthepopulationnationwide,withthemajority
oftheriskattributedtobenzeneandformaldehyde
exposures[10,11].PrimarylocalsourcesofBTEXare
on-roadandnon-roadgasolinevehiclesandengines,
withemissionsfrompetroleumtransport/storageand
solventusagealsomakingsubstantialcontributions[12].
On-andnon-roadgasolineanddieselvehiclesand
enginesarealsopredominantsourcesofprimaryformal-
dehydeemissionsinNYCwithadditionalcontributions
fromstationary-sourcefuelcombustion[12].Formalde-
hydeisalsoformedsecondarilybyphotooxidationof
hydrocarbons.AmbientformaldehydelevelsinNew
YorkCityhavebeenobservedtopeakinsummer
months,likelyduetoseasonalincreasesinphotochem-
icalactivity[13].
Whilenationalairtoxicsregulationshavereduced
exposures,thelimitednumberofmonitoringsitesin
urbanareasrestrictstheabilitytoassessspatialvariation
inconcentrationswithincitiesfordevelopinglocalcon-
trolpolicies.Forexample,inNewYorkCitythereare
currentlysixregulatorymonitorsreportingVOCmea-
surementsandfivereportingaldehydes,withmonitors
operatingonlyeverysixthday[14].Whilethisnetwork
providesvaluableinformationonairtoxictrendsuseful

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inevaluatingexposureandregulatingozone,theyare
notsufficienttounderstandfinescaleintra-urbanspatial
variationinconcentrationsduetolocalizedsourcessuch
astraffic[15,16].
Recently,land-useregression(LUR)modelshavebeen
increasinglyusedtoestimateintra-urbanspatialvari-
abilityofairpollutantsandindevelopingexposureesti-
matesforepidemiologicalresearch[17,18].Theyhave
beenusedinNewYorkCitytodevelopexposureesti-
matesforfineparticulatematter(PM
2.5
),oxidesofnitro-
gen(NO
x
),andsulfurdioxide(SO
2
)(Cloughertyetal.
submitted2011,[19]).WhilemanyLURstudiesfocuson
nitrogendioxideNO
2
andPM
2.5
,theyhavealsobeen
usedtoestimateBTEXconcentrations[16,20-23].
Thispaperevaluatesspatialvariationinbenzene,
totalBTEXandformaldehydeconcentrationsacross
NewYorkCityusingasaturationsamplingcampaign
conductedinthespringof2011andland-useregres-
sionmodeling.
Methods
Spatialandtemporalallocationofsites
BTEXandformaldehydemonitoringwasconductedata
subsetofthe150sitesroutinelymonitoredforPM
2.5
,
elementalcarbon,PM
2.5
constituents,NO
x
,SO
2
and
ozonethroughoutNYCaspartoftheNewYorkCity
CommunityAirSurvey(NYCCAS)network,aninitiative
withintheCity
’
ssustainabilityplan,PlaNYC[24].The
NYCCASmonitoringnetworksiteswereselectedtocap-
turetherangeinvariationofkeylocalemissionssources
whileprovidingadequatespatialcoveragethroughout
theCity.Adescriptionoftheselectionprocessforthese
150sitesisdescribedelsewhere(Matteetal.submitted
2011).Inshort,120siteswereselectedformonitoring
throughstratifiedrandomsamplingof7,756300mx
300mgridcellswithoversamplinginareasofhightraf-
ficandhighbuildingdensity-indicatorsoftwocategor-
iesofimportantlocalemissionssources-toaccountfor
skeweddistributionsofthesesourceproxieswithinNew
YorkCity.Wechosebuildingdensityratherthanpopu-
lationdensityasanindicatorofsourceactivitysuitable
forbothresidentialandcommercialareasofthecity.
Thirtyadditionalsiteswereselectedtofillspatialgaps
andcaptureareasofinterest.
Oftheoriginal150sites,weselected70sitesforair
toxicsmonitoring(referredtoas
“
distributed
”
sites)by
firstretaining21sitesthatweregeographicallyisolated
fromothermonitoringlocationsorhadproducedhigh
residualsinourpriorstatisticalmodelsforNO
x
,SO
2
,
PM
2.5
,andEC.Thesesiteswereincludedtoensure
thatthemonitoringcapturedafullrangeoftrafficand
land-usesettings.Wethenrandomlyselectedfromthe
remainingavailablesites.Wecomparedthedistribu-
tionsofthese70sitesinrelationtotrafficandbuilding

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densitytothedistributionintheoriginal150sitesto
confirmthatsimilarcoverageofmajorsourcedensity
wasachievedinthesubsetofsitesselectedforairtoxics
monitoring(Table1).Threereferencesiteswereselected
inparks,awayfrommajorsources,inCentralParkin
Manhattan,QueensCollegeinQueens,andLaTourette
GolfCourseinStatenIsland(Figure1).
WecollectedsamplesofBTEXandformaldehydeat
eachofthe70distributedsites,14ofwhichwereallo-
catedatrandomtoeachoffivetwo-weeksessions,from
3/22/2011to6/1/2011.Atthethreereferencesites,sam-
pleswerecollectedduringallfivesessionstoassesscity-
widetemporalva