Abstract
BackgroundHazardous 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.MethodsTo 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.ResultsTotal 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.ConclusionsTraffic 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.
Highlights
Hazardous air pollutant exposures are common in urban areas contributing to increased risk of cancer and other adverse health outcomes
Measurements in all samples exceeded the limit of quantification (LOQ) for Sum of Benzene (BTEX) compounds and formaldehyde
Field blank concentrations were below the LOQ for all BTEX compounds and all but one formaldehyde sample
Summary
Hazardous air pollutant exposures are common in urban areas contributing to increased risk of cancer and other adverse health outcomes. The 1999 Amendments to the Clean Air Act identified 187 hazardous air pollutants (HAPs) subject to emissions based controls due to health effects associated with ambient exposures [1]. These regulations include controls on 174 stationary source categories to meet maximum achievable control technology standards and mobile source air toxics rules that reduce vehicle emissions through fuel controls, including lowering limits on benzene in gasoline beginning in 2011 [2]. HAPs commonly found in urban areas include formaldehyde and a group of aromatic volatile organic compounds (VOC): benzene, toluene, ethylbenzene, xylene (together known as BTEX). BTEX and formaldehyde play important roles in the photochemical reactions that form ozone [9]
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