A Cancer Risk Assessment of Inner-City Teenagers Living in New York City and Los Angeles

Article excerpt

BACKGROUND: The Toxics Exposure Assessment Columbia-Harvard (TEACH) project assessed exposures and cancer risks from urban air pollutants in a population of high school teenagers in New York City (NYC) and Los Angeles (LA). Forty-six high school students participated in NYC and 41 in LA, most in two seasons in 1999 and 2000, respectively.

METHODS: Personal, indoor home, and outdoor home 48-hr samples of volatile organic compounds (VOCs), aldehydes, particulate matter with aerodynamic diameter [less than or equal to] 2.5 [micro]m, and particle-bound elements were collected. Individual cancer risks for 13 VOCs and 6 particle-bound elements were calculated from personal concentrations and published cancer unit risks.

RESULTS: The median cumulative risk from personal VOC exposures for this sample of NYC high school students was 666 per million and was greater than the risks from ambient exposures by a factor of about 5. In the LA sample, median cancer risks from VOC personal exposures were 486 per million, about a factor of 4 greater than ambient exposure risks. The VOCs with the highest cancer risk included 1,4-dichlorobenzene, formaldehyde, chloroform, acetaldehyde, and benzene. Of these, benzene had the greatest contributions from outdoor sources. All others had high contributions from indoor sources. The cumulative risks from personal exposures to the elements were an order of magnitude lower than cancer risks from VOC exposures.

CONCLUSIONS: Most VOCs had median upper-bound lifetime cancer risks that exceeded the U.S. Environmental Protection Agency (EPA) benchmark of 1 x [10.sup.-6] and were generally greater than U.S. EPA modeled estimates, more so for compounds with predominant indoor sources. Chromium, nickel, and arsenic had median personal cancer risks above the U.S. EPA benchmark with exposures largely from outdoors and other microenvironments. The U.S. EPA-modeled concentrations tended to overestimate personal cancer risks for beryllium and chromium but underestimate risks for nickel and arsenic.

KEY WORDS: aldehydes, cancer risk assessment, metals, personal exposures, VOCs. Environ Health Perspect 114:1558-1566 (2006). doi:10.1289/ehp.8507 available via http://dx.doi.org/ [Online 15 June 2006]

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The health risks associated with exposures to common urban air pollutants have focused primarily on the six U.S. Environmental Protection Agency (EPA) criteria air pollutants. Much less is known about exposures and adverse health impacts of the mix of > 100 hazardous air pollutants (HAPs) identified by the U.S. EPA in the 1990 Clean Air Act Amendments as posing health risks to the general population. One important chronic health impact associated with exposures to HAPs is cancer. Of the 188 HAPs, 91 compounds are known, probable, or suspected carcinogens with available inhalation unit risks, including many volatile organic compounds (VOCs) (Woodruff et al. 2000).

Most individuals are exposed to HAPs while indoors (residence, workplace, school, and vehicles), where people spend most of their time. Indoor concentrations of HAPs, however, can originate from outdoor as well as indoor sources. Regulatory efforts by the U.S. EPA have focused primarily on ambient concentrations (emissions, measurement, and modeling). For example, in 1995 the U.S. EPA undertook the Cumulative Exposure Project (CEP), modeling concentrations of 148 HAPs using emissions data in conjunction with an air dispersion model, the Assessment System for Population Exposure Nationwide (Woodruff et al. 1998). The results from the CEP modeling efforts showed that in both New York City (NYC) and Los Angeles (LA), cancer risks of most VOCs exceeded the U.S. EPA benchmark (1 x [10.sup.-6] risk for a lifetime) by at least a factor of 2 but as much as a factor of 100 for some compounds (Caldwell et al. 1998). More recently, the U.S. EPA conducted the National Air Toxics Assessment (NATA) using emissions data from 1996 for 33 priority HAPs, most of them VOCs (U. …