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Racial Segregation Linked to Higher Cancer Risk
Report in Environmental Health Perspectives finds minorities living in highly segregated areas at 2.5 times the risk

[Research Triangle Park, NC] ] Minority populations living in highly segregated metropolitan areas in the U.S. are at more than 2.5 times the risk of cancer from air pollutants when compared to whites, according to a study accepted for publication today by the peer-reviewed journal Environmental Health Perspectives (EHP). The risk increased as the amount of segregation increased, and Hispanics in highly segregated areas were impacted most, with a risk 6.4 times that of whites. After controlling for neighborhood poverty indicators, and population density, the disparities in cancer risk persisted, though at a lower level.

For purposes of this study, the authors measured segregation as the proportion of people who would need to move in order to achieve an even racial/ethnic balance in every neighborhood of a city and its suburbs. Researchers analyzed over 45,000 census tracts in 309 metropolitan areas in the United States, analyzing the level of segregation in neighborhoods making up 79% of the U.S. population. Cancer risk estimates were derived for each neighborhood from 1996 air toxics data from the U.S. Environmental Protection Agency.

Although the study found a persistent racial and ethnic gap in cancer risk across all levels of poverty, there is no gradient that increases with rising poverty levels. This suggests that the influence of segregation on cancer risk is independent of the impact of poverty across racial categories.

Over 50% of the population included in this analysis live in highly segregated metro areas and 37% live in extremely segregated metro areas.

"We found a persistent relationship between increasing levels of racial/ethnic segregation and increased estimated cancer risk associated with ambient air toxics," according to the researchers.

Racial and ethnic groups were divided into six categories based on the census: Hispanics of any race, non-Hispanic Whites, non-Hispanic Blacks, non-Hispanic Asians and Pacific Islanders, non-Hispanic American Indians and Alaska Natives, and non-Hispanic persons of "other" races. The metropolitan areas were stratified into three segregation groups: low to moderately segregated, highly segregated, extremely segregated, as well as six regions: West, Border, Southern, Northeastern, Midwest, and Mountains and Plains.

"To our knowledge, our analysis is the first study to utilize a generalized multi-ethnic segregation measure for the evaluation of environmental health disparities," the researchers wrote.

The study assessed cancer risks using inhalation unit risk estimates, or the individual lifetime excess risk due to a chronic lifetime exposure to one unit of pollutant concentration, for each carcinogenic compound considered either carcinogenic to humans, likely to be carcinogenic to humans, or having suggestive evidence of carcinogenic potential. Among the sources of the air toxics studied, mobile sources such as on-road vehicles and airplanes, trains, and equipment made the most significant contribution to cancer risk, followed by area sources such as dry cleaners and auto body shops. The largest source of risk was diesel particulate emissions.

This study suggests that disparities associated with exposures to ambient air toxics are impacted by the degree of racial residential segregation. , These exposures may have environmental health significance for populations across racial and ethnic lines.

The authors of the study were Rachel Morello-Frosch and Bill M. Jesdale of Brown University. Funding for the research was provided in part by the Centers for Disease Control and Prevention and the Regents of the University of California for the Berkeley Center for Environmental Public Health Tracking. The views expressed are those solely of the authors and do not represent the views of the funding agency. The article is available free of charge at http://ehp.niehs.nih.gov/docs/2005/8500/abstract.html.

EHP is published by the National Institute of Environmental Health Sciences (NIEHS), part of the U.S. Department of Health and Human Services. EHP EHP is an Open Access journal. More information is available online at http://www.ehponline.org/. Brogan & Partners Convergence Marketing handles marketing and public relations for EHP, and is responsible for creation and distribution of this press release.

Editor's note: Working media can register to receive press releases via e-mail by visiting http://www.ehponline.org/press/, calling 919-653-2582, or e-mailing ehpmedia@brogan.com.