Race/Ethnicity,Residential Segregation,and Exposure to Ambient Air Pollution: The Multi-Ethnic Study of Atherosclerosis (MESA)

Objectives. We described the associations of ambient air pollution exposure with race/ethnicity and racial residential segregation.Methods. We studied 5921 White, Black, Hispanic, and Chinese adults across 6 US cities between 2000 and 2002. Household-level fine particulate matter (PM_2.5) and nitrogen oxides (NO_X) were estimated for 2000. Neighborhood racial composition and residential segregation were estimated using US census tract data for 2000.Results. Participants in neighborhoods with more than 60% Hispanic populations were exposed to 8% higher PM_2.5 and 31% higher NO_X concentrations compared with those in neighborhoods with less than 25% Hispanic populations. Participants in neighborhoods with more than 60% White populations were exposed to 5% lower PM_2.5 and 18% lower NO_X concentrations compared with those in neighborhoods with less than 25% of the population identifying as White. Neighborhoods with Whites underrepresented or with Hispanics overrepresented were exposed to higher PM_2.5 and NO_X concentrations. No differences were observed for other racial/ethnic groups.Conclusions. Living in majority White neighborhoods was associated with lower air pollution exposures, and living in majority Hispanic neighborhoods was associated with higher air pollution exposures. This new information highlighted the importance of measuring neighborhood-level segregation in the environmental justice literature.In the United States, race/ethnicity is highly correlated with residential location, with Whites and minorities often living segregated from one another.1,2 Differential residential location can result in important racial/ethnic differences in environmental exposures, such as air pollution.1,3–6 Epidemiological studies have consistently shown increased risk for morbidity and mortality from cardiovascular7–10 and respiratory diseases (chronic obstructive pulmonary disease, asthma, and lung cancer)8,11–14 associated with exposure to ambient air pollution, including exposure to fine particulate matter (particles < 2.5 μm in aerodynamic diameter PM_2.5]) and nitrogen oxides (NO_X; sum of nitric oxide, nitrogen dioxide, nitrous acid, and nitric acid).15–21 Predominantly minority areas are more likely to have22,23 or be more proximal4,24,25 to hazardous sites or air pollution sources, including point sources and roadway traffic. However, few studies have investigated how individual- or household-level exposure estimates are associated with race/ethnicity.In addition to proximity to pollution sources, poor enforcement of environmental regulations in minority communities and inadequate response to community complaints may also contribute to higher exposure to environmental hazards in minority communities.1 These institutional factors reflect physical, political, social, and economic characteristics of neighborhoods that are often correlated with their racial/ethnic composition and the level of racial residential segregation. For these reasons, measures of neighborhood racial/ethnic composition and racial residential segregation may be associated with environmental exposures independently of the individual race/ethnicity of residents. Despite the importance of contextual information for advancing research for environmental justice, few studies have simultaneously examined how neighborhood characteristics and the race/ethnicity of study participants are related to environmental exposures or examined racial residential segregation as it relates to air pollution exposure.6,26Also, most studies have compared exposure among Whites and Blacks with few studies including other races/ethnicities.4,24,27–29 Our objective in this study was to describe associations of exposure to ambient air pollution, estimated by annual average PM_2.5 and NO_X concentrations at the household level, with race/ethnicity, neighborhood racial/ethnic composition, and racial/ethnic residential segregation in White, Black, Hispanic and Chinese adults who participated in the Multi-Ethnic Study of Atherosclerosis (MESA) in 6 US communities.