Environmental Inequality in Exposures to Airborne Particulate Matter Components in the United States
Published on Environmental Health Perspectives
Background: Growing evidence indicates that toxicity of fine particles (PM2.5) differs by chemical component. Exposure to components may differ by population.
Objectives: We investigated whether exposures to PM2.5 components differ by race/ethnicity, age, and socio-economic status (SES).
Methods: Long-term exposures (2000-2006) were estimated for 215 US census tracts for PM2.5 and 14 PM2.5 components. Population-weighted exposures were combined to generate overall estimated exposures by race/ethnicity, education, poverty status, employment, age, and earnings. Population characteristics for tracts with and without PM2.5 component monitors were compared.
Results: Larger disparities in estimated exposures were observed for components than for PM2.5 total mass. For race/ethnicity, whites generally had the lowest exposures. Non-Hispanic blacks had higher exposures than whites for 13 of the 14 components. Hispanics generally had the highest exposures (e.g., 152% higher than whites for chlorine, 94% higher for aluminum). Young persons (0-19yrs) had levels as high as or higher than other ages for all exposures except sulfate. Persons with lower SES had higher estimated exposures, with some exceptions. For example, a 10% increase in the proportion unemployed was associated with a 20.0% increase in vanadium and an 18.3% increase in elemental carbon. Census tracts with monitors had more non-Hispanic blacks, lower education and earnings, and higher unemployment and poverty than tracts without monitors.
Conclusions: Exposures to PM2.5 components differed by race/ethnicity, age, and SES. If some components are more toxic than others, certain populations are likely to suffer higher health burdens. Demographics differed between populations covered and not covered by monitors.