Environmental Inequality in Exposures to Airborne Particulate Matter Components in the United States

Michelle L. Bell and Keita Ebisu

School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, USA

Abstract

Background: Growing evidence indicates that toxicity of fine particulate matter ≤ 2.5 μm in diameter (PM_2.5) differs by chemical component. Exposure to components may differ by population.

Objectives: We investigated whether exposures to PM_2.5 components differ by race/ethnicity, age, and socioeconomic status (SES).

Methods: Long-term exposures (2000 through 2006) were estimated for 215 U.S. census tracts for PM_2.5 and for 14 PM_2.5 components. Population-weighted exposures were combined to generate overall estimated exposures by race/ethnicity, education, poverty status, employment, age, and earnings. We compared population characteristics for tracts with and without PM_2.5 component monitors.

Results: Larger disparities in estimated exposures were observed for components than for PM_2.5 total mass. For race/ethnicity, whites generally had the lowest exposures. Non-Hispanic blacks had higher exposures than did 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 (0–19 years of age) 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 did tracts without monitors.

Conclusions: Exposures to PM_2.5 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.

Key words: air pollution, chemical components, environmental justice, particulate matter, PM_2.5, race, socioeconomic status. 

Environ Health Perspect 120:1699–1704 (2012). http://dx.doi.org/10.1289/ehp.1205201 [Online 10 August 2012]

Address correspondence to M.L. Bell, School of Forestry and Environmental Studies, Yale University, 195 Prospect St., New Haven, CT 06511 USA. Telephone: (203) 432-9869. Fax: (203) 436-9135. E-mail: michelle.bell@yale.edu

Supplemental Material is available online (http://dx.doi.org/10.1289/ehp.1205201).

This work was funded by the U.S. Environmental Protection Agency through the Harvard University Clean Air Center (EPA RD-83479801) and by the National Institutes of Health (grants R01-ES019560 and R01-ES019587).

The authors declare they have no actual or potential competing financial interests.

Received 12 March 2012; Accepted 10 August 2012; Online 10 August 2012.