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Air Pollution Inequality Growing in Massachusetts

SPH study finds exposure falls along racial, ethnic, income, and education lines


Before Flint, Michigan sparked a national conversation about inequality and contaminated water, mounting evidence was already showing that lower-income and minority communities were more likely to be exposed to air pollution. A new study by School of Public Health researchers has found persistent and even growing inequality in how much ambient air pollution different Massachusetts communities are exposed to along racial/ethnic, income, and education lines, despite the state’s major reductions in air pollution overall.

The study, supported by the National Institutes on Minority Health and Health Disparities and by the United States Environmental Protection Agency, was published online in Environmental Research.

While numerous previous studies have shown disparities in air pollution exposure at one point in time, the current study was one of the first to track those disparities over space and time, allowing for a more nuanced picture of exposures as demographics shift in a given area.

It found that concentrations of nitrogen dioxide (NO2) and fine particulate matter (PM2.5) decreased across the state between 2003 and 2010, but exposure remained higher in urban, predominantly Hispanic, non-Hispanic Asian, and non-Hispanic black communities. Exposure inequality among communities with different average incomes and education levels also persisted, but was less dramatic than racial/ethnic disparities. Within the state’s cities, the researchers found exposure inequality actually increased slightly between racial/ethnic groups during the study period.

“Although ambient air pollution concentrations have decreased across all of Massachusetts, these reductions had a higher relative impact on populations that were already in the lowest exposure categories, hence the increase in exposure inequality,” says Patricia Fabian, School of Public Health research assistant professor of environmental health and the study’s senior author.

NO2 and PM2.5 are associated with a range of health effects, including higher risk of asthma and respiratory infections, cardiovascular disease, premature birth and low birth weight, and increased risk of autism spectrum disorders. The authors noted that exposure to NO2 was more dramatically unequal than exposure to PM2.5, perhaps because NO2 is strongly linked to automobile exhaust, which can vary within a city based on traffic patterns, while PM2.5 is derived from a wide variety of sources and tends to have more regional concentrations.

Using data from the 2000 and 2010 Census and the 2006–2010 American Community Survey on race/ethnicity, income, educational attainment, and rural/urban land classification, the researchers calculated exposures using modeled PM2.5 concentrations from 2003 to 2010 and NO2 concentrations from 2005 to 2010. The researchers then characterized the disparities using the Atkinson Index, a quantitative measure for relative inequality.

The researchers found the average annual PM2.5 concentrations across the state decreased by 35 percent between 2003 and 2010, and the average annual NO2 concentrations decreased by 24 percent between 2005 and 2010. However, the Hispanic and non-Hispanic black populations continued to have the highest PM2.5 exposures, and Hispanic and non-Hispanic Asian populations had the highest NO2 exposures. The gap between PM2.5 exposures for non-Hispanic black populations and non-Hispanic white populations remained the same, while the gap between Hispanic and non-Hispanic white populations slightly increased.

“Greater inequalities in urban areas, where there is often substantial segregation, reinforces the importance of targeted exposure reduction strategies within vulnerable populations and neighborhoods,” the authors wrote. By looking at these inequalities over time, the authors said, the study points to the possibility that sociodemographic changes may impact land-use decisions, environmental policy enforcement, and other factors influencing emissions.

More longitudinal, individual-level studies are needed to understand this “complex dynamic,” the authors wrote.

The study came out of the Center for Research on Social Stressors in Housing Across the Life Course (CRESSH), a partnership between SPH, the Harvard T.H. Chan School of Public Health, Health Resources in Action, and GreenRoots. CRESSH studies environmental health disparities in low-income communities and throughout Massachusetts.

The authors noted that outdoor ambient air pollution exposures in this study do not tell the whole story: “low socioeconomic status groups may be disproportionately exposed to indoor-generated exposures or from indoor exposure to outdoor pollutants due to older, leakier housing stock,” they wrote. “Taking into account the full exposure profile of both indoor and outdoor-generated air pollutants may reveal a more striking characterization of exposure inequality between population groups.”

Other authors on the study included Anna Rosofsky (SPH’18); Jonathan Levy, SPH professor of environmental health; Patricia Janulewicz (SPH’06,’08), SPH assistant professor of community health sciences; and Antonella Zanobetti, principal research scientist in the Department of Public Health at Harvard T.H. Chan School of Public Health.

Michelle Samuels can be reached at msamu@bu.edu.


3 Comments on Air Pollution Inequality Growing in Massachusetts

  • Kitty on 01.12.2018 at 4:41 pm

    I am disappointed that the article doesn’t suggest WHY ambient air pollutants might be higher for areas where certain populations live.

    I have never heard of “non-Hispanic” Asians. What are they?

    • Anno on 01.16.2018 at 4:31 pm

      Just want to reply to the comment of “non-Hispanic” Asians-
      People define their racial/ethnicity differently. It can totally be true that an Asian person considers themselves having Hispanic lineages. Acknowledging subtle differences in self-identity to me is important.
      -Also “sociodemographic changes may impact land-use decisions, environmental policy enforcement, and other factors influencing emissions”

  • World Commenter on 01.12.2018 at 7:57 pm

    Need to change zoning rules so every locality gets highways, factories, commercial and industrial establishments and has exactly the same environmental impacts, Beacon Hill and Brookline to Everett and Quincy Neck.

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