A new approach, not currently outlined by the Clean Air Act, could eliminate disparities in air pollution

While air quality has improved dramatically over the past 50 years thanks in part to the Clean Air Act, people of color at all income levels in the United States are still exposed to levels of pollution looks above average.

A team led by researchers from the University of Washington wanted to know if the Clean Air Act is able to reduce these disparities or if a new approach would be needed. The team compared two approaches that reflect key aspects of the Clean Air Act and a third approach that is not commonly used to see if it would be more effective in addressing disparities between the contiguous United States. The researchers used national emissions data to model each strategy: target emissions sources across the United States; requiring regions to adhere to specific concentration standards; or reducing emissions in specific communities.

While the first two approaches—based on the Clean Air Act—did not eliminate disparities, the community-specific approach eliminated pollution disparities and reduced overall pollution exposure.

The team published these results on October 24 in the Proceedings of the National Academy of Sciences.

“In previous research, we wanted to know which sources of pollution were responsible for these disparities, but we found that almost all sources lead to unequal exposures. So we thought, what was it going to take? Here, we tried three approaches to see which one is best for addressing these disparities,” said lead author Julian Marshall, a UW professor of civil and environmental engineering. “The two approaches that reflect aspects of the Clean Air Act were quite weak to deal with disparities. The third approach, targeting broadcasts in specific locations, isn’t commonly used, but it’s something that overburdened communities have been asking for for years.”

Fine particle pollution, or PM2.5, measures less than 2.5 micrometers in diameter, or about 3% of the diameter of a human hair. PM2.5 comes from vehicle exhaust; fertilizers and other agricultural emissions; generation of electricity from fossil fuels; Forest fires; and the combustion of fuels such as wood, oil, diesel, gasoline and coal. These tiny particles can lead to heart attacks, strokes, lung cancer and other illnesses, and are estimated to be responsible for around 90,000 deaths each year in the United States.

The researchers tested the three potential strategies using a tool called InMAP, developed by Marshall and other co-authors. InMAP models the chemistry and physics of PM2.5, including how it forms in the atmosphere, how it dissipates, and how winds move it from place to place. The team modeled these approaches with national emissions data from 2014, as this was the most recent dataset available at the time of this study.

The researchers looked at how effectively each approach reduced average pollution exposure for all people and how well it eliminated disparities for people of color.

Although the emission source and concentration standards approaches have been successful in reducing overall exposure across the country, these methods have failed to address pollution disparities.

“Our optimization models what happens if we maximize disparity reductions. If an approach cannot handle disparities even when it is optimized to do so, then any real implementation of the approach will not handle either disparities,” said lead author Yuzhou Wang, a civil and environmental engineering doctoral student. “But we’ve seen that even with less than 1% of emissions reductions targeting specific locations, pollution disparities that have persisted for decades have been reduced to zero.”

Implementing this location-specific approach would require additional work to identify which locations would be best to target and work with the communities there to identify how to reduce emissions, the team said.

“Current regulations have improved average levels of air pollution, but they have failed to address structural inequalities and have often ignored the voices and lived experiences of people in overburdened communities, including their demands to grant greater attention to sources impacting their communities,” Marshall said. “These findings reflect historical experiences. Due to redlining and other racist urban planning decades ago, many sources of pollution are more likely to be located in black and brown communities. If we wish address current inequalities, we need an approach that reflects and recognizes this historical context.”

Additional co-authors are Joshua Apte and Cesunica Ivey, both of the University of California, Berkeley; Jason Hill at the University of Minnesota; Regan Patterson of the University of California, Los Angeles; Allen Robinson of Carnegie Mellon University; and Christopher Tessum of the University of Illinois at Urbana-Champaign. This research was funded by the United States Environmental Protection Agency.

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Materials provided by University of Washington. Original written by Sarah McQuate. Note: Content may be edited for style and length.