Although air quality has improved dramatically over the past 50 years, thanks in part to the Clean Air Act, people of color at every income level in the United States are still exposed to above-average levels of air pollution.
A team led by researchers from the University of Washington wanted to know whether the Clean Air Act can narrow these differences or whether a new approach is needed. The team compared two approaches that reflect key aspects of the Clean Air Act and a third approach not commonly used to see if it would be better to address inequalities in the contiguous US. The researchers used national emissions data to model each strategy: targeting specific emission sources in the US; require 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 inequalities, the community-specific approach eliminated pollution inequalities and reduced overall exposure to pollution.
The team published these findings on Oct. 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 differences, but we found that almost all sources lead to uneven exposure. So we thought, what is needed? Here we tried three approaches to see which are the best.” to address these inequalities,” said senior author Julian Marshall, a UW professor of civil and environmental engineering. “The two approaches reflecting aspects of the Clean Air Act have been quite weak in addressing inequalities. The third approach, targeting emissions in specific locations, is not done very often, but is something that overburdened communities have been asking for for years.”
Particulate matter pollution, or PM2.5, is less than 2.5 micrometers in diameter — about 3% of the diameter of a human hair. PM2.5 comes from vehicle exhaust gases; fertilizer and other agricultural emissions; electricity generation from fossil fuels; forest fires; and combustion of fuels such as wood, oil, diesel, petrol and coal. These tiny particles can lead to heart attacks, strokes, lung cancer and other diseases, and are estimated to be responsible for about 90,000 deaths per year in the U.S.
The researchers tested the three possible strategies using a tool called InMAP, which Marshall and other co-authors developed. InMAP models the chemistry and physics of PM2.5, including how it forms in the atmosphere, how it disappears, and how wind patterns move it from one location to another. The team modeled these approaches with national emissions data from 2014, as this was the most recent data set available at the time of this study.
The researchers looked at how efficiently and effectively each approach reduced the average exposure to pollution for all people and how well it eliminated the inequalities for people of color.
While the approaches to emission source and concentration standards were successful in reducing overall exposure across the country, these methods failed to address the differences in pollution.
“Our optimization models what happens when we maximize the reduction of inequalities. If an approach can’t address inequalities, even when it’s optimized to do so, then any real-world implementation of the approach won’t address inequalities either,” says lead author Yuzhou Wang, a doctoral student in civil and environmental engineering. “But we saw that even with less than 1% of emission reductions targeted at specific locations, the pollution differentials that have persisted for decades have been reduced to zero.”
Implementing this site-specific approach would require additional work to determine which locations are best to target and work with the communities there to determine how emissions can be reduced, the team said.
“Current regulations have improved average air pollution levels, but they have failed to address structural inequalities and have often failed to consider the voices and experiences of people in overburdened communities, including their requests to pay more attention to sources that affect their lives. communities,” Marshall said. “These findings reflect historical experiences. Because of redlining and other racist urban planning from many decades ago, many sources of pollution are more likely to be in black and brown communities. If we want to tackle current inequalities, we need an approach that reflects and recognizes this historical context.”
Other co-authors include Joshua Apte and Cesunica Ivey, both at the University of California, Berkeley; Jason Hill at the University of Minnesota; Regan Patterson at the University of California, Los Angeles; Allen Robinson at Carnegie Mellon University; and Christopher Tessum at the University of Illinois Urbana-Champaign. This research was funded by the US Environmental Protection Agency.