Oil spills and trash are obvious forms of pollution. Others, though, are far more silent but can be just as deadly. Air pollution, for example, kills somewhere between 100,000 to 200,000 Americans each year. A study published Wednesday in the journal Nature examines the trends in air pollution exposure over time, looking specifically at its disparate impacts on Black, Asian, Latino, Native, and white Americans. The findings confirm some troubling truths about the links between air pollution exposure and systemic racism.
One type of air pollution, PM2.5, is arguably the greatest environmental risk factor for human mortality. PM2.5 is fine particulate matter that’s roughly 2.5 microns or less in size — much smaller than even a human hair. When enough accumulates in the air around us, it can create smog that clogs up the skies in urban areas.
The study confirms the devastating effects of PM2.5 air pollution aren’t felt equally. Some racial and ethnic groups in America bear the effects of this air pollution at higher rates than others.
The discovery — The researchers reveal that overall, PM2.5 air pollution levels declined between 2000 and 2016. However, this trend masked persisting and troubling racial disparities in air pollution exposure across the same period.
“The reduction in PM2.5 levels over the years in the United States has been consistently accompanied with persisting disparities among both racial/ethnic and income groups,” Abdulrahman Jbaily, a co-author on the study and a postdoctoral fellow at the Harvard T.H. Chan School of Public Health, tells Inverse.
The scientists identified six links between race, income, and PM2.5. air pollution exposure between 2000 and 2016:
- Areas with higher-than-average Black, Asian, Hispanic, or Latino populations were consistently exposed to greater levels of PM2.5 air pollution than neighborhoods with predominantly white or Native American residents.
- There was a steeper decline in PM2.5 levels in areas with 70 percent or more white residents compared to areas with greater numbers of Black residents.
- Lower-income areas were exposed to slightly higher average PM2.5 air pollution levels than higher-income areas.
- In a given zip code, as the Black population increased, PM2.5 concentrations consistently rose, with a sharp increase in neighborhoods with greater than 85 percent Black residents. Areas with a higher percentage of Hispanic and Latino residents experienced similar trends. There wasn’t enough data on neighborhoods with greater than 60 percent Asian Americans to draw more detailed conclusions.
- Native Americans consistently experienced the lowest levels of PM2.5 exposure.
- Black, Asian, Hispanic, and Latino Americans were also exposed to levels of PM2.5 air pollution higher than 8 μg m−3 (a measure of how concentrated a pollutant is in the air per cubic meter). This is the standard researchers estimate will be the likely limit for air pollution going forward. Overall, the percentage of Americans exposed to this level of air pollution dropped from 89 percent in 2000 to 41 percent in 2016.
The data “shows that PM2.5 reductions between 2000 and 2016 have not benefited all areas of the US equally,” the researchers conclude in the study.
What’s even more troubling: Some racial and ethnic groups were exposed to PM2.5 levels “even above safety standards set by the EPA and the WHO,” Jbaily says, highlighting how these communities are not protected by current environmental regulations.
Why it matters — Although recent reports show air pollution is on the decline in the U.S., these reports do not take into account the disparate impacts on racial and ethnic groups.
These findings are crucial because they provide concrete data to support what many researchers have long suspected: Harmful impacts of air pollution are disproportionately borne by racial and ethnic minorities.
For example, according to the U.S. Department of Health and Human Services, in 2018, Black Americans were 40 percent more likely to experience asthma than non-Hispanic, white Americans, and three times more likely to die from asthma. Numerous studies have documented links between air pollution and childhood asthma.
To address these disparities, the scientists behind the new study recommend “targeted air pollution reduction strategies… may be needed to cause a decrease in relative disparities” in PM2.5 exposure to Black, Latino, and Asian Americans.
“While policymaking is outside the scope of our work, we believe that in general, policies that take into account targeting environmental disparities — in addition to pollution reduction — are indeed favorable,” Jbaily says.
Further, the researchers suggest that the air pollution exposure limits set by the U.S. Environmental Protection Agency and the World Health Organization might not be strict enough. Currently, the WHO sets PM2.5 air pollution exposure limits to 10 μg m−3, and the EPA sets its National Ambient Air Quality Standards to 12 μg m−3.
How they made the discovery — Researchers developed a data platform that connects demographic information from the U.S. Census Bureau with data on average PM2.5 air pollution concentrations.
The scientists analyzed this data across 32,000 zip codes, tracking the levels of PM2.5 air pollution by race and income between 2000 and 2016.
What’s next — There are some important caveats that limit the scope of the study. The scientists looked at average PM2.5 concentrations across broad zip codes, but they note that a more precise analysis of PM2.5 air pollution based on smaller Census blocks might yield stronger associations between PM2.5 air pollution exposure and race.
The study also doesn’t identify any causal mechanisms that would explain the differences in air pollution exposure between racial and ethnic groups. Yet the findings were consistent across urban and rural areas, suggesting the issue is more complex than simple associations between greater air pollution and higher concentrations of people of color in cities.
The scientists seek to examine these disparities in greater detail in future studies.
But, as the authors point out, their current research could have an immediate impact, by providing better, more targeted information on where air pollution is occurring in the United States and who is most affected by it.
Abstract: Air pollution contributes to the global burden of disease, with ambient exposure to fine particulate matter of diameters smaller than 2.5 μm (PM2.5) being identified as the fifth-ranking risk factor for mortality globally1. Racial/ethnic minorities and lower-income groups in the USA are at a higher risk of death from exposure to PM2.5than are other population/income groups2–5. Moreover, disparities in exposure to air pollution among population and income groups are known to exist. Here we develop a data platform that links demographic data (from the US Census Bureau and American Community Survey) and PM2.5 data across the USA. We analyse the data at the tabulation area level of US zip codes (Nis approximately 32,000) between2000 and 2016. We show that areas with higher-than-average white and Native American populations have been consistently exposed to average PM2.5 levels that are lower than areas with higher-than-average Black, Asian and Hispanic or Latino populations. Moreover, areas with low-income populations have been consistently exposed to higher average PM2.5 levels than areas with high-income groups for the years 2004–2016. Furthermore, disparities in exposure relative to safety standards set by the US Environmental Protection Agency and the World Health Organization have been increasing over time. Our findings suggest that more-targeted PM2.5reductions are necessary to provide all people with a similar degree of protection from environmental hazards. Our study is observational and cannot provide insight into the drivers of the identified disparities.