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As summer approaches, many people will be turning to their weather apps to check the air quality. A green dot usually means the air is good, at levels deemed safe by the Environmental Protection Agency (EPA). But a new study from the University of Mississippi found that contamination levels well below the agency’s regulatory guidelines can still pose a risk to human health.
Researchers at the University of Mississippi analyzed decades of scientific literature examining how low levels of PM2.5 (particulate matter produced by traffic, industry, and smoke) affect cardiovascular health. Specifically, we looked at papers that evaluated pollution levels that fall within the EPA’s established pollution levels, currently capped at 9 micrograms per cubic meter per year.
Reviews published in environmental pollutionfound that of 95 studies analyzed from around the world, 67% showed a significant association with cardiovascular problems. Focusing specifically on the most adverse outcomes, 76% of studies focused on major events such as stroke and cardiovascular death found a significant association with low-level contamination.
Researchers at the University of Mississippi believe the EPA should reevaluate its current standards based on their results. “If we are going to create regulations that focus solely on human health, our review suggests they should be lowered because of the confirmed cardiovascular effects,” lead author Courtney Roper, assistant professor of environmental toxicology, said in a press release.
Research shows that vulnerable populations, including the elderly, young children, and people with a history of cardiovascular events, are at higher risk of PM2.5-related health effects even at low levels. Additionally, people of low socioeconomic status and non-white people were also found to be particularly at risk.
“The risk also depends on the source of PM2.5,” said study co-author James Stewart, associate professor of pharmacology at the University of Mississippi. “Whether it’s traffic pollution, manufacturing pollution, or even rural pollution where harvesting and tillage generate dust, it can impact human health on so many levels,” Stewart said in a press release.
The findings don’t surprise Dr. Philip Landrigan, a pediatrician and epidemiologist at Boston University who was not involved in the study. He pointed to the fact that the EPA’s annual standard for PM2.5 is nearly twice the average annual level of 5 micrograms per cubic meter recommended by the World Health Organization (WHO).
Regarding daily exposure to PM 2.5, the WHO recommends a limit of 15 micrograms per cubic meter, which is less than half the EPA limit of 35 micrograms. Daily limits have been set higher to account for temporary spikes.
“We know from well-conducted medical and epidemiological studies that even below the WHO guideline of 5, there is still some risk,” Landrigan said. “Obviously the lower the air pollution level, the lower the risk, but almost any level of air pollution, up to near zero, carries some risk.”
Still, Landrigan believes some of the worst health consequences can be avoided if the WHO’s annual standards are implemented. “This would prevent many of the deaths from heart disease and stroke that currently occur at the legally permissible level of 9 micrograms.”
The findings come at a critical time for U.S. air pollution policy. Back in April, several states sued the EPA for failing to comply with clean air limits. A coalition of environmental and health groups, including the American Lung Association, has also filed its own lawsuit to force government agencies to comply.
“EPA does not comment on external studies that are independent of the agency’s National Air Quality Standards (NAAQS) review process,” EPA wrote in response to the study’s findings.
Landrigan believes the United States has reached a breaking point when it comes to safe air regulations.
“We’re at a point where we know more about the dangers of low-level air pollution. Levels that were once considered safe are now known to be unsafe,” he said. “It’s certainly time for a paradigm shift, and it’s time to lower air pollution standards again. It may not happen this year, but I think we’ll see those reductions in the next few years.”
Featured image: AC for Unsplash+
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Julie Zenderoudi is an editorial intern at The New Lede. She is a Brooklyn-based science journalist and master’s student in New York University’s Science, Health, and Environmental Reporting Program (SHERP). She previously worked for Canada’s public broadcaster CBC News, producing interview segments and commentary videos for the national broadcaster. Her work has appeared in Slate, Offrange, Prism, The Brooklyn Paper, and more.
