The Environmental Protection Agency (EPA)'s standards for particulate-matter pollution may not be strict enough to protect public health, according to a recent study by researchers at the Harvard T.H. Chan School of Public Health.
The study, led by professor of environmental epidemiology Joel Schwartz, found that exposure to fine-particle pollution—usually measured by PM2.5 (particles 2.5 microns or less in diameter)—is “unambiguously” associated with higher death rates even when that pollution is below the EPA standards. Specifically, each 10µg/m3 (10 micrograms per cubic meter) increase in particulate matter concentration led to a 7.52 percent increase in mortality in New England.
“That’s a big deal,” said Schwartz, who is also an associate professor of medicine at Harvard Medical School. “Cancer is probably the cause of 20 percent of all deaths in New England. So that means if we get rid of air pollution, it would be as good as curing a third of cancers.” And, he pointed out, scientists may not yet be able to cure certain types of cancer, but current technology does permit a significant lowering of air-pollution levels. Adoption of such technology, however, is often thwarted by financial concerns. “Now imagine someone saying: ‘We have a cure for lung cancer and breast cancer, but we will not use it because it will cost people money,’” he added. “No one would buy that.”
The researchers measured the PM2.5 levels in every zip code in New England, and matched the results with health data of the 2.4 million people in the area who are covered by Medicare. Experts say that what distinguishes this study is its innovative use of satellite data—obtained from the National Aeronautics and Space Administration—to measure pollution levels. Usually, such data is obtained from on-the-ground monitors; that coverage is limited to urban areas. The satellite data, on the other hand, allowed researchers to observe particle levels in rural areas as well.
Daniel Jacob, Vasco McCoy Family professor of atmospheric chemistry and environmental engineering, said the study’s most important implication is that the current EPA standards may be too loose to protect public health. Under the Clean Air Act, the EPA must establish emission standards that require the maximum degree of reduction, review those standards periodically and, if necessary, revise them. The agency’s PM2.5 standards have been revised several times since they were first issued in 1997.
For the latest revision, in 2012, the EPA lowered its primary annual PM2.5 standard (the maximum average level of fine-particle pollution in a year) from 15µg/m3 to 12µg/m3, though it retained the daily standard (the maximum average level of fine-particle pollution in a 24-hour period) of 35µg/m3. The agency projects that 99 percent of U.S. counties with monitors will meet the annual standard of 12µg/m3 in 2020.
In light of his new findings and current realities, though, Schwartz recommends lowering the annual standard to 10µg/m3 and the daily standard to below 25µg/m3, though there is no clear threshold below which air pollution would be safe. The lower, the better, he said. “Given that a fairly large part of the U.S. has annual average PM concentrations below 10, there’s no reason why that’s not achievable,” he asserted. Once states have met the agency’s current requirements, he added, they have little incentive to clean their air further under current laws.
Schwartz, who worked for the EPA as a senior scientist from 1990 to 1994 (and as staff scientist from 1979 to 1987), said that the process of setting pollution standards is complex and often mired in politics. Industries lobby heavily for laws that would prevent further tightening. He suggested that the 2012 revision was strategically timed to take place after, rather than before, that year’s presidential election, because President Obama needed support in Ohio, a state with an extensive coal industry.
Because revisions to EPA pollution standards are informed by a review of literature in the field, explained HSPH’s senior associate dean for research Francesca Dominici, decisions to lower them are the result of rigorous epidemiological studies like the one Schwartz and his team conducted.
“We are very glad to get this out in time to be one of the studies that they consider in deciding whether they need to tighten the standard some more,” Schwartz said. “Low-Centration PM2.5 and Mortality: Estimating Acute and Chronic Effects in a Population-Based Study” was published online in Environmental Health Perspectives on June 3.
For more on fine particle pollution and how it affects health, read the Harvard Magazine feature “Clearing the Air”; for a report including an assessment of the cost-benefits of controlling air pollution, see “Clean Air, Longer Life.”
