March 29, 2017 – Current limits on fine particulate matter in the air set by the U.S. Environmental Protection Agency (EPA) may not be sufficient to protect elderly people from the risk of premature death from air pollution, according to a large study from Harvard T.H. Chan School of Public Health.
Looking at 13 years’ worth of data from more than 13 million elderly people living in the Southeastern U.S., the new study, published in Epidemiology, found that for each 1 µg m-3 (roughly 10%) increase in the annual average concentration of PM2.5 (particles smaller than 2.5 microns in diameter) in the air in a particular region, mortality risk rose by 2%. The risk showed up even in areas where PM2.5 levels were below current EPA limits.
“We found that if particle concentrations could be reduced by about 10%, it would lower the death rates of people age 65 and older in the Southeastern U.S., saving 7,000 to 10,000 lives per year,” said Joel Schwartz, professor of environmental epidemiology and senior author of the study. “That would be a very large public health impact.”
While the link between long-term exposure to PM2.5 and increased mortality risk has been well documented over the past two decades, previous studies included mostly participants with high socioeconomic status, making it difficult to identify air pollution’s effects on those who are socially and economically disadvantaged. The new study looked at the entire Medicare-eligible population of seven Southeastern states— Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, and Tennessee. It also took a closer look at characteristics that potentially put people at greater risk from air pollution, such as diabetes, race, and socioeconomic status.
“In addition to showing what is happening to the general population in that region, our study also allowed us to look at whether less-advantaged groups were more susceptible to particulate exposure,” Schwartz said.
The researchers used a novel model, based on both satellite remote sensing and on-the-ground pollution monitoring, to predict pollution in the zip code of each participant, and compared the pollution data with Medicare data on participants’ health.
The researchers found that people who were either black, eligible for Medicaid, lived in lower-income zip codes, or had chronic diseases were more susceptible to particulate air pollution. “In other words, these groups had larger increases in death rates when PM2.5 particulates increased than people not in these categories,” said Schwartz.
The toxicity of PM2.5 particulates increased when average summer temperatures increased, according to the study. Particles from traffic were found to be more toxic than other types, indicating a need for further reductions from vehicle pollution.
“Our findings provide a range of factors that modify people’s susceptibility to long-term PM2.5 exposure, and could be used to assess the risk of long-term air pollution and to protect vulnerable populations,” said lead author Yan Wang, a doctoral student.