Low concentrations of air pollution that are within federal safety limits were linked with an increased risk of death among elderly people, including vulnerable subgroups. Tens of thousands of deaths over a 17-year period could be attributed to small increases in annual air pollution concentrations.
The study will be published October 7, 2021, in The Lancet Planetary Health.
«We found that among elderly patients enrolled in Medicare, small increases in long-term exposure to both particle and gaseous air pollutants increased the risk of death, even at levels deemed safe by current regulations,» said lead study author Mahdieh Danesh Yazdi, a postdoctoral fellow in Harvard Chan School’s Department of Environmental Health. «Our findings suggest that current air pollution limits are not adequate to protect the health of vulnerable groups.»
Previous studies have suggested that people exposed to air pollution concentrations that are lower than those permitted by the U.S. Environmental Protection Agency may still have an increased risk of illness and mortality. But most earlier studies didn’t focus on individuals who were continually exposed to lower concentrations of pollutants during the study period, as the new study does. Researchers also used a robust causal modeling technique and a large dataset for their analysis that gave them enough power to detect links between air pollution and mortality in demographic and socioeconomic subgroups.
The analysis included data on millions of Medicare enrollees from 2000 to 2016. The researchers predicted people’s exposure levels by using satellite-based measurements, land-use data, meteorological data, and chemical-transport models to generate daily air pollution predictions as well as annual averages of exposure levels across the U.S. Participants were assigned exposures based on their residential postal codes. The researchers adjusted for factors such as age, sex, race, education level, and smoking history.
The study looked at the effects of three different types of pollutants, including fine particulate matter, or PM2.5 — particulates with a diameter of less than 2.5 micrograms per cubic meter of air (?g/m3) — nitrogen dioxide (NO2), and summer ozone (O3). The researchers limited their dataset to individuals who were exposed to air pollution concentrations below the annual maximums recommended by the EPA. For PM2.5, the threshold is 12 ?g/m3; for NO2, it’s 53 parts per billion (ppb). There is no regulation regarding long-term exposure for O3, so the researchers chose 50 ppb as an upper exposure limit for the purposes of the study.
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