Air pollution linked to risk of premature death

Researchers knew the link between long-term exposure to air pollution and premature death, but short-term exposure may be dangerous, too. Kodda/iStock/Thinkstock

Poor air quality can make it hard to breathe—and it may take a few days for your body to recover. One type of air pollution is the fine particles (2.5 micrometers in diameter or less) from factories, power plants, and car exhaust. Another significant type is ozone, the main ingredient of urban smog. When you breathe in high levels of fine particles or ozone, your lungs can become irritated. Outdoor air pollution has been associated with asthma, heart attacks, strokes, and cancers.

Studies have shown an association between long-term exposure to air pollution and premature death. Public policies have helped to improve air quality in the United States and elsewhere. Experts periodically examine scientific analyses of air pollution levels and death and disease rates to reassess air quality standards.

A research team led by Dr. Francesca Dominici at Harvard T.H. Chan School of Public Health set out to estimate the risk of death in older adults from short-term exposures to air pollution. The team also investigated whether certain subgroups of the population may be particularly vulnerable. The study was supported by NIH’s National Institute of Environmental Health Sciences (NIEHS). Results appeared in JAMA on December 26, 2017.

The team used air pollution prediction models and artificial neural networks to estimate daily air pollution levels for more than 39,000 zip codes, even in unmonitored rural areas of the country. They then looked at pollution levels around the days of death for 22 million adults aged 65 and older based on death records from 2000 to 2012. The air pollution levels on the days of death (for 22 million deaths) were compared with pollution levels during other days (76 million control days).

The researchers found that when air pollution from either fine particles or ozone increased intermittently, there was a substantial increase in deaths within a 2-day period. Each intermittent, incremental increase of either 10 micrograms of fine particles per cubic meter or 10 parts per billion of ozone was associated with a rise in deaths.

The large dataset also enabled the research team to study effects by age, sex, race, age, and income level. Those most at risk of death associated with air pollution were over 85 years old, female, nonwhite, or economically disadvantaged.

“This [is] the most comprehensive study of short-term exposure to pollution and mortality to date,” Dominici says. “We found that the mortality rate increases almost linearly as air pollution increases. Any level of air pollution, no matter how low, is harmful to human health.”

Experts can use the results from studies of air pollution to assess whether air quality standards are sufficient to protect public health.

—by Geri Piazza