The study drew on Medicare demographic and mortality data from more than 68 million Americans ages 65 and older. Calculations of yearly average pollution exposures came from multiple sources, including the EPA Air Quality System monitoring and satellite-derived data. The authors adjusted for many factors known to affect health, such as socioeconomic status, smoking, and body mass index. They developed several statistical models, all of which demonstrated similar results: between 2000 and 2016, death rates rose by 6% to 8% for each incremental increase in PM2.5 exposure.

Just how small were these increases in exposure to air pollution? Particle pollution is measured in micrograms per cubic meter of air (μg/m3). Each time exposure levels rose by 10 μg/m3, death rates also rose by 6% to 8%. Excess deaths occurred even at low levels of PM2.5 exposure (2.8 μg/m3), which is well below the current EPA standards cutoff. The study authors estimate that adjusting the cutoff down from the current level of 12 μg/m3 to 10 μg/m3 could save more than 143,000 lives over 10 years.

What are the limitations of this study?

One limitation is that the variety of data are compiled at different levels: the individual, zip code, and county level. For example, pollution exposure is estimated in clusters by zip code. Yet someone living near a highway may have higher exposure than another person living further from the highway in the same zip code.

Additionally, the groups with the lowest PM2.5 exposure most likely exclude many cities and include a higher proportion of rural areas. Rural areas tend to be less dense, have fewer air quality data points, and may have zip codes spanning greater distances. Details like these may affect the certainty of conclusions that can be drawn. Nonetheless, this study has many groundbreaking features with sound science.

Staying healthy: The bottom line

Air pollution is known to contribute to disease and death. Now we have more evidence suggesting that this is true even at low levels of pollution. Currently the U.S. is considering whether to adjust regulatory cutoffs for annual fine particulate matter pollution known as PM2.5 to protect human health.

But don’t wait. You can take steps described in my previous blog post to reduce your exposure (and contribution) to pollution, and thus your health risks. And some of these steps have the added benefit of combatting climate change and improving planetary health.

(Wynne Armand, M.D., is a contributor to Harvard Health Publications.)

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