PM2.5-Attributable Toxicity: How sensitive are mortality estimates to different concentration-response functions?

Epidemiologic studies have consistently observed associations between fine particulate matter (PM2.5) exposure and toxic health effects, such as premature mortality. Health impact assessments typically use a single log-linear CR function per health outcome to estimate counts of avoided human health effects resulting from air quality improvements. In the future, PM2.5 air quality concentrations are estimated to decrease, while the population is expected to increase. These countervailing changes make predicting total aggregated mortality burden fluctuations in the U.S. over time challenging. This project estimates the PM2.5-attributable toxicity, in the form of premature mortality burden, using a variety of CR functions from the epidemiology literature that relate all-cause or non-accidental mortality to long-term (i.e., more than one year) PM2.5 exposures among the U.S. population. We then further evaluate the variability of premature mortality estimates to stratification by potentially more susceptible populations (e.g., race and ethnicity) and exposure level (above or below certain thresholds, such as, 12 µg/m3, the current annual NAAQS for PM2.5). We find that unstratified annual adult mortality burden incidence estimates exhibit substantial (e.g., ~3-fold) variability. In addition, future mortality burden estimates stratified by race/ethnicity are larger than the unstratified estimates of the entire population, likely due to increasing proportions of people/communities of color increases. Studies that stratify PM2.5-attributable mortality HRs by an exposure concentration threshold led to substantially higher estimates. As mortality impacts constitute vast majority of economic benefits for air pollution regulations, these results are intended to provide transparency regarding the sensitivity of mortality estimates to upstream input choices.   Disclaimer: Views expressed here do not necessarily reflect official views of the U.S. EPA or the federal government.

Impact/Purpose

The published manuscript referenced by this abstract asks how estimates of mortality are impacted across exposure models and hazard ratios derived from various high-quality epidemiologic studies. As mortality impacts constitute the vast majority of economic benefits for air pollution regulations, these findings to be of interest to both scientists and the public.

Citation

Chan, E., N. Fann, AND J. Kelly. PM2.5-Attributable Toxicity: How sensitive are mortality estimates to different concentration-response functions? 2024 Annual Society of Toxicology Meeting, Salt Lake, UT, March 10 - 14, 2024.

• SOT POSTER 2024_CHAN.PDF (PDF)  (NA  pp, 472.9 KB, about PDF)