Examining PM_2.5 concentrations and exposure using multiple models.

Area of Science:

• Environmental Science
• Public Health
• Atmospheric Chemistry

Background:

• Epidemiologic studies link fine particulate matter (PM2.5) exposure to adverse health outcomes.
• Accurate PM2.5 exposure assessment is crucial for public health research and policy.

Purpose of the Study:

• To investigate PM2.5 concentrations in 2011 and projected changes by 2028 using diverse exposure models.
• To assess PM2.5 exposure for the U.S. population, including four racial/ethnic groups.
• To evaluate the impact of on-the-books regulations on future PM2.5 concentrations.

Main Methods:

• Utilized nine PM2.5 concentration models: two chemical transport models (CTMs), two interpolation methods, one satellite-derived method, one Bayesian regression model, and three machine learning methods.
• Focused on annual predictions at 12-km resolution over the conterminous U.S., with sensitivity analyses at 1-km resolution.
• Employed two inequality metrics to analyze exposure differences among racial/ethnic groups.

Main Results:

• Models predicted broadly consistent PM2.5 concentrations, with higher levels in the eastern U.S. and greater variability in the West.
• Estimated a national average decrease of approximately 1 µg/m³ in PM2.5 concentrations between 2011 and 2028 due to emission changes.
• Projected that modeled emission reductions would decrease absolute exposure inequality among racial/ethnic groups on average.

Conclusions:

• Diverse PM2.5 exposure models show agreement in spatial patterns and population-weighted averages.
• On-the-books regulations are projected to reduce PM2.5 concentrations and improve air quality by 2028.
• Future emission reductions are expected to mitigate disparities in PM2.5 exposure across racial and ethnic groups.