California Air Resources Board

Principal Investigator/Author(s): Guangquan (Jason) Su

Contractor: University of California, Berkeley

Contract Number: 22RD011

Project Status: Active

Relevant CARB Programs: Research Planning, Health & Exposure

Topic Areas: Health & Air Pollution

Research Summary:

Despite substantial improvement in air quality over the past two decades, fine particulate matter (PM_2.5) remains a critical environmental health concern in California. Although many studies have estimated mortality risks from PM_2.5, relatively few provide life-expectancy estimates, and limited studies have been conducted on how impacts differ across age and race-ethnicity groups. No prior study has also examined how the distribution of PM_2.5 impacts changes over time. In this project, the researchers quantified PM_2.5-attributable mortality and life-expectancy impacts for 2000–2010 (Period 1) and 2011–2021 (Period 2) in California, linking two decades of statewide mortality data to high-resolution exposure surfaces. 

While long-term PM2.5 exposure remained a significant factor of mortality in both decades, life-expectancy impacts statewide declined from 0.61 to 0.37 years, demonstrating that reductions in ambient PM2.5 resulted in significant reductions in mortality burden. The mortality and life expectancy findings in the study provide robust results to support the health value of CARB’s programs to reduce ambient PM2.5. When comparing the two periods across different race-ethnicity and age groups, Black and Hispanic populations experienced the largest reductions in life-expectancy losses, approximately 0.59 and 0.57 years, respectively.  Overall, in Period 1, older adults generally had higher PM2.5 impacts for most race-ethnicity groups. In Period 2, younger and middle-aged groups had higher impacts. These higher impacts in younger and middle-aged groups are impacted by a demographic shift from increased population size and show the influence of other occupational and community exposures. The exposure sources for these younger groups should be targeted to achieve equitable exposure and health impacts for all age groups in California.

The results from census tract analysis confirm that statewide progress reduced PM2.5-related death burdens but also showed persistent local disparities reflecting differences in sources and historically elevated exposure patterns in these areas. Together, these findings provide a clearer understanding of how PM2.5 mortality impacts have evolved in California, where policy progress has achieved the largest gains, and where residual disparities remain. The results provide CARB with strong support for statewide regulatory strategies and the need for continued and targeted equity-focused interventions to address remaining PM2.5-related mortality risks.

Keywords: particulate matter (PM), communities, exposure impacts, mortality, life expectancy, racial-ethnicity