Public Health Impact of Fine Particulate Matter (PM2.5) from Prescribed and Wildland Fires in California

Wildfires and the changing landscape of air pollution related health burden  Wildfires are a major sources of air pollution. Understanding emerging patterns of wildfire-related health burden, including identification of the most affected populations, is key to formulating an equitable public health response.  We characterized trends in fine particulate matter (PM2.5) related health burden across California residential ZIP codes (2008-2016), focusing on asthma, chronic obstructive pulmonary disease (COPD), and all-cause respiratory and cardiovascular emergency department (ED) visits and hospital admissions (HAs). Using previously developed PM2.5 surfaces to estimate exposure, we generated California-specific relative risk estimates for the associations between PM2.5 and the outcomes, and used these to estimate health burden rates attributable to PM2.5 and the PM2.5-attributed fraction of overall morbidity. Satellite-derived products were used to identify wildfire smoke-impacted days and compute burden rates attributable to PM2.5 on these days. Health burden and attributable fraction estimates were also disaggregated by year, demographic factors, and geographic factors.  An excess of 300,000 respiratory-related and 129,000 cardiovascular-related ED visits were attributed to PM2.5. The PM2.5 relative risks estimates for HAs were similar to ED visits for cardiovascular- and COPD-related outcomes but lower for asthma- and overall respiratory-related visits. The PM2.5-attributed burden decreased over the study period, whereas the fraction attributed to wildfire smoke varied by intensity of the fire season, comprising up to 17% of the total PM2.5-burden, an amount approximately equal to the average two-year reduction in total PM2.5-related burden observed over the study period. Disparities in PM2.5-burden were observed by age, race and ethnicity which reflected observed differences in underlying morbidity rates. The same disparities were observed for wildfire PM2.5-burden along with increased burden rates among the rural population and central and northern California. Wildfire activity in California threatens to offset the health benefits gained by improvements in air quality. These impacts disproportionately affect demographic groups and regions already experiencing poor air quality.  

Impact/Purpose

This manuscript aims to understand the changing patterns of population susceptibility to health effects and vulnerability to smoke exposure in California. Using daily records of emergency department visits and hospital admissions we characterized trends in health burden attributed to PM2.5 and wildfire smoke between 2008 and 2016. We used four cardiorespiratory outcomes previously associated with wildfire smoke and PM2.5 exposure (i.e., asthma, chronic obstructive pulmonary disease, respiratory disease, and cardiovascular disease). We estimated the association between each of the outcomes and daily variation in PM2.5 to derive California-specific health risk estimates and used these estimates to calculate excess health burden attributed to both total PM2.5 and PM2.5 on days affected by wildfire smoke. Health burden rates and attributable fractions were compared across years and by ZIP code, as well as by age, race/ethnicity, gender, urbanicity, and long-term air quality, to quantify temporal, geographic, and demographic trends.

Citation

Rappold, A. Public Health Impact of Fine Particulate Matter (PM2.5) from Prescribed and Wildland Fires in California. Classroom presentation, Raleigh, NC, March 23, 2023.