Mortality attributable to PM2.5 from wildland fires in California from 2008 to 2018

Abstract

In California, wildfire risk and severity have grown substantially in the last several decades. Research has characterized extensive adverse health impacts from exposure to wildfire-attributable fine particulate matter (PM_2.5), but few studies have quantified long-term outcomes, and none have used a wildfire-specific chronic dose-response mortality coefficient. Here, we quantified the mortality burden for PM_2.5 exposure from California fires from 2008 to 2018 using Community Multiscale Air Quality modeling system wildland fire PM_2.5 estimates. We used a concentration-response function for PM_2.5, applying ZIP code-level mortality data and an estimated wildfire-specific dose-response coefficient accounting for the likely toxicity of wildfire smoke. We estimate a total of 52,480 to 55,710 premature deaths are attributable to wildland fire PM_2.5 over the 11-year period with respect to two exposure scenarios, equating to an economic impact of $432 to $456 billion. These findings extend evidence on climate-related health impacts, suggesting that wildfires account for a greater mortality and economic burden than indicated by earlier studies.

Fig. 1.. CMAQ average daily fire-only PM_2.5 concentrations (μg/m³).

The data are at a 12-km resolution for 2008 to 2018, and the average value for all years is also presented. These are computed as the average over all days in each 12-km grid cell in each time period.

Fig. 2.. Summary of long-term mortality impacts across California due to fire-only PM_2.5.

This represents total deaths attributable to fire-only PM_2.5 for adults ages 25+. These were estimated using wildfire-specific (left) and undifferentiated (right) chronic dose-response values and are presented for 2008 to 2018. Base case, no modeled PM_2.5 concentrations are capped; mod cap, modeled PM_2.5 concentrations are capped at the 99.9th percentile value of all fire-only concentrations.

Fig. 3.. Total deaths attributable to fire-only PM_2.5 (base case).

This is depicted for the year with the fewest deaths attributable to wildland fire (2010), most deaths attributable to wildland fire (2018), and the annual average over the 11-year period (2008 to 2018). Darker colors indicate that more deaths occurred in a given ZIP code, and white areas are outside of ZIP code designations.

Fig. 4.. Economic valuation of mortality impacts from wildland fires.

These are presented alongside 95% CIs for the base case and mod cap scenarios, using the wildfire-specific dose-response value (β_WL; 2015 dollars, 3% discount rate, and 2015 income year).