The 2020 California wildfire season was reported as the worst in California history, although the 2021 season is similar so far. The August Complex Fire in northern California and the Bobcat Fire in southern California were analyzed for pollutant emissions from smoke produced by the fires. The case studies explored how air pollution concentrations were affected by wildfire smoke using the Environmental Protection Agency’s (EPA) daily pollutant data. After utilizing the CalFire database to determine the timeframe and acreage burned during the fires, changes in the concentration of PM2.5, PM10, and ozone during the peak of each respective fire were studied. Air pollution concentrations were compared to the same time period in 2017, 2018, and 2019 for counties in California impacted by pollution from the wildfires. The Hybrid single particle Lagrangian integrated trajectory (HYSPLIT) model was used in conjunction with the NASA Earthview satellite to determine the counties most impacted by the fires, as well as the extent to which smoke travelled throughout North America. Counties in both northern and southern California experienced critically high concentrations of PM2.5, as high as 350 µg/m3 in northern California and 80 µg/m3 in southern California, during the peak of the fires. For both fires the percent changes in pollutant concentrations for PM2.5, PM10, and ozone (comparing 2017-2019 to 2020) showed up to an increase of 625% for 2020. Overall, significant increases in concentration levels for PM2.5, PM10, and ozone were measured across both fires in the majority of counties observed. HYSPLIT trajectories analysis showed that smoke from California wildfires disrupted other western US states such as Nevada, Idaho, and even as far as Montana for the August Complex Fire and as far as Mexico and parts of the Pacific Ocean for the Bobcat Fire.

Not just a blaze: The impact of air pollution on the California wildfire season

ACS Spring 2022

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