The Impact of 2020 California Wildfires on Air Quality

The 2020 California wildfire season was reported as the worst in California history, yet the 2021 season is close to the size and scope of 2020 wildfires already. Two case studies explored how air pollution concentrations were affected by wildfire smoke using the Environmental Protection Agency’s (EPA) daily pollutant data. The August Complex Fire in northern California and the Bobcat Fire in southern California were examined for air pollutant emissions from smoke produced by the fires. After utilizing the CalFire database to determine the timeframe and acreage burned, concentrations of PM2.5, PM10, and ozone during the peak of each respective fire 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 NASA Worldview 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 change in pollutant concentrations for PM2.5, PM10, and ozone comparing 2017-2019 to 2020 ranged from -0.57% to over 1,000%. Overall, significant increases in air pollutant concentrations for PM2.5, PM10, and ozone were measured across both fires in most counties studied. HYSPLIT trajectory analyses showed that smoke from California wildfires disrupted other western US states such as Nevada, Idaho, and Montana for the August Complex Fire and Mexico and parts of the Pacific Ocean for the Bobcat Fire