Using a Statistical Model to Estimate the Effect of Wildland Fire Smoke on Ground Level PM2.5 and Asthma in California, USA

Forest fire activity has been increasing in California. Satellite imagery data along with ground level measurements of PM2.5 have been previously used to determine the presence and level of smoke. In this study, emergency room visits for asthma are explored for the impacts of wildland smoke over the entire state of California for the years 2008-2015. Smoke events included extreme high-intensity fire and smoke along with low and moderate smoke events. The presence of wildland fire smoke detected by remote sensing significantly increased fine particulate matter (PM2.5) and significantly increased the odds of exceeding expected concentrations of PM2.5 at ground level. Smoke observed above a monitoring site increases the chance of PM2.5 exceeding 35 mu g m(-3) (odds ratio 114 (87-150) when high levels of smoke are detected). The strength of association of an asthma emergency room visit is increased with higher PM2.5 concentrations. The odds ratios (OR) are highest for asthma hospital visits when daily mean PM2.5 concentrations experienced exceed 35 mu g m(-3) for multiple days (OR 1.38 (1.21-1.57) with 3 days). Nonetheless, on days with wildland fire smoke, the association of an emergency room visit for asthma due to PM2.5 is not observed. Further study is needed to confirm these findings and determine if this is a product of smoke avoidance and reduction of personal exposure during smoke episodes.