Air pollution, particularly fine and ultrafine particulate matter aerosols, underlies a wide range of communicable and non-communicable disease affecting many systems including the cardiopulmonary and immune systems, and arises primarily from transportation and industry. A number of air pollution driven diseases also are Covid19 comorbidities. Thus, a number of studies on air pollution exposure, particularly particulate matter, strongly indicate air pollution is an important underlying factor in Covid19 transmission, severity, and mortality. This suggests that air pollution from natural sources, particularly wildfires, could play a role in the Covid19 pandemic. We tested this hypothesis on three wildfire smoke events in Orange County, CA, each of which was followed by Covid19 case increases after an approximately one-week lag. This lag was consistent with combined incubation time and testing/reporting times. Moreover, the three events suggest a dose dependency. The wildfire comorbidity hypothesis implies that at-risk-populations should reduce smoke exposure from wildfires, as well as indoors from biomass burning for heating, cooking, and aesthetic purposes.
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