The association between daily-diagnosed COVID-19 morbidity and short-term exposure to PM₁ is larger than associations with PM_2.5 and PM₁₀

Exposure to particulate matter (PM) could increase both susceptibility to SARS-CoV-2 infection and severity of COVID-19 disease. Prior studies investigating associations between PM and COVID-19 morbidity have only considered PM_2.5 or PM₁₀, rather than PM₁. We investigated the associations between daily-diagnosed COVID-19 morbidity and average exposures to ambient PM₁ starting at 0 through 21 days before the day of diagnosis in 12 cities in China using a two-step analysis: a time-series quasi-Poisson analysis to analyze the associations in each city; and then a meta-analysis to estimate the overall association. Diagnosed morbidities and PM₁ data were obtained from National Health Commission in China and China Meteorological Administration, respectively. We found association between short-term exposures to ambient PM₁ with COVID-19 morbidity was significantly positive, and larger than the associations with PM_2.5 and PM₁₀. Percent increases in daily-diagnosed COVID-19 morbidity per IQR/10 PM₁ for different moving averages ranged from 1.50% (−1.20%, 4.30%) to 241% (95%CI: 80.7%, 545%), with largest values for exposure windows starting at 17 days before diagnosis. Our results indicate that smaller particles are more highly associated with COVID-19 morbidity, and most of the effects from PM_2.5 and PM₁₀ on COVID-19 may be primarily due to the PM₁. This study will be helpful for implementing measures and policies to control the spread of COVID-19.