IJERPH, Vol. 19, Pages 10000: Initially High Correlation between Air Pollution and COVD-19 Mortality Declined to Zero as the Pandemic Progressed: There Is No Evidence for a Causal Link between Air Pollution and COVD-19 Vulnerability (International Journal of Environmental Research and Public Health)

Wu et al. found a strong positive association between cumulative daily county-level COVID-19 mortality and long-term average PM2.5 concentrations through September 2020. We replicate the result of Wu et al. and extend the analysis through May 2022. The association between PM2.5 concentration and cumulative COVID-19 mortality falls sharply after September 2020. Using the data from Wu et al.’s “updated_data” branch through May 2022, we find the effect of a 1 μg/m3 increase in PM2.5 associated with only a +0.603% mortality difference. The 95% CI of this difference is between −0.560% and +1.78%, narrow bounds that include zero, with the upper bound far below the Wu et al. estimate. Short-term trends in the initial spread of COVID-19, not a long-term epidemiologic association, caused an early correlation between air pollution and COVID-19 mortality.