An Ecological Study to Investigate Links Between Atmospheric Pollutants From Farming and SARS-CoV-2 Mortality

Exposure to atmospheric particulate matter and nitrogen dioxide has been linked to SARS-CoV-2 infection and death. We hypothesized that an interaction between SARS-CoV-2 infection and exposure to farming-related atmospheric pollutants worsens the effect of SARS-CoV-2 on mortality. Our objective was investigate this hypothesis by performing an ecological study in five Italian Regions (Piedmont, Lombardy, Veneto, Emilia-Romagna and Sicily) linking all-cause mortality, by province (administrative entities within regions), to atmospheric particulate matter (PM2.5 and PM10) nitrous oxide (N2O), ammonia (NH3) and methane (CH4) mainly produced by agricultural activities. Study outcome was change in all-cause mortality during March-April 2020, compared to March-April 2015-2019 (period) as assessed by mortality rate ratios (MRRs) estimated using multivariate negative binomial regression models that adjusted for air temperature, humidity and population density. The MRR for the interaction of period with NH3 exposure, considering all pollutants together was 1.133, equivalent to a 13.3% increase in mortality over and above that due to period (proxy for COVID-19 mortality) for each ton/km2 increase in NH3 emissions. Although the study was ecological, and did not provide evidence of a causal link between SARS-CoV-2 and farming-related pollutants, in accord with the precautionary principle we recommend application of measures to limit NH3 exposure particularly while the COVID-19 pandemic continues.