Vulnerability and burden of all-cause mortality associated with particulate air pollution increased during COVID-19 pandemic: a nationwide observed study in Italy

Ye, T.; Xu, R.; Yu, W.; Chen, Z.; Guo, Y.; Li, S.

Abstract Background: Limited evidence is available on the health effects of particulate matter (i.e. PM2.5, particulate matter with an aerodynamic diameter < 2.5m; PM10, < 10m; PM2.5-10, 2.5-10m) during the pandemic of COVID-19 in Italy. Objectives: To examine the associations between all-cause mortality and daily PM2.5, PM2.5-10, and PM10 in the pandemic period, and compare them to the normal periods (2015-2019) in Italy. Methods: We collected daily data regarding all-cause (stratified by age and gender), and PM2.5, PM2.5-10, and PM10 for 107 Italian provinces from 1, January 2015 to 31, May 2020. A time-stratified case-cross design with the distributed lag non-linear model was used to examine the association between PM and all-cause mortality during the first three months of the COVID-19 outbreak (March to May in 2020) and the same months in 2015-2019. We also compared the counts and fractions of death attributable to PM in two periods. Results: Overall, Italy saw an increase in daily death counts while slight decreases in PM concentrations in 2020 pandemic period compared to same months of 2015-2019. Mortality effects were significant in lag 0-3 days for PM2.5, lag 0-2 for PM10, and lag 0-1 for PM2.5-10. Each 10 g/m3 increase in PM was associated much higher increase in daily all-cause mortality during 2020 pandemic period compared to the same months during 2015-2019 [increased mortality rate: 7.24 % (95%CI: 4.84%, 9.70%) versus 1.69% (95%CI: 1.12%, 2.25%) for PM2.5; 3.45 % (95%C: 2.58%, 4.34%) versus 1.11% (95%CI: 0.79%, 1.42%) for PM10, 4.25% (95%CI: 2.99%, 5.52%) versus 1.76% (95%CI: 1.14%, 2.38%) for PM2.5-10]. The counts and fractions of deaths attributable to PM were higher in 2020 than the normal periods for PM2.5 (attributable death counts: 20,062 in 2020 versus 3,927 per year in 2015-2019; attributable fractions: 10.2% versus 2.4%), PM10 (15,112 versus 3,999; 7.7% versus 2.5%), and PM2.5-10 (7,193 versus 2303; 3.7% versus 1.4%). Conclusions: COVID-19 pandemic increased the vulnerability and excess cases of all-cause mortality associated with short-term exposure to PM2.5, PM2.5-10 and PM10 in Italy, despite a decline in air pollution level. This suggests using historical PM-mortality association to calculate health benefits associated with reduction in PMs has big uncertainties.