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

BackgroundLimited evidence is available on the health effects of particulate matter (i.e. PM2.5, particulate matter with an aerodynamic diameter < 2.5μm; PM10, < 10μm; PM2.5-10, 2.5-10μm) during the pandemic of COVID-19 in Italy.ObjectivesTo examine the associations between all-cause mortality and daily PM2.5, PM2.5-10, and PM10in the pandemic period, and compare them to the normal periods (2015-2019) in Italy.MethodsWe collected daily data regarding all-cause (stratified by age and gender), and PM2.5, PM2.5-10, and PM10for 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.ResultsOverall, 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 µg/m3increase 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%).ConclusionsCOVID-19 pandemic increased the vulnerability and excess cases of all-cause mortality associated with short-term exposure to PM2.5, PM2.5-10and PM10in 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.