Particulate matter exposure has been associated with the appearance and severity of several diseases, including viral infections. The aim of this study was to investigate whether coronavirus disease 2019 (COVID-19) cases and deaths across Italian regions and provinces in March 2020 were linked to past exposure to fine and coarse particulate matter (namely, PM 2.5 and PM 10 , respectively). Material and methods: Geographical distributions of COVID-19 cases and deaths (105,792 and 12,428, respectively, up to 31 st March 2020), PM 2.5 and PM 10 exposure, and demographic characteristics were extracted from publicly accessible databases. Adjusted regression models were performed to test the association between particulate matter exposure in different Italian regions and provinces and COVID-19 incidence proportions and death rates. Results: A heterogeneous distribution of COVID-19 cases/deaths and particulate matter exposure was observed in Italy, with the highest numbers in Northern Italy regions and provinces. Independent associations between regional PM 2.5 /PM 10 exposure and COVID-19 incidence proportion and death rate were observed (COVID-19 incidence proportion: β = 0.71, p = 0.003, β = 0.61, p = 0.031, respectively; COVID-19 death rate: β = 0.68, p = 0.004 and β = 0.61, p = 0.029, respectively). Similarly, PM 2.5 /PM 10 exposures were independently associated with COVID-19 incidence proportion (β = 0.26, p = 0.024 and β = 0.27, p = 0.006, respectively) at the provincial level. The number of days exceeding the provincial limit value of exposure to PM 10 (50 µg/m 3) was also independently associated with the COVID-19 incidence proportion (β = 0.30, p = 0.008). Conclusions: Exposure to PM 2.5 and PM 10 is associated with COVID-19 cases and deaths, suggesting that particulate matter pollution may play a role in the COVID-19 outbreak and explain the heterogeneous distribution of COVID-19 in Italian regions and provinces.

Background Variable sex-disaggregated data on Coronavirus disease 2019 (COVID-19) incidence proportion (IP) have been reported in different datasets and studies. Factors explaining the inconsistent distribution of COVID-19 among sexes are still unclear. Objectives This study aimed to analyse time-related variation of sex-disaggregated COVID-19 IP in Italy since March 9 th to May 11 th 2020, and to test its association with the frequency of swab testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Study design Sex-disaggregated data on COVID-19 cases were collected from Italian publicly accessible databases along with undisaggregated data on the number of reverse transcriptase–polymerase chain reaction (RT-PCR) SARS-CoV-2 tests. Crude and adjusted associations between the frequency of RT-PCR SARS-CoV-2 testing and male-to-female (M/F) ratio of COVID-19 IP were performed. Results COVID-19 IP increased progressively in both sexes. Sex prevalence of COVID-19 IP reversed over time, with the M/F ratio of COVID-19 IP having passed from 1,73 to 0,91. The mean number of daily swabs for RT-PCR SARS-CoV-2 test increased progressively until reaching a plateau in the last three weeks of the study period. The M/F ratio of COVID-19 IP inversely correlated with the number of daily swabs for RT-PCR SARS-CoV-2 test (r = -0,87, p < 0.001), even after adjusting for the median age of COVID-19 cases (β = -0,66, p < 0,001). Conclusions Time-related changes of sex distribution of COVID-19 IP in Italy are strongly influenced by the number of swabs testing for SARS-CoV-2. Whether gender-related disparities in the access to the diagnosis of COVID-19 may explain such a result need to be explored.

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