Exploring the role of particulate matter as a carrier of SARS-CoV-2 in USA cities

Abstract:

Studies suggest an important role of the particulate matter (PM) in the COVID-19 pandemic, however there are few studies investigating the PM role in the transmission of the viruses, and none have accounted for the PM confounding role as indicator of social interaction and mobility. We investigate the relationships between COVID-19 cases and PM, focusing on the transmission role of the latter in early and late stages of the pandemic. For a selection of cities in the United States, we collected the daily reported new cases of COVID-19 (source: Johns Hopkins University Center database) as well as daily average PM concentration in two particle size ranges, <2.5 µm, and <10 µm (PM2.5 and PM10 respectively) (source: Worldwide COVID-19 Dataset from Air Quality Open Data Platform for particulate matter data). We extracted the relevant curve parameters of the accumulated cases time series for each city in two stages: an early stage before the first maximum of daily cases and a late stage after this first peak (i.e., the "second wave"). Then, we correlated the curve parameters obtained for each city with their PM concentrations for a range of time lags and accumulation windows. In order to assess the contribution of PM as virus carrier only and exclude a possible weight as indicator of social interaction/mobility, we have compared correlations performed with PM2.5 and PM10 as the latter’s sources are more directly related to social mobility. We found a strong and significant relationship between PM2.5 concentrations and the growth rates around the 5th and 14th days after the report of the infection. We estimate that the daily cases peak can advance 10-16 days due to a PM2.5 20µg/m³ increase. We conclude that PM2.5 is not a first order effect in the analysed cities; however, it plays a discernible role in the COVID-19 transmission.