Since the beginning of the COVID-19 pandemic, due to the spread of SARS-CoV-2 virus, there has been a scientific debate regarding the role of airborne transmission due to respiratory aerosols released by infected individuals (Prather et al., 2020; Belosi et al., 2021). This mechanism of transmission could be more relevant in indoor environments compared to outdoors, especially in small and poorly ventilated rooms. Consequently, there is a need to understand the efficiency of the restriction policies enforced to limit the risks, especially in indoor community environments. One of the key parameters to ascertain the risks of airborne transmission is the concentrations of SARS-CoV-2 genetic material (RNA) in air. This work investigates this aspect in both outdoor and indoor environments in different towns of Italy. Outdoor samples were collected using both PM10 lowvolume (2.3 m3/h) samplers for 48h in parallel in Venice (Veneto region, north-east of Italy) and Lecce (Puglia region, south-east of Italy) during the first wave of pandemic (Fig. 1). In addition, two samples for each site, were collected using MOUDI multistage impactors (1.8 m3/h for six days sampling) able to separate 12 size ranges from nanoparticles (diameter D<0.056 ?m) up to coarse particles (D>18 ?m). During the maximum spread of second wave of pandemic in Italy, between end of November and end of December 2020, air samples were collected in different community indoor environments: one train station and two food markets in metropolitan city of Venice (Veneto Region); one canteen in Bologna (Emilia-Romagna region, central Italy); one shopping centre, one hair salon, and one pharmacy in Lecce (Puglia region). In this period there were restrictions on the maximum quota of customer entries in indoor environments and the compulsory use of facemasks. All collected samples were analysed to individuate the presence of SARS-CoV-2 RNA traces using two independent approaches: real-time RT-PCR and ddPCR (Chirizzi et al., 2021). Recovery tests done using Mengo virus strain MC0 indicates a recovery of about 50% with the procedure used. Modelling of expected average concentrations in the different environments, were also done using influx of customers data and local epidemiological information to compare with measurements. Results show a negligible risk for airborne transmission in outdoor, excluding eventually crowed areas. In community indoor environments investigated, the restrictive policies enforced effectively reduced the risk of airborne transmissions, providing that physical distance is respected. Indoor ventilation plays an important role in reducing concentrations of virus-laden particles. The work was done in the framework of project AIR-CoV (Evaluation of the concentration and size distribution of SARS-CoV-2 in air in outdoor and indoor environments). References: Belosi, F. Conte, M., Gianelle, V., Santachiara, G., Contini, D., 2021. On the concentration of SARS-CoV-2 in outdoor air and the interaction with pre-existing atmospheric particles. Environmental Research 193, 110603. Chirizzi, D., Conte, M., Feltracco, M., Dinoi, A., Gregoris, E., et al., 2020. SARS-CoV-2 concentrations and virusladen aerosol size distributions in outdoor air in north and south of Italy. Environ. Int. 146, 106255. Prather, K.A., Wang, C.C., Schooley, R.T., 2020. Reducing transmission of SARS-COV-2. Science. https://doi.org/10.1126/science.abc6197.
Measurements of SARS-CoV-2 concentrations in indoor and outdoor air in Italy: implications for airborne transmission
M Conte;M Feltracco;S Trabucco;A Dinoi;E Gregoris;E Barbaro;F Belosi;D Contini
2021
Abstract
Since the beginning of the COVID-19 pandemic, due to the spread of SARS-CoV-2 virus, there has been a scientific debate regarding the role of airborne transmission due to respiratory aerosols released by infected individuals (Prather et al., 2020; Belosi et al., 2021). This mechanism of transmission could be more relevant in indoor environments compared to outdoors, especially in small and poorly ventilated rooms. Consequently, there is a need to understand the efficiency of the restriction policies enforced to limit the risks, especially in indoor community environments. One of the key parameters to ascertain the risks of airborne transmission is the concentrations of SARS-CoV-2 genetic material (RNA) in air. This work investigates this aspect in both outdoor and indoor environments in different towns of Italy. Outdoor samples were collected using both PM10 lowvolume (2.3 m3/h) samplers for 48h in parallel in Venice (Veneto region, north-east of Italy) and Lecce (Puglia region, south-east of Italy) during the first wave of pandemic (Fig. 1). In addition, two samples for each site, were collected using MOUDI multistage impactors (1.8 m3/h for six days sampling) able to separate 12 size ranges from nanoparticles (diameter D<0.056 ?m) up to coarse particles (D>18 ?m). During the maximum spread of second wave of pandemic in Italy, between end of November and end of December 2020, air samples were collected in different community indoor environments: one train station and two food markets in metropolitan city of Venice (Veneto Region); one canteen in Bologna (Emilia-Romagna region, central Italy); one shopping centre, one hair salon, and one pharmacy in Lecce (Puglia region). In this period there were restrictions on the maximum quota of customer entries in indoor environments and the compulsory use of facemasks. All collected samples were analysed to individuate the presence of SARS-CoV-2 RNA traces using two independent approaches: real-time RT-PCR and ddPCR (Chirizzi et al., 2021). Recovery tests done using Mengo virus strain MC0 indicates a recovery of about 50% with the procedure used. Modelling of expected average concentrations in the different environments, were also done using influx of customers data and local epidemiological information to compare with measurements. Results show a negligible risk for airborne transmission in outdoor, excluding eventually crowed areas. In community indoor environments investigated, the restrictive policies enforced effectively reduced the risk of airborne transmissions, providing that physical distance is respected. Indoor ventilation plays an important role in reducing concentrations of virus-laden particles. The work was done in the framework of project AIR-CoV (Evaluation of the concentration and size distribution of SARS-CoV-2 in air in outdoor and indoor environments). References: Belosi, F. Conte, M., Gianelle, V., Santachiara, G., Contini, D., 2021. On the concentration of SARS-CoV-2 in outdoor air and the interaction with pre-existing atmospheric particles. Environmental Research 193, 110603. Chirizzi, D., Conte, M., Feltracco, M., Dinoi, A., Gregoris, E., et al., 2020. SARS-CoV-2 concentrations and virusladen aerosol size distributions in outdoor air in north and south of Italy. Environ. Int. 146, 106255. Prather, K.A., Wang, C.C., Schooley, R.T., 2020. Reducing transmission of SARS-COV-2. Science. https://doi.org/10.1126/science.abc6197.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
