Detection of SARS-CoV-2 in the indoor air and surfaces of subway trains in Mashhad, Iran

Introduction Millions of passengers around the world are concerned with the possibility of SARS-CoV-2 contamination on public transportation. Therefore, this study aimed to investigate the presence of SARS-CoV-2 virus in indoor air and subway surfaces in Mashhad. Methods In this study, air and surface sampling were done at two times in the morning (7–8:30 a.m.) and evening (3:30–5 p.m.), simultaneously in two wagons for men and women in line 1 of Mashhad Metro in March 2021 to detect the virus and measure the concentration of particulate matter. Totally, 30 air and 30 metro samples were collected and examined by reverse transcriptase-polymerase chain reaction (RT-PCR). Results The results showed that three and two cases in the air and surface samples were infected with the SARS-CoV-2 virus, respectively. There was a significant relationship between the mean concentration of suspended particles PM 1 (particulate matter smaller than 1 μm) with PM 2.5 (particulate matter smaller than 2.5 μm) and PM 10 (particulate matter smaller than 10 μm) ( p < 0. 05). There was also a significant relationship between the mean concentration of suspended particles PM 2.5 and PM 10 . The results showed that the mean PM 2.5 measured in the indoor air of the Mashhad metro wagon had a significant relationship with WHO and US EPA and national standards, and its value was higher than the standards ( p < 0.05). The average particle concentrations of PM 1 , PM 2.5 , and PM 10 were equal to 40.46, 42.61, and 48.31 μg/m 3 . Conclusion According to the results of the pollution detected in this study, COVID-19 may be transmitted by air and environmental surfaces. Our study emphasizes the need for continuous assessment of the presence of the virus in public transportation. Detection of viral RNA in subways indicates the necessity of adequate disinfection in public settings, strictness in disinfection methods, strengthening of educational activities for sanitary measures, physical spacing plan, and increasing ventilation of wagons.