Risk analysis of different transport vehicles in India during COVID-19 pandemic

Due to the airborne nature of viral particles, adequate ventilation has been identified as one suitable mitigation strategy for reducing their transmission. While 'dilution of air by opening the window' has been prescribed by national and international health agencies, unintended detrimental consequences might result in many developing countries with high ambient air pollution. In the present study, PM_2.5 exposure concentration and probability of mortality due to PM_2.5 in different scenarios were assessed. A COVID airborne infection risk estimator was used to estimate the probability of infection by aerosol transmission in various commuter micro-environments: (a) air conditioned (AC) taxi (b) non-AC taxi (c) bus and (d) autorickshaw. The following were the estimated exposure concentrations in the four types of vehicles during pre-lockdown, during lockdown, and lost-lockdown: AC taxi cars (17.16 μg/m³, 4.52 μg/m³, and 25.09 μg/m³); non-AC taxis: (28.74 μg/m³, 7.56 μg/m³, 42.01 μg/m³); buses (21.79 μg/m³, 5.73 μg/m³, 31.86 μg/m³) autorickshaws (51.30 μg/m³, 3.50 μg/m³, 75 μg/m³). Post-lockdown, the probability of mortality due to PM_2.5 was highest for autorickshaws (5.67 × 10^-3), followed by non-AC taxis (2.07 × 10^-3), buses (1.39 × 10^-3), and AC taxis (1.02 × 10^-3). This order of risk is inverted for the probability of infection by SARS-COV-2, with the highest for AC taxis (6.10 × 10^-2), followed by non-AC taxis (1.71 × 10^-2), buses (1.42 × 10^-2), and the lowest risk in autorickshaws (1.99 × 10^-4). The findings of the present study suggest that vehicles with higher ventilation or air changes per hour (ACH) should be preferred over other modes of transport during COVID-19 pandemic.