The association of COVID-19 pandemic with air quality in Bangkok was analyzed by correlation and regression analysis. The time-series data covered the infection outbreak period (January 2020 to February 2021). The first outbreak started with a Chinese tourist on January 12, 2020. The Thai government announced a lockdown of the city from 25 March -15 June 2020 which led to a reduction of infection as well as the concentration of criteria air pollutants considerably. The second outbreak took place from a Burmese worker and thereafter the infection per day spread very fast until mid-December 2020. There was no lockdown policy in the second outbreak but the situation eased up with time and the vaccines arrived in late February 2021. During the first peak outbreak (16 March – 17 May 2020) the rise of COVID-19 infection cumulative cases maintained a positive correlation with fine particulate matter, PM2.5 and PM10, with r values, 0.686 and 0.737 while carbon monoxide CO and ozone, O3 exhibited a negative correlation with r values, -0.416 and -0.261, respectively. For the first outbreak with the lockdown policy, the traffic-related air pollutants were decreasing and the gaseous pollutants were found a negative correlation with the cumulative cases. On the other hand, fine particulate matter can come from various sources including the trans-boundary aerosol therefore PM2.5 and PM10 levels were not dramatically changed with the lockdown policy. Besides the aerosol environment could facilitate the airborne transmission dynamics of the pandemic. For the second outbreak period from December 2020 to February 2021 without lockdown policy, PM2.5, PM10, CO and O3 showed low correlation with r values, 0.323, 0.321, 0.071 and 0.066, respectively. This is due to the increasing of traffic air pollutants and other confounding from urban activities and also the infection cases which came from many routes. However during both peak of COVID-phases Bangkok’s air quality had improved and the disease control policy continued to be practiced.
Keywords: COVID-19, Bangkok, Air pollutants, PM2.5, PM10