A comprehensive examination of temporal-seasonal variations of PM and PM in taiwan before and during the COVID-19 lockdown.

COVID-19 has been a significant global concern due to its contagious nature. In May 2021, Taiwan experienced a severe outbreak, leading the government to enforce strict Pandemic Alert Level 3 restrictions in order to curtail its spread. Although previous studies in Taiwan have examined the effects of these measures on air quality, further research is required to compare different time periods and assess the health implications of reducing particulate matter during the Level 3 lockdown. Herein, we analyzed the mass concentrations, chemical compositions, seasonal variations, sources, and potential health risks of PM and PM in Central Taiwan before and during the Level 3 lockdown. As a result, coal-fired boilers (47%) and traffic emissions (53%) were identified as the predominant sources of polycyclic aromatic hydrocarbons (PAHs) in PM, while in PM, the dominant sources of PAHs were coal-fired boilers (28%), traffic emissions (50%), and iron and steel sinter plants (22.1%). Before the pandemic, a greater value of 20.9 ± 6.92 μg/m was observed for PM, which decreased to 15.3 ± 2.51 μg/m during the pandemic due to a reduction in industrial and anthropogenic emissions. Additionally, prior to the pandemic, PM had a contribution rate of 79% to PM, which changed to 89% during the pandemic. Similarly, BaPeq values in PM exhibited a comparable trend, with PM contributing 86% and 65% respectively. In both periods, the OC/EC ratios for PM and PM were above 2, due to secondary organic compounds. The incremental lifetime cancer risk (ILCR) of PAHs in PM decreased by 4.03 × 10 during the pandemic, with PM contributing 73% due to reduced anthropogenic activities.