Atmosphere particulate matter and respiratory diseases during COVID-19 in Korea.

We aimed to examine the impact of COVID-19 non-pharmaceutical interventions (NPIs) on the relationship between air pollutants and hospital admissions for respiratory and non-respiratory diseases in six metropolitan cities in South Korea. This study compared the associations between particulate matter (PM and PM) and hospital admission for respiratory and non-respiratory diseases before (2016-2019) and during (2020) the implementation of COVID-19 NPIs by using distributed lag non-linear models. In the Pre-COVID-19 period, the association between PM and admission risk for asthma and COPD showed an inverted U-shaped pattern. For PM, S-shaped and inverted U-shaped changes were observed in asthma and COPD, respectively. Extremely high and low levels of PM and extremely low levels of PM significantly decreased the risk of admission for asthma and COPD. In the Post-COVID-19 outbreak period, the overall cumulative relationship between PM and PM and respiratory diseases and the effects of extreme levels of PM and PM on respiratory diseases were completely changed. For non-respiratory diseases, PM and PM were statistically insignificant for admission risk during both periods. Our study may provide evidence that implementing NPIs and reducing PM and PM exposure during the COVID-19 pandemic has contributed to reducing hospital admissions for environment-based respiratory diseases.