Han C, et al. J Korean Med Sci. 2018 Jun;33(30):e193. https://doi.org/10.3346/jkms.2018.33.e193

Both domestic emissions and transported pollutants from neighboring countries affect the ambient fine particulate matter (PM_2.5) concentration of Seoul, Korea. Diverse measures to control the coronavirus disease 2019 (COVID-19), such as social distancing and increased telecommuting in Korea and the stringent lockdown measures of China, may reduce domestic emissions and levels of transported pollutants, respectively. In addition, wearing a particulate-filtering respirator may have decreased the absolute PM_2.5 exposure level for individuals. Therefore, this study estimated the acute health benefits of PM_2.5 reduction and changes in public behavior during the COVID-19 crisis in Seoul, Korea. To calculate the mortality burden attributable to PM_2.5, we obtained residents’ registration data, mortality data, and air pollution monitoring data for Seoul from publicly available databases. Relative risks were derived from previous time-series studies. We used the attributable fraction to estimate the number of excessive deaths attributable to acute PM_2.5 exposure during January to April, yearly, from 2016 to 2020, and the number of mortalities avoided from PM_2.5 reduction and respirator use observed in 2020. The average PM_2.5 concentration from January to April in 2020 (25.6 μg/m³) was the lowest in the last 5 years. At least −4.1 μg/m³ (95% CI: −7.2, −0.9) change in ambient PM_2.5 in Seoul was observed in 2020 compared to the previous 4 years. Overall, 37.6 (95% CI: 32.6, 42.5) non-accidental; 7.0 (95% CI: 5.7, 8.4) cardiovascular; and 4.7 (95% CI: 3.4, 6.1) respiratory mortalities were avoided due to PM_2.5 reduction in 2020. By considering the effects of particulate respirator, decreases of 102.5 (95% CI: 89.0, 115.9) non-accidental; 19.1 (95% CI: 15.6, 22.9) cardiovascular; and 12.9 (95% CI: 9.2, 16.5) respiratory mortalities were estimated. We estimated that 37 lives were saved due to the PM_2.5 reduction related to COVID-19 in Seoul, Korea. The health benefit may be greater due to the popular use of particulate-filtering respirators during the COVID-19 crisis. Future studies with daily mortality data are needed to verify our study estimates.

Background: Although the ongoing epidemics of Coronavirus disease 2019 (COVID-19) may have affected the mortality trend of the nation, the national level assessment of excess mortality (changes in overall mortality in the entire population) is still scarce in Korea. Therefore, this study evaluated the excess mortality during the COVID-19 pandemic in Korea using the certified mortality data. Methods: Monthly mortality and population data from January 2013 to June 2022 was obtained from the National Health Insurance Service database and Statistics Korea. A quasi-Poisson interrupted time-series model adjusted for age structure, population, seasonality, and long-term trends was used to estimate the counterfactual projections (expected) of mortality during the COVID-19 pandemic (March 2020 to June 2022). The absolute difference (observed—expected) and ratio (observed / expected) of mortality were calculated. Stratified analysis based on pandemic years (years 2020, 2021, and 2022), sex, and age groups (aged 0–4, 5–19, 20–64, and ≥ 65 years) were conducted. Results: An 8.7% increase in mortality was observed during the COVID-19 pandemic [absolute difference: 61,277 persons; ratio (95% confidence interval (CI)): 1.087 (1.066, 1.107)]. The gap between observed and estimated mortality became wider with continuation of the pandemic [ratio (95% CI), year 2020: 1.021 (1.003, 1.040); year 2021: 1.060 (1.039, 1.080), year 2022: 1.244 (1.219, 1.270)]. Although excess mortality across sex was similar, the adult [aged 20–64, ratio (95% CI): 1.059 (1.043, 1.076)] and elderly [aged 65-, ratio (95% CI): 1.098 (1.062, 1.135)] population showed increased excess mortality during the pandemic. Conclusions: Despite Korea's successful quarantine policy response, the continued epidemic has led to an excess mortality. The estimated mortality exceeded the number of deaths from COVID-19 infection. Excess mortality should be monitored to estimate the overall impact of the pandemic on a nation.

Although several studies have evaluated the association between fine particulate matter (PM_2.5) and acute lower respiratory infection (ALRI) in children, their results were inconsistent Therefore, we aimed to evaluate the association between short-term exposure to PM_2.5 and ALRI hospitalizations in children (0–5 years) living in seven metropolitan cities of Korea. The ALRI hospitalization data of children living in seven metropolitan cities of Korea from 2008 to 2016 was acquired from a customized database constructed based on National Health Insurance data. The time-series data in a generalized additive model were used to evaluate the relationship between ALRI hospitalization and 7-day moving average PM_2.5 exposure after adjusting for apparent temperature, day of the week, and time trends. We performed a meta-analysis using a two-stage design method. The estimates for each city were pooled to generate an average estimate of the associations. The average PM_2.5 concentration in 7 metropolitan cities was 29.0 μg/m³ and a total of 713,588 ALRI hospitalizations were observed during the 9-year study period. A strong linear association was observed between PM_2.5 and ALRI hospitalization. A 10 μg/m³ increase in the 7-day moving average of PM_2.5 was associated with a 1.20% (95% CI: 0.71, 1.71) increase in ALRI hospitalization. While we found similar estimates in a stratified analysis by sex, we observed stronger estimates of the association in the warm season (1.71%, 95% CI: 0.94, 2.48) compared to the cold season (0.31%, 95% CI: −0.51, 1.13). In the two-pollutant models, the PM_2.5 effect adjusted by SO₂ was attenuated more than in the single pollutant model. Our results suggest a positive association between PM_2.5 exposure and ALRI hospitalizations in Korean children, particularly in the warm season. The children need to refrain from going out on days when PM_2.5 is high.

Background: Unlike other countries, South Korea did not implement a large-scale lockdown or closure of businesses to manage the coronavirus disease 2019 (COVID-19) pandemic, but relied on changes in population behaviours and early isolation and treatment of patients. It is important to evaluate the effectiveness of such alternative strategies on the mortality of the general population. Methods: Mortality and monthly population data from 2013 to 2020 were obtained. A quasi-Poisson regression model adjusting for age structure, seasonality and time was used to evaluate whether underlying trends for monthly mortality rate have changed with the pandemic. Stratification analyses based on sex and location of deaths (inside vs outside of medical facilities) were conducted. Results: The risk estimates showed no changes in non-accidental mortality during the COVID-19 pandemic [relative risk (RR) (95% confidence interval, 95% CI), slope change: 1.00 (1.00, 1.01), step change: 0.99 (0.97, 1.01)] compared with those before the pandemic. In cause-specific analysis, there was an abrupt and sustained decrease in the mortality rate of respiratory diseases [RR (95% CI), step change: 0.81 (0.77, 0.84)]. In the analysis of deaths by location, an increase in non-accidental mortality [RR (95% CI), slope change: 1.01 (1.01, 1.02), step change: 1.16 (1.11, 1.22)] and several cause-specific mortalities was observed outside of medical facilities. Conclusions: The non-accidental mortality rate in South Korea for the first year of the pandemic followed the historical trends. However, there was a decrease in mortality associated with respiratory diseases, and an increase in mortality occurring outside of medical facilities. The findings may be attributed to changes in public behaviours, and availability of medical resources during the pandemic.