key: cord-0943526-eydvw7aa
authors: Park, Hyung Kyu; Shim, Jung Yeon
title: Changes in air pollution and childhood respiratory viral infections in Korea post-COVID-19 outbreak
date: 2022-02-17
journal: Clin Exp Pediatr
DOI: 10.3345/cep.2021.01585
sha: b8bf6e19859b927a69cdf71e8cffa61536e80329
doc_id: 943526
cord_uid: eydvw7aa

nan

Control and Prevention Agency were collected from February to May annually in 2015-2021. 7 We observed decreasing trends in ambient NO2, PM2.5, PM10, and SO2 levels in 2020 since the beginning of the pandemic and following lockdowns compared to the same periods before the pandemic (Fig. 1 ). Since industrial emissions and traffic contribute largely to these air pollutants, noticeable decreases were observed after the implementation of the lockdowns. However, the levels of CO and O3 did not show significant changes compared to those in previous years. A marked reduction of ambient NO2 and paradoxical increase of ambient O3 levels at urban stations during the pandemic were also observed abroad, such as in Brazil, China, and Europe. 8) Increased O3 levels during lockdowns may be attributed to a reduction in NOx emissions, which leads to lower O3 titration, since its formation depends on the ratio of nonmethane hydrocarbons, nitrogen oxides, and volatile organic compounds in the atmosphere. 8) In 2021, when social distancing between individuals persisted while most industries in South Korea and nearby countries such as China and India resumed, several parameters including PM2.5, PM10, SO2, and O3 exhibited slight increases compared to those in 2020 (Fig. 1) . A steep increase in ambient PM10 seems to have resulted from several sandstorms that began and spread from the Eastern Gobi desert steppe during March 2021. 9) Respiratory viral infections in the childhood population showed a dramatic decrease after the COVID-19 outbreak since public health measures were implemented (Fig. 2) . The average number of respiratory virus detections from February to May each year before the pandemic was 23,120, but in 2020 and 2021, only 5,563 and 4,298 cases were detected, showing reductions of 75.9% and 81.4%, respectively. Several studies from abroad also demonstrated decreased trends in respiratory viruses and hospital use. A reduction in pediatric asthma encounters and decreased steroid prescriptions were observed, probably due to decreased rhinovirus infections during the pandemic. 3) In addition, the global decline in influenza virus circulation was concurrent with the pandemic, and most other respiratory viruses exhibited de-could not analyze the effect of air pollution on respiratory viral infections, as mandatory mask wearing and social distancing may have been confounding variables. In addition, we could not gather regional information on viral data from the website.

In conclusion, nationwide social distancing and public health measures implemented by the South Korean government since the COVID-19 outbreak resulted in both improved ambient air pollution levels and decreased respiratory viral infection rates. Further studies of the relationship between air pollution and viral transmission are needed to establish a national policy to improve the health status of the childhood population and improve air quality.

creased trends in 2020 as well. 2, 3, 10) However, in early 2021 in South Korea, a slight increase in rhinovirus and bocavirus infection was observed, and adenovirus was detected in small numbers. Similar patterns of increasing rhinovirus and adenovirus detection in early 2021 were also found abroad. 10) The exact causes of different patterns of viral circulation after COVID-19 remain unclear. In addition to relaxed COVID-19 health measures and the expansion of offline schools, viral factors such as types of transmission mechanism or survival time on the surface due to structural differences may contribute to different circulating patterns. 10) This study has a few limitations. First, we were unable to estimate the prevalence of respiratory viral infections among hospitalized patients because of the lack of total sample numbers. Second, we 

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