Buildings are shrouded in smog in Seoul, South Korea, Nov. 16, 2020. Thick haze engulfed South Korea's capital city Seoul as well as its surrounding areas on Monday. (Xinhua/Wang Jingqiang)

A train crosses a bridge over the Hangang River shrouded in smog in Seoul, South Korea, Nov. 16, 2020. Thick haze engulfed South Korea's capital city Seoul as well as its surrounding areas on Monday. (Xinhua/Wang Jingqiang)

Buildings are shrouded in smog in Seoul, South Korea, Nov. 16, 2020. Thick haze engulfed South Korea's capital city Seoul as well as its surrounding areas on Monday. (Xinhua/Wang Jingqiang)

Buildings are shrouded in smog in Seoul, South Korea, Nov. 16, 2020. Thick haze engulfed South Korea's capital city Seoul as well as its surrounding areas on Monday. (Xinhua/Wang Jingqiang)