The air quality in the Seoul metropolitan area is bad...Overnight, smog flows from China.

While the concentration of ultrafine dust in the metropolitan area, including Seoul, has been "bad" all day, smog from China is also expected to flow in overnight.

According to the National Institute of Environmental Research, the concentration of ultrafine dust in the Midwest, including the metropolitan area, is expected to remain "bad" until tomorrow (21st) due to the stagnant atmosphere overnight and the inflow of smog from China.

However, he added that the concentration of ultrafine dust will not rise to a "very bad" level because the amount of smog introduced is not large.

The concentration of ultrafine dust is classified into 'bad' if it exceeds 36μg (microgram) per cubic meter, and 'very bad' if it exceeds 76μg.