Seoul’s air pollution Tuesday recorded the second most serious figure among major metropolitan areas worldwide, recent data showed.

According to air quality monitoring website AirVisual, the air quality index of Seoul recorded 179 as of 7 a.m. The worst was New Delhi, at 187.

The main cause of the pollution is the inflow of fine dust particles from outside of Korea, including those from eastern portions of China.

“Fine dust from outside the country flowed in as the west wind blew when stationary high pressure was remaining in the sky,” said a National Institute of Environmental Research official. “The air condition of the entire capital area including Seoul was severe as the atmosphere stagnated.”

On the same day, Incheon, some 27 kilometers southwest of Seoul, showed a serious air condition rating of 139. The city ranked eighth in AQI.

AQI is an index that gathers the amount of pollutants in the air and displays air pollution rates around the world in real time, offering a scale from zero to 300. An AQI over 100 indicates an elevated level of pollution.

By Byun Hee-jin (hjbandi9@heraldcorp.com)