The annual average concentration of ultrafine dust in South Korea last year was the lowest since observations began in 2015.

According to the environment ministry on Tuesday, South Korea saw an annual average concentration of 15-point-six micrograms of ultrafine dust per cubic meter, a 38-point-one percent decrease from 2015 and a 14-point-three percent decrease from 2023.

The number of days with “good” air quality, where the average daily concentration of ultrafine dust particles was 15 micrograms per cubic meter or less, reached a record high of 212.

The number of days with “bad” air quality, where the average stood at 36 micrograms per cubic meter or higher, was only 10, the lowest since records began.

The environment ministry said it was a combination of domestic policies, reduced foreign inflow of ultrafine dust, and favorable weather conditions that caused the air quality to improve.