The share of domestic factors in Seoul’s ultrafine dust particles has increased over the past five years, while the ratio of China’s contribution to the local particulate pollution has been stagnant, a report showed Saturday.

According to the report issued by the Seoul Metropolitan Government, homegrown pollutants were responsible for 26 percent of the capital’s ultrafine particles smaller than 2.5 micrometers in diameter, or PM 2.5, as of 2019, marking a rise from 22 percent in 2016.

In contrast, the ratio of China’s contribution to Seoul’s PM 2.5 concentrations remained unchanged at 38 percent in the 2016-19 period, the report noted.

North Korea and other foreign regions were to blame for only 4 percent of the city’s PM 2.5 pollution in 2019, down sharply from 17 percent in 2016.

The report said the PM 2.5 self-contribution ratio for other parts of South Korea, excluding Seoul, jumped from 23 percent to 32 percent. (Yonhap)