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Overseas wildfires linked to severe fine dust alert in Korea: study
The sky over central Seoul's Jongno District is clouded with fine dust, as the ultrafine dust concentration levels reached "bad" in most parts of the country, Nov. 24, 2025. Yonhap
By Lee Hae-rin
Overseas wildfires were among the causes of Korea’s heavy ultrafine dust episode on Nov. 24 last year, when advisories were issued in multiple central and western regions, according to the Seoul Institute of Health and Environment on Friday.
The institute said a detailed chemical analysis of fine dust that day showed smoke from biomass burning abroad had mixed with local emissions and long-range industrial pollution to worsen air quality.
Using a high-resolution aerosol mass spectrometer, the institute detected a clear fingerprint of biomass burning organic aerosol, or BBOA, in samples collected during the episode, confirming that overseas wildfires were one of several contributors.
An official said there were no major wildfires burning in Korea at the time, while large forest fires were reported in China with winds blowing toward the Korean Peninsula, making it likely that the smoke traveled from there.
Seoul’s ultrafine dust concentration that day averaged 76 micrograms per cubic meter, peaking at 92 micrograms per cubic meter. The advisory issued on Nov. 24 lasted for 11 hours and reached two distinct peaks, linked to a wildfire that broke out in Jilin province in northeastern China, the institute said.
Meanwhile, northern Association of Southeast Asian Nations countries and parts of Vietnam, Laos and Myanmar also experienced notable wildfire and crop-residue burning activity. The institute explained that a combination of regional fire activities and prevailing winds aligned with the BBOA signal identified in Seoul’s air that day.
On Nov. 24, ultrafine dust (PM2.5) advisories were issued in Seoul, where hourly levels briefly surged into the "very bad" range in the morning, as well as in neighboring Incheon, Gyeonggi Province and the Chungcheong region, including the administrative city of Sejong.
The sky over central Hwaseong Fortress in Suwon, Gyeonggi Province, is clouded with fine dust, as the ultrafine dust concentration levels reached "bad" in most parts of the city, Nov. 24, 2025. Yonhap
The institute said the episode was characteristic of Korea’s cold-season smog, in which local vehicle and heating emissions, transboundary industrial pollution and episodic contributions from biomass burning combine. However, the strong BBOA signal made the role of overseas fires more visible than in this particular November event.
The institute analyzes organic aerosols in Seoul’s air by grouping them into four categories: components generated during cooking, those originating from vehicle exhaust, those from biomass burning such as wildfires and those formed after long-range transport and subsequent oxidation in the atmosphere.
As Seoul is a densely populated city with a high concentration of restaurants, organic aerosols produced during cooking are considered one of the city’s major sources of local emissions.
"We are increasingly able to pinpoint the specific drivers behind high-concentration pollution episodes," Park Joo-sung, head of the Seoul Institute of Health and Environment, said, adding that the institute will "produce and share air quality data based on cutting-edge analytical equipment and contribute to managing the city’s air."