Toxic smog has blanketed Seoul, Daegu, Jeonju and other parts of the country since Saturday. The smog carries more heavy metal particles than the Mongolian sandstorms that plague the country in spring.
Analysis at a weather station in Bulgwang-dong, Seoul showed that the smog carried 5 to 11 times higher levels of arsenic and 8 to 26 times higher concentration of selenium than last year's sandstorms, the National Institute of Environmental Research said Tuesday.
The smog also contained 3 to 4 times more sulfur oxides and nitrogen oxides than the average smog measured in January last year and 2 to 3 times more arsenic and lead.
Up to 171 ㎍/㎥, 225 ㎍/㎥, and 183 ㎍/㎥ of ultrafine particles less than 2.5 µm in diameter were detected in Bulgwang-dong, Daejeon and Baeknyeong Island. Ultrafine particles can cause respiratory diseases because they reach the lungs directly without being filtered through the nose.
These figures are just a quarter to one-sixth of the 993 ㎍/㎥ of ultrafine particles found in heavy smog in Beijing on Saturday night, but still 3 to 4 times higher than the ambient air quality standard here.
The smog was blown in from China on a northwesterly wind due to large quantities of vapor as a result of melting snow, said Lee Sang-duk of the NIER said. "Patients with respiratory ailments should be especially careful and refrain from going outside," he added.
Almost all the smog is expected to disappear in strong winds on Wednesday, though it is likely to recur throughout the month, according to the Korea Meteorological Administration.