Seoul issued an ultrafine dust advisory on Saturday.
 
This is the third advisory the Seoul Metropolitan Government has announced since it introduced a fine dust forecast program in October. The first two were issued on December fourth and 20th, and the first dust watch came on December fifth.
 
An ultrafine dust advisory is issued when the average concentration of dust particles surpasses 60 micrograms per cubic meter for more than two hours. The advisory is lifted when the level of dust falls below 45 micrograms per cubic meter. 

A watch is issued when the concentration of dust particles exceeds 80 micrograms per cubic meter for more than two hours.
 
Seoul said the concentration of ultrafine dust reached 62 micrograms per cubic meter at 8 a.m. Saturday. The level rose to about 70 micrograms, which is three times higher than the usual concentration recorded during the daytime.
 
The National Institute of Environmental Research projected that not only the metropolitan area but also Chungcheong and Gangwon provinces will see two to four times higher level of the dust on Saturday.
 
The institute blamed the surge in fine dust levels to the smog coming in from China’s three northeastern provinces and a rise in air pollution at home. 

People in the affected areas are advised to stay indoors.