Ultrafine dust in Seoul soared to a record high level on Monday. 

According to the National Institute of Environmental Research, the average level of ultrafine dust in the capital through 3 p.m. was 118 micrograms per cubic meter, and was not expected to significantly drop for the rest of the day. 

That tops the previous worst day for Seoul. March 25th of last year saw the average level of ultrafine particles spike to 99 micrograms per cubic meter. Ultrafine dust monitoring began in 2015. 

An official of the institute attributed the uptick in fine dust levels to a mixture of local factors and factors from China. 

Gyeonggi Province also saw the ultrafine dust level hike to 114 micrograms per cubic meter during the day; many other cities and provinces also recorded high levels of ultrafine dust at 58 micrograms per cubic meter or higher. 

It prompted a total of ten cities and provinces to implement emergency measures to mitigate dust emissions, including the Seoul metropolitan area. 

Ultrafine dust, called PM-two-point-five, measures two-point-five micrometers or less in diameter, and is classified by the World Health Organization as a first-degree carcinogen.