South Korea has experienced more days of ultrafine dust blanketing the country so far this year compared to the past two years, government data showed.

According to the Ministry of Environment, the concentration level of ultrafine dust particles -- about 1/30 the thickness of a strand of human hair -- from January to March this year marked the worst level at 32 micrograms per cubic meter, up 2 micrograms per cubic meter from the same period in 2015 and 2016. That level is equal to an AQI of 93 on the US Environment Protection Agency’s scale.

Seoul saw the problem worsen sharply compared to the past two years, reporting a total of 14 “bad” dust days in the three-month period this year. The capital had only two days of bad levels of airborne dust concentration last year and five the year before.

The cutoff used – 80 micrograms per cubic meter -- is much less strict than the 25 microgram limit put forward by the World Health Organization.

Nationwide, the number of bad dust days stood at eight this year, unchanged from 2015 but double that of 2016.