Pai district in Mae Hong Son province, one of the best known tourist destinations in the North, experienced the highest level of hazardous ultrafine dust in the country on Wednesday.
The highest level of PM2.5 -- 356 micrograms per cubic metre (µg/m3) -- was recorded in tambon Wiang Tai, according to a daily report of air quality data from the Pollution Control Department (PCD).
The PM2.5 levels nationwide ranged from 10 to 356 µg/m3 while the safe level is 50 µg/m3.
