Continuing forest fires pushed air quality in northern Mae Hong Son province well beyond the safe level on Monday.
EDAfter 10 days during which particulate matter smaller than 10 micrometres (PM10) were found to be within the safety limit of 120 micrograms per cubic metre – a respite credited to recent rains – the level rose again on Sunday to 150 micrograms.
On Monday, the level at 5am was 164 micrograms, and by 10am 177 micrograms.
More forest fires were reported along the Myanmar border in the past three days, contributing to the rise in PM10, said a source at a military unit based west of Muang Mae Hong Son.
Soldiers joined volunteers in extinguishing the blazes.
Khun Yuam district chief Narongchai Jindapan said residents were setting fires to clear brush so they could return later and forage for mushrooms and edible buds, which are believed to become more plentiful when rainfall accompanies intense heat, such as from fires or very hot weather.
At 10am on Monday the Pollution Control Department reported unhealthy PM10 levels in Mae Hong Son (177 micrograms), Muang Chiang Mai (124) and Chiang Rai’s Muang district (137) and Mae Sai district (123).