In Lampang’s Mae Moh district, the amount of PM10 hovered around 129 micrograms per cubic metre of air. In Mae Hong Son’s Muang district, the PM10 amount was at 125 micrograms.

Safety standards specify 120 micrograms or less.

While the department did not find serious air pollution in other northern provinces, its director-general Jatuporn Buruspat admitted that spraying water in Chiang Mai province had affected air monitoring in the area.

“We have already raised the issue with the Interior Ministry. We are told staff are now barred from spraying water near air-quality monitoring stations,” Jatuporn said.

Various authorities have sprayed water as a means to fight smog but if air-quality monitoring stations are affected by the water, the information gathered may not reflect actual situation.