The Ministry’s Department of Health said there were health risks associated with exposing children to a high level of small particulate matter of up to 10 microns in diameter (PM10).

Chiang Mai, Chiang Rai, Nan and Mae Hong Son provinces have implemented a 60-day ban of outdoor burning and forest fires until mid-April.

The current dry period, which coincides with the school break, has resulted in many provinces in the North recording PM10 readings due to outdoor burning and forest fires.

The most vulnerable are the elderly, pregnant women, people with chronic respiratory or heart diseases and young children, according to the department’s deputy chief Dr Danai Theewanda.

Young children’s lungs are not fully developed and in general they breathe more frequently than adults while their immunity is not as strong as adults generally, the doctor said.

He said if children had to go outside during a haze period they should wear a face mask.

“Parents should also keep an eye out for usual haze-induced symptoms like skin or eye irritation, coughing, abnormal breathing, nausea or vomiting and take children to see doctor [if they are symptomatic],” he added.