Chiang Mai was ranked as the third most air-polluted city in the world on Wednesday, with an average PM2.5 dust level higher than 200.
The northern province is battling with a critical level of air pollution due to wildfire smoke, with the average amount of PM2.5 exceeding the safe level at all four air quality monitoring stations in the municipal area on Wednesday.
An air quality monitoring station in tambon Suthep of Muang district reported PM2.5 of 102 µg/m3 -- the highest amount of all four stations.
On the website of AirVisual, Chiang Mai was ranked the third most polluted in the world as of 11am on Wednesday, after Lahor in Pakistan and New Delhi in India.
Some 928 hotspots were detected across 17 northern provinces on Wednesday morning, according to deputy commander of the 3rd Army Region Maj Gen Thanadpol Kosaisewee, who is the deputy chief of a command tackling air pollution problems in the region.
In Tak, PM2.5 and PM10 exceeded the safe level for four consecutive days, affecting people's health and road visibility.
On Wednesday, PM2.5 and PM10 in the province were measured at 114 and 171 µg/m3 -- above health-hazard levels -- in Mae Sot district. People were told to avoid all outdoor activities and stay away from areas with high air pollution.
Tak governor Pongrat Piromrat said the province had laid out measures to prevent forest fires and prohibit burning for two months starting from March 1. Those who burned in forests or were found to carry hunting equipment would be charged by forest patrol officers, the governor warned.
Director-General of the Department of Health Suwanchai Wattanayingcharoen said the tropical storms from March 1-4 in the upper part of the country would help reduce PM2.5 in Bangkok and its vicinity, the Central Plains, the East and the lower North from March 5-7.
However, some areas in the North, the Central Plains and the Northeast might experience more air pollution due to outdoor burning in the country and smoke from neighbouring countries, he said.
The doctor advised people to protect themselves by wearing a face mask every time they venture outside and keep abreast of the air pollution situation on the official website and application of the Department of Pollution Control.