The air quality in Chiang Mai is expected to improve slightly this weekend as winds will pick up speed, according to the province's command centre for PM2.5 pollution prevention.
Assoc Prof Chakrit Chot-amornsak, a member of the centre to combat wildfire and ultrafine dust particles at Chiang Mai University, gave his forecast on the province's air quality yesterday.
However, the dust pollution levels in certain areas will remain "unhealthy for sensitive groups" or "unhealthy" for the general public due to weak winds, he said, adding that some rainfall is also expected.
Assoc Prof Chakrit said wind speeds will increase over the weekend and slightly improve the air quality with most areas expected to see dust pollution at a "moderate" level.
He said the air quality in some areas is likely to return to a satisfactory level with air pollution posing little or no risk.
Readings for PM2.5 pollution in most areas yesterday morning were "unhealthy for sensitive groups".
People with poor health are advised to wear face masks when going outside and avoid going outdoors for extended periods.
Outdoor activities should be avoided if PM2.5 readings exceed 51 microgrammes per cubic metre.
The so-called "safe" threshold of the Pollution Control Department is 50µg/m³.
Chiang Mai has been ranked among the planet's three worst cities for pollution since the start of March.
Chiang Mai ranked as the third most air-polluted city in the world on March 3, with an average PM2.5 dust level higher than 200.
Local authorities revealed that the situation had caused 30,000 people to seek hospital treatment because of respiratory illnesses over the past three months.
A total of 31,788 patients suffered from air pollution-related illnesses from January to March 5, said Dr Suwanchai Wattanayingcharoen, director-general of the national health department.