Air pollution shrouds Chiang Mai in northern Thailand on March 10, 2023. (Photo source: AFP)

Hanoi - Government agencies in Thailand's Chiang Mai were ordered to let staff work from home to protect their health as levels of PM2.5 smog surged to almost unprecedented levels.

Local residents have been requested to limit going outdoors amidst hazardous levels of air pollution.

On April 7 morning, the air monitoring website IQAir ranked Chiang Mai as the most polluted major city in the world, ahead of regular hotspots such as Delhi and Lahore of India.

Levels of the most dangerous PM2.5 particles - so tiny they can enter the bloodstream - were more than 66 times the World Health Organization's annual guideline, according to IQAir.

This tourist city has been shrouded in smoke from forest fires and seasonal agricultural burning in recent weeks.

According to the Thai Ministry of Health, nearly 2 million people in Thailand have been hospitalised for respiratory illnesses related to air pollution so far this year.

In February, the Thai government advised people to wear masks when going out and consider working from home to avoid PM2.5 fine dust pollution.