Unsafe levels of smog were measured in 43 out of 50 areas in greater Bangkok on Friday morning, with the worst pollution in Samut Sakhon province, the Pollution Control Department reported.
Over the 24 hours to 9 am, the levels of particulate matter 2.5 micrometres and less in diameter ranged from 52 to 113 microgrammes per cubic metre of air.
The safe threshold is set at 50mcg by the government.
The worst pollution was recorded in tambon Mahachai of Muang district in Samut Sakhon province.
Other highly unsafe areas were in Bang Kapi, Bang Khunthian, Bang Na, Din Daeng, Pathumwan, Phaya Thai, Thon Buri, Wang Thong Lang and Yannawa districts of Bangkok.
Similar levels were recorded in Muang district of Nakhon Pathom; Bang Kruai and Pakkret districts of Nonthaburi; Khlong Luang district of Pathum Thani; Bang Sao Thong, Muang and Phra Pradaeng districts of Samut Prakan; and Krathum Baen district of Samut Sakhon.
PM2.5 levels in greater Bangkok on the previous day ranged from 47 to 81mcg
