Unsafe smog levels have blanketed Bangkok, with the worst levels in Phra Nakhon district, and 23 other provinces also plagued with air pollution.
The Pollution Control Department reported that levels of particulate matter 2.5 micrometres and less in diameter (PM2.5) ranged from 55 to 89 microgrammes per cubic metre of air in the capital over the past 24 hours to 9am on Tuesday. The government-set safe threshold is 50mcg.
Unsafe PM2.5 levels were detected in 50 of 52 areas in greater Bangkok. Only Bang Sao Thong district of Samut Prakan, with PM2.5 at 48mcg, and Muang district of Samut Sakhon, 50mcg, were deemed healthy.
In general the air pollution was worse than on Monday, the department said.
Elsewhere, unsafe smog levels were reported in some districts of Ayutthaya, Chachoengsao, Chiang Mai, Chiang Rai, Chon Buri, Kanchanaburi, Lampang, Nakhon Pathom, Nakhon Ratchasima, Nakhon Sawan, Nan, Nonthaburi, Pathum Thani, Phayao, Phrae, Prachin Buri, Ratchaburi, Rayong, Samut Prakan, Sa Kaeo, Saraburi, Suphan Buri and Tak provinces.
The worst PM2.5 level nationwide, 94mcg, was reported in tambon Na Phra Lan of Chalerm Prakiat district in Saraburi, where there are busy rock quarries.