
Ultrafine dust levels were in the red (hazardous-to-health) in 46 out of the 77 provinces and in Greater Bangkok on Wednesday morning, with only 10 provinces reporting moderate to good air quality.
The Geo-Informatics and Space Technology Development Agency (Gistda) reported at 8am that particulate matter 2.5 micrometres and less in diameter (PM2.5) was at red levels in 46 provinces and at orange (starting to affect health) levels in 21 provinces. Most were in the Central Plain, the Northeast and the East.
The highest level of PM2.5 recorded over the preceding 24 hours was 151.1 microgrammes per cubic metre of air in Samut Sakhon province, followed by 125.1µg/m³ in Samut Songkhram, 121.1 in Saraburi, 115.7 in Phetchaburi, 111.7 in Lop Buri, 110.1 in Ratchaburi, 108 in Pathum Thani, 106.5 in Nakhon Pathom, 106.4 in Ayutthaya, 106.2 in Kalasin, 105.5 in Rayong, 104.9 in Maha Sarakham, 102.4 in Sa Kaeo, 102.3 in Ang Thong, 101.6 in Samut Prakan, 100.1 in Sing Buri and Chon Buri and 100 in Bangkok.
The government-set safe threshold is 37.5µg/m³.
Twenty-eight other provinces were at two-digit red levels of PM2.5, ranging from 76.6 to 98.3µg/m³.
In descending order, they were Nonthaburi, Chai Nat, Si Sa Ket, Khon Kaen, Nakhon Ratchasima, Chachoengsao, Suphan Buri, Roi Et, Surin, Buri Ram, Kanchanaburi, Nong Khai, Uthai Thani, Nakhon Pathom, Phetchabun, Ubon Ratchathani, Nakhon Sawan, Sukhothai, Kamphaeng Phet, Phitsanulok, Prachin Buri, Chaiyaphum, Prachuap Khiri Khan, Loei, Chanthaburi, Udon Thani, Yasothon and Sakon Nakhon.
Safe levels of PM2.5 were recorded in 10 northern and southern provinces.
Eight of them had moderate air quality with yellow levels of PM2.5 ranging from 26 to 36.4µg/m³.
In descending order, they were Lamphun, Phangnga, Ranong, Surat Thani, Chumphon, Nakhon Si Thammarat, Krabi and Chiang Rai.
Two provinces had good air quality (green levels of PM2.5) namely Chiang Mai (20.1µg/m³) and Mae Hong Son (16.1).
Twenty-one other provinces were shrouded with orange levels of PM2.5 ranging from 38 to 74.8µg/m³.
As of 10am on Wednesday, 103 schools in Bangkok had suspended onsite classes and switched to online learning due to the PM2.5 pollution crisis, which is forecast to last until Friday, said Bangkok governor Chadchart Sittipunt.
All 50 districts of Bangkok on Wednesday had a serious air quality problem, with five of them in a critical situation, according to the information published by AirBKK, City Hall’s air quality monitoring agency.
The governor blamed the situation on poor air ventilation in the capital which was coupled with high traffic emissions resulting from a number of factors, including more congestion on inner Bangkok’s roads where flyovers are now closed as part of the construction of the Orange Line electric train.
And in an effort to prevent polluting trucks from entering inner Bangkok at the moment, the Bangkok Metropolitan Administration (BMA) is on Thursday to begin banning trucks which have not registered for permission to enter Bangkok’s low-emission zones.
A total of 259 security cameras equipped with AI technology are to be used to detect trucks flouting the ban and tracing them to construction sites that may also face legal action for causing pollution, according to Mr Chadchart.
In the past trial using these cameras, it was found that about 2,500 such trucks had entered inner Bangkok each day, while only about 400 of them had registered to enter areas designated as low-emission zones, he said.
Violating the ban will lead to a maximum fine of 2,000 baht and/or a maximum of one month’s imprisonment, he said.
The BMA is also trying to contain biomass burning in Bangkok areas which has also exacerbated the air pollution situation, said the governor.
The BMA’s work-from-home campaign will also be extended up until Friday (Jan 24) as the air quality is expected to begin improve on Saturday, he said.

This Gistda map shows levels of PM2.5 in different colours in Thailand at 8am on Wednesday.