The Bangkok Metropolitan Administration (BMA) has warned that PM2.5 air pollution will shroud the capital for almost a week over the festive period.
BMA spokesman Pol Capt Pongsakorn Kwanmuang told media that City Hall has prepared measures to combat the return of the hazardous small dust particles, levels of which are predicted to peak between this Thursday, Christmas Eve, and next Tuesday.
The spike in PM2.5 is caused by climate patterns, particularly the current lack of air circulation to disperse the particles, he said.
The Pollution Control Department has set the country's maximum "safe" level of PM2.5 at 50 microgrammes per cubic metre (µg/m³), which is double the World Health Organization's recommendation.
To keep PM2.5 readings under that mark, the BMA has shrugged off legal threats from haulage firms and once again promised to ban lorries with six wheels or more from entering inner Bangkok between 6am and 9pm.
Once levels exceed 50 µg/m³ in the majority of areas, it will close schools for three weekdays and arrest anyone found to be polluting, he said.