Many parts of Bangkok have been blanketed in PM2.5 haze this week due to poor air circulation and an increase in hotspots in the provinces and neighbouring countries, said Bangkok governor Chadchart Sittipunt.
The poor air quality was reported not only in the capital but also in the central and northeastern provinces, and the dust pollution stemmed from stagnant air, burning of crops and weeds, and the wind blowing from the east, he said.
However, he said the situation did not yet warrant a ban on trucks entering Bangkok. City Hall will implement that measure if the levels of ultra-fine micropollutants in five districts stay in the "red" zone for two days straight.
Over the past 24 hours, PM2.5 levels in Bangkok have ranged from 48.2 to 95.1 microgrammes per cubic metre. Six areas hit the "red" level, with Nong Khaem district recording the highest reading at 95.1 µg/m³.
According to the governor, the ultra-fine dust levels in Nong Khaem district reached the red level (exceeding 75.1 µg/m³), and City Hall will inspect the On Nut waste incineration plant and determine if the facility might be a contributing factor.
Air circulation during Jan 9-17 is forecast to be poor, meaning dust levels are likely to rise over the next few days before easing off.
Mr Chadchart also urged drivers to check their vehicles to help cut down emissions. So far, only 160,000 vehicles have been inspected -- far below the 500,000 target.
People are advised to limit outdoor activities and wear masks when going outside and vulnerable groups should watch for symptoms and visit the special respiratory clinics run by City Hall if needed, he said.
Mr Chadchart said the conditions are expected to improve over the weekend, and by Monday, dust pollution levels might have dropped to the "yellow" or "green" range.
Meanwhile, a fire in a forest reserve in Nakhon Ratchasima's Pak Chong district has continued for three days and efforts to contain the blaze were being ramped up to prevent it from spreading to nearby residential areas.
Teams from five agencies were mobilised to fight the fire on Wednesday night, but it remained out of control as of yesterday morning.
This is the fourth forest fire since the start of the year, with over 1,000 rai of land already damaged.