Air pollution in Bangkok on Monday returned to hazardous levels in 19 areas.
Pollution Control Department (PCD) air monitoring stations showed levels of PM2.5 -- toxic ultrafine particulate matter -- exceeded the so-called safe threshold of 50 microgrammes per cubic metre (µg/m³) in parts of the city.
Air quality across the city ranged between 41-67 µg/m³.
The PCD warned of more air pollution to come as stagnant air cold-season conditions prevent airborne particulate matter from dispersing.