Smog returned to blanket most of greater Bangkok yesterday morning, which the Pollution Control Department attributed to stagnant air trapping vehicle emissions.
Out of the 58 air quality monitoring stations in the capital, 50 reported unsafe levels of ultra-fine dust measuring 2.5 micrometres or less in diameter, said PCD chief Pralong Damrongthai yesterday.
PM2.5 peaked at 81 microgrammes per cubic metre (μg/m³) over the previous 24 hours. The PCD's safe limit is set at 50μg/m³, or twice the international standard. Unsafe PM2.5 levels hit Bang Kapi, Bang Khunthian, Bang Na, Din Daeng, Pathumwan, Phaya Thai, Thon Buri, Wang Thonglang and Yannawa districts.