Some 35 areas in Bangkok began experiencing an unhealthy level of hazardous PM2.5 pollution Sunday morning, prompting City Hall to step up measures to curb the ultra-fine dust particles in the air.
It also warned residents of how to avoid possible health impacts from the pollution.
The safe threshold of the PM2.5 dust is no more than 37.5 microgrammes per cubic metre (µg/m3), officials from AirBKK, the air quality information centre of the Bangkok Metropolitan Administration (BMA), said following the release of the figures.
The average PM2.5 dust levels measured across the city through its air quality measurement stations as of 7am Sunday ranged from 26.5 to 53.4 µg/m³, said the centre.
A number of areas in Nong Khaem, Thon Buri, Klong Sam Wa and Thawi Watthana logged 43.8 µg/m³ or higher, making them among the most air polluted zones in the city.
Dusit only slightly exceeded the safe level with 37.6 µg/m³, said the centre.
Other than these 35 zones where PM2.5 levels all exceeded the safe level, earning them orange status on the colour-coded air quality monitoring and warning system, the overall air quality in the other parts of Bangkok was considered moderate, said AirBKK.
The poor air quality was attributed mainly to stagnant air caused by poor air ventilation in the city, said the centre.
Responding to the poor air quality, the BMA's Department of Environment asked other agencies involved to begin implementing this season's operational plan for curbing dust levels.
Bangkok residents, especially people with underlying health conditions, were also advised to wear facemasks while outdoors, avoid intense outdoor physical exercise and pay extra attention to any unusual health symptoms such as coughing, shortness of breath and eye irritations. They should seek medical advice if the symptoms persist.