Toxic smog prompts Bangkok to shut schools for a week

Choking air pollution has forced authorities to shut nearly 450 schools on Wednesday in the Thai capital for the rest of the week and people celebrating next week's Lunar New Year holiday were urged to curb the use of incense and fireworks.

The Thai capital has been shrouded in murky haze for weeks, forcing residents to don masks and sparking social media criticism of the uneven response by the government.

Air quality in Bangkok is hovering at unhealthy levels as the number of hazardous dust particles known as PM 2.5 exceeded the safe level in 41 areas around the capital, according to the Department of Pollution Control.

PM 2.5 is a mixture of liquid droplets and solid particles that can include dust, soot, and smoke, one of the main measures of the Air Quality Index (AQI).

AQI reported on Wednesday was 175 at midday, according to airvisual.com, which measures levels in cities worldwide, making Bangkok the fifth most polluted city. India's capital, New Delhi, ranked first at 257.

Reasons given for the lingering pall include exhaust from traffic, unfettered construction, the burning of crop stubble, and pollution from factories getting trapped in the city.

Authorities have seeded clouds to provoke rain, sprayed overpasses with water to catch micro-pollutants and even asked people not to burn incense sticks and paper during Chinese new year celebrations.

The measures so far have provoked derision from many Bangkok residents, while stocks of pollution masks have run out in many shops.

But on Wednesday the Bangkok Metropolitan Administration stepped up its health warnings, ordering all 437 city-controlled public schools to close from lunchtime until Friday while designating 1,500 square kilometres (580 square miles) of the city a “control area”.

“The situation will be bad until February 3 to 4, so I decided to close schools,” said Bangkok governor Aswin Kwanmuang, adding he hoped the move would also empty the road of cars on the school run.

Three to four of the city’s districts were “severely hit with smog”, he added.

The measurements are higher than some cities in China but well below the Indian capital New Delhi.