Toxic air forces Thai officials to close Bangkok schools for rest of week

Bangkok's air quality has fallen to harmful levels with the quantity of unsafe dust particles -- known as PM2.5 -- exceeding what is considered safe in 41 areas around the capital, the country's Department of Pollution Control said in a Facebook post.

PM2.5 are microscopic particles smaller than 2.5 micrometers in diameter that are considered particularly harmful because they are small enough to lodge deep into the lungs and pass into other organs.

The Air Quality Index, AQI, is used by cities to determine levels of air pollution; according to the World Health Organization, AQI levels under 25 are considered to be acceptable for humans to breathe regularly. The AQI levels on Wednesday evening in Bangkok measured 175.

Boonrak Yodpetch, secretary general to the Office of Basic Education Commission, said the order for closures came from Prime Minister Prayut Chan-o-cha.

"[The Prime Minister] has ordered the Ministry of Education to consider closing the schools in order to mitigate the health effect," Yodpetch said Wednesday.

"[The] first action is to close down all schools in Bangkok and some schools in four to five provinces (near to Bangkok)," the official continued.

He said the order would continue through Friday and that a direct result would be the reduction of vehicle traffic. All students were allowed to remain at home except for students preparing for upcoming national tests. In those instances, individual schools could decide whether to reopen.

Related: Fine dust and toxic smog are suffocating these Asian countries

Yodpetch added that the situation will be reassessed again on Sunday to determine if schools would stay closed next week.

The order only affects city-managed public schools; private international schools operating in the capital are not compelled to close.

But at least three, the Rasami British International School, the Harrow International School Bangkok and Bangkok Patana School, opted to follow suit and have also closed for the next two days.

Earlier Wednesday, Asawin Kwanmuang, the governor of Bangkok, said the decision to close schools was made so that parents need not worry.

"When the schools are closed, parents don't have to leave homes to send their kids off to schools," Kwanmuang said.

The governor said that about 50 drones would be deployed in the Bangkok area on Thursday in a bid to ease the ongoing smog by spraying water mixed with molasses to catch the particles in the air.

Earlier this month, officials tried to resolve the poor air quality by spraying water for three days and they're also trying to produce artificial rain, government departments have said. Authorities are also continuing to spray water from fire trucks on the capital's choked streets.

Related: How to manage the polluted air you breathe

The move has prompted a mixed reaction from residents on social media platforms; some argue it would have been better for students to remain indoors at school, pointing out that the closures have forced parents to take time off work to look after children.

Others praised the decision, saying some schools lack air conditioning, or are semi open-air. Keeping schools open could thus be dangerous for the children.

Poor air pollution could not come at a worse time for the country's tourism sector, with the Chinese Lunar New Year just days away. Thailand is already struggling to win back Chinese vacationers following the deadly boat accident in the waters off the resort island of Phuket last July.

China is the biggest source of foreign visitors to Thailand, where tourism is a major industry. Almost 10 million Chinese nationals visited Thailand last year, according to official statistics.