Thailand's Ministry of Education has ordered all schools in Bangkok and some surrounding provinces to close for the remainder of the week amid concerns over dangerous levels of air pollution.
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.