Authorities in Bangkok ordered nearly 450 schools to close yesterday as pollution levels in the Thai capital reached dangerously unhealthy levels.
Bangkok, the world's most visited city, saw levels of PM 2.5 particles at 78.3 pg/m3. A level above 35 is considered unhealthy, according to independent air quality monitor AirVisual.
PM 2.5 particles can include dust, soot and smoke and are so small they can lodge deep in the lungs and enter the bloodstream.
Bangkok's air quality index yesterday was 163, according to data from AirVisual. Anything above 150 is considered unhealthy.