Fine dust levels have risen slightly in greater Bangkok, but Bang Khen district of the capital was the only area with a hazardous reading, the Pollution Control Department reported on Tuesday morning.
The levels of particulate matter 2.5 micrometres and less in diameter (PM2.5) ranged from 18 to 55 microgrammes per cubic metre of air in the past 24 hours in greater Bangkok. Thailand has set the safety threshold at 50mcg.
The lowest level was on Phetkasem Road in Phasicharoen district of Bangkok and the highest on Phahon Yothin Road in Bang Khen.
The department expected PM2.5 levels to drop on Wednesday.
The morning report said road cleaning and enforcement of controls on vehicles emitting black exhaust smoke continued. On the first three days of this month, officials banned the use of 161vehicles and required the improvement of 72 others for excessive emissions.
The Bangkok Metropolitan Administration said it installed sprinklers to reduce fine dust at all its hospitals and all except five schools, where installation was not possible.
Prime Minister Prayut Chan-o-cha announced on Tuesday afternoon that about 600 of the roughly 100,000 factories nationwide had been ordered to halt operations and improve pollution controls to reduce fine dust emissions, mainly from burners used to boil water.
He also said about 50% of the particulate matter in the city air came from vehicle exhaust emissions. He wanted this lowered to 35%.
The Transport Ministry had been instructed to strictly enforce diesel engine standards and ensure vehicles were fitted with catalytic converters to reduce air pollution.
