Rainmaking to the east of Bangkok has led to a dramatic drop in air pollution in the capital and its surrounds, with ultra-fine dust levels in all areas back within the safety threshold on Monday.
Department of Rainmaking and Agricultural Aviation director-general Supis Pitaktham said a rainmaking operation had been launched from Dec 16-18 in areas east of Bangkok after high PM2.5 dust levels during the past week had started affecting people's health.
On Dec 16, two Cessna Caravan aircraft performed two rounds of cloud seeding flights over Ban Bung district of Chon Buri and Khong Khuan district of Chachoengsao. This caused the clouds to thicken. As a result, PM2.5 levels in Bangkok and east of Samut Prakan, Chon Buri and Chachoengsao provinces all fell.
On Sunday, the two planes made two rounds of rainmaking flights over Phanom Sarakham district of Chachoengsao and Pak Phli district of Nakhon Nayok. As a result, there was a little rain in Ongkharak district of Nakhon Nayok and Nong Sua district of Pathum Thani.
Mr Supis said the operation caused rain clouds in the east to move over Bangkok. As a result, the PM2.5 situation improved on Monday morning.
According to a Department of Pollution Control report, PM2.5 levels in Bangkok and nearby provinces were within the safety threshold on Monday morning.
He said the rainmaking operation for Bangkok and its proximity must be carefully planned. If the wind blows from the east, the operation must be based in Rayong province. If the wind is from the west, it must be based in Kanchanaburi.
The rainmaking aircraft must operate at least 70 nautical miles from Suvarnabhumi and Don Mueang airports, to meet international aviation rules, he said.