A thick layer of haze from slash and burn farming that has blanketed Chiang Mai's Muang district has prevented four flights from landing in the city's airport and poses health risks to city residents.
Staff at Chiang Mai airport confirmed Monday Thai Airways flight TG 106 from Suvarnabhumi airport and Thai Lion Air flight SL8504 from Don Mueang airport were forced to return to the capital between 11.40am and 12.05pm due to worsening haze conditions in Muang district.
Meanwhile, two other flights, Bangkok Airways flight PG241 from Samui of Surat Thani and Air Asia flight FD3161 from Phuket were diverted to land in Chiang Rai between 12.10pm and 12.30pm.
Flight diversions, worsening health problems among locals, and a rash of tourist cancellations stemming from the haze problem are increasing the economic cost of the farmer burn-offs, with authorities now threatening to take legal action against farms if the problem gets any worse.
The haze has affected visibility in many areas of Muang district, limiting visibility on tall buildings and Doi Suthep to between 500-1,000 metres Monday morning.
Data from a pollution control unit at Yupparaj Wittayalai School showed that airborne particulate matter, or PM10, in Muang district stood at 258 microgrammes per cubic metre, exceeding the maximum safety threshold at 120 microgrammes.
Residents have complained of eye and nose irritations as the majority of them did not wear masks when they went outside, according health authorities.
They said more than 37,000 people have sought treatment for respiratory problems at community clinics since the start of this month.
Health authorities warned about the danger of haze pollution, advising residents to wear a mask when they go outdoors. Children, the elderly and patients should stay indoors to protect themselves, he said.
Natural Resources and Environment Minister Dapong Ratanasuwan said Monday Mae Chaem district was the worst hit by thick smog caused by farmers' forest fires.
Gen Dapong and his team had made an aerial inspection over Chiang Mai and said fires could be observed in at least 10 locations.
The smoke had caused visibility to drop during the inspection, he said, adding water had to be sprayed in the air to clear a path.
Gen Dapong said the ministry and officials representing 10 northern provinces had discussed to decide what to do about long-standing haze problems. The authorities had agreed to take legal action if needed against farmers burning off unwanted weeds, he said.
Pornchai Jitnawasatian, president of the Association of Tourism in Chiang Mai, said Chiang Mai has witnessed the worst haze this year. A number of tourists, especially those from Europe and America, have cancelled their trips to the province after the situation has grown worse.
Meanwhile, the worst haze conditions were reported in Mae Hong Son province where airborne particulate matter stood at 303 microgrammes per cubic metre, followed by Chiang Rai with 300 mcg, Chiang Mai with 258mcg, Phayao 251mcg, Lamphun 180mcg, Lampang 161mcg, Phrae 137 mcg, Nan 133mcg and Tak 132 mcg.