The annual risk rate for lung cancer among the population in the North is now 40 per 100,000 people - compared to 20 per 100,000 people in other regions, said Assoc Professor Phongthep Wiwatthanadej.

Up to 600 Chiang Mai residents will face lung cancer risk each year, out of a total population of 1.7 million people living in this northern province.

Phongthep said his theory was not supported yet by any research, but said the constant smog exposure had subjected Chiang Mai locals to lung cancer risk, especially those living in Saraphee district, where the highest risk rate was reported.

The rate suffered by women in the district was one the highest in the world, he said without elaborating.

The doctor was speaking at a local seminar held by Chiang Mai University to address the ongoing smog, which is now covering the province more heavily, causing greater health concerns for locals.

More and more cases of hospital treatment for those suffering from smog are reported, which mostly involves respiratory problems and irritation to patients' eyes.

The other provinces affected by the smog, which is caused by forest and manmade fires, are Lampang, Lamphun, Uttaradit, Phitsanulok, Sukhothai and Phetchabun.

Part of the smog is travelling from Burma.

Duangjan Arphawatcharut, a CMU researcher, said honey producers and bee farmers suffered a 70percent loss in revenue after flowers bloomed for only two days before the smog hit the North.

Global warming had been already disturbing the bees' activities beforehand.

In neighbouring Chiang Rai, the safety status will be announced in areas where dust density exceeds a safe level of 200 micrograms per cubic meter.

The existing dust density level is now far from reaching that stage but local civil disaster officers are monitoring the situation.

-The Nation / Asia News Network