Choking air pollution continues to cloud roads in northern Thailand as residents urge authorities to declare the area a 'disaster zone'.

An apocalyptic orange haze shrouded the Mueang Chiang Rai district of Chiang Rai province on March 28, obscuring the sun as it blanketed buildings and homes.

Residents and business owners in the region have called on local officials to declare the district a disaster zone. The designation will allow the rapid mobilisation of emergency resources.

However, both Chiang Rai governor Puttipong Sirimat and Interior Minister Anupong Paochinda refused, fearing the 'negative impact' of such labels.

Interior Minister Anupong added there was no clear PM2.5 dust threshold to declare a disaster because the pollution levels change constantly.

He said he has asked provincial governments to coordinate with the Ministry of Natural Resources and Environment to deal with the smog, which he said were mostly caused by forest fires in nature reserves.

Dr. Watchapong Kamla, Chiang Rai provincial health chief, said that 3,478 people have visited hospitals to be treated for respiratory conditions from March 19 to 26.

Yesterday, the average PM2.5 levels in the province reached an alarming 523 micrograms per cubic metre in the Mae Sai district - more than tenfold the 'safe' PM2.5 threshold of 50 micrograms per cubic metre in Thailand.

Scientists found that smog is at its worst in the country when farmers burn waste crops to cheaply clear their land between late October and April. This is combined with high numbers of polluting cars on the road and large construction projects across the capital.

The seasonal lack of wind and rain, combined with a winter low-pressure system in which cold air is trapped closer to the ground by warm air above – prevent the pollution from being dispersed naturally.

The Thai government has been criticised for failing to tackle the country's air pollution crisis, with bizarre measures such as spraying water into the air and giant purifiers having no impact.

Data scientist engineer Worasom Kundhikanjana said: 'PM 2.5 pollution has a seasonal trend in Bangkok and the northern provinces, but has only recently received public attention. During this winter haze, the harmful particle pollution level is high throughout the day, including on weekends.

'Unfortunately, spraying water into the air does not appear to be effective, since the volume of water is minuscule compared to actual rain.

'With the start of the monsoon season, the weather in Bangkok will get better, and public attention on this issue will likely fade. However, without immediate policy measures, the problem will come back again next winter.'