Northern Thailand has been branded a "disaster zone" as air pollution in the region from agricultural burning soared to the highest levels in the world.

Footage shows ‘very unhealthy' Chiang Mai this morning, with the AQI ranking at 289 - with 239 micrograms of PM2.5 particles per cubic metre of air. The safe level is 50.

Chiang Mai and Chiang Rai - two of the country's most popular city destinations - have been enveloped in a toxic haze for several months, with business owners and residents now urging the local government to declare the district a "disaster area".

The designation would allow resources to be mobilised quickly to address the hazardous PM2.5 dust levels, which have been responsible for thousands of hospital admissions.

However, defiant Chiang Rai governor Puttipong Sirimat and Interior Minister Anupong Paochinda refused to address the issue, fearing the "negative impact" of the label on tourism.

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 was mostly caused by forest fires in reserves.

Swiss air quality company IQAir today ranked Chiang Mai as the "most polluted city in the world".

The province registered a "very unhealthy" air quality index (AQI) of 289, with 239 micrograms per cubic metre of PM2.5 particles - well above the safe level of 50.

Chiang Mai residents seeking treatment for respiratory illnesses at hospitals have reportedly been turned away due to full occupancy.

While hospital data from Chiang Rai shows that more than 3,500 people were admitted for respiratory issues in that city alone. They had sore throats and nasal irritation - symptoms that can lead to killer lung diseases in the long term.

Associate Professor Chalerm Liwsrisakun, head of the Department of Internal Medicine at Chiang Rai University's Faculty of Medicine, said short-term effects of the air pollution may include burning eyes or noses, throat irritation, nosebleeds, and itchy skin.

Prolonged exposure, he added, may lead to decreased lung function and increased lung cancer risk.

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. It has been worsened in recent years by rising demand for food and agro-business lobbyists that can stifle the government's control over farmers.

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 – hampers the pollution from being dispersed naturally by the wind.

The notoriously corrupt 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".

Northern Thailand has been branded a 'disaster zone' as air pollution in the region from agricultural burning soared to the highest levels in the world.

Footage shows ‘very unhealthy' Chiang Mai this morning, with the AQI ranking at 289 - with 239 micrograms of PM2.5 particles per cubic metre of air. The safe level is 50.

Chiang Mai and Chiang Rai - two of the country's most popular city destinations - have been enveloped in a toxic haze for several months, with business owners and residents now urging the local government to declare the district a 'disaster area'.

The designation would allow resources to be mobilised quickly to address the hazardous PM2.5 dust levels, which have been responsible for thousands of hospital admissions.

However, defiant Chiang Rai governor Puttipong Sirimat and Interior Minister Anupong Paochinda refused to address the 'disaster zone' issue, fearing the 'negative impact' of the label on tourism.

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 reserves.

Swiss air quality company IQAir today ranked Chiang Mai as the 'most polluted city in the world.'

The province registered a 'very unhealthy' air quality index (AQI) of 289, with 239 micrograms per cubic metre of PM2.5 particles - well above the safe level of 50.

Chiang Mai residents seeking treatment for respiratory illnesses at hospitals have reportedly been turned away due to full occupancy.

While hospital data from Chiang Rai shows that more than 3,500 people were admitted for respiratory issues in that city alone. They had sore throats and nasal irritation - symptoms that can lead to killer lung diseases in the long term.

Associate Professor Chalerm Liwsrisakun, head of the Department of Internal Medicine at Chiang Rai University's Faculty of Medicine, said short-term effects of the air pollution may include burning eyes or noses, throat irritation, nosebleeds, and itchy skin.

Prolonged exposure, he added, may lead to decreased lung function and increased lung cancer risk.

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. It has been worsened in recent years by rising demand for food and agro-business lobbyists that can stifle the government's control over farmers.

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 – hampers the pollution from being dispersed naturally by wind.

The notoriously corrupt 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.'