Footage shows cancer-causing air pollution in one of Thailand's most popular tourist city - with environment groups ranking it as the worst in the world.

Levels of the deadly PM 2.5 particles caused by agricultural burning - that the country's bungling governments have failed to stop since 2017 - have soared to more than 25 times the safe levels in recent days.

It puts the once-idyllic mountain region below Delhi, Iraq and Pakistan on charts compiled by Swiss group IQAir.

Levels of the killer particles on Monday, March 18, were at 135 microgrammes per cubic metre of air. The safe level set by the World Health Organisation is five microgrammes.

Government leader Srettha Thavisin, who was not directly elected but backed by disgraced mogul Thaksin Shinawatra following a de facto election coup last year, dismissed calls for the region to be declared a disaster zone as it would 'hurt tourism'.

He said: 'What will happen after the announcement is it will affect the number of foreign tourists when tourism has just recovered. Chiang Mai province will definitely lose tourists who plan for short- and long-term stays. That is what we are worrying about.'

Officials said more than 10 million people had been treated for pollution-related illnesses in Thailand in 2023.

Dangerous levels of deadly PM 2.5 particles - which cause cancer and other debilitating illnesses - are recorded every year in Thailand between December and April.

Despite paying lip service for several years, politicians have failed to stop individuals from burning their land due to it being cheaper and easier than modern farming methods.

In March 2023, the Public Health Ministry of Thailand reported that around 1.3 million people in the country had been unwell due to the rising levels of air pollution. Officials said 200,000 residents were hospitalised in a single week.

They warned hospitals in December 2023 to prepare for an influx of patients.

It came as researchers from Peking University in Beijing, China, also discovered that long-term exposure to particulate matter PM.25 air pollution is associated with an increased risk of lung cancer.

In December, Dr Krittai Thanasombatkul from Chiang Mai, Thailand, died of lung cancer. He had previously blamed PM 2.5 microdust particles for his condition.

The New York State Department of Health say PM 2.5 increases the risk of heart disease, asthma, and low birth weight.

While medics from South Korea published research in the National Institute of Health in the United States that said the pollutant increases the risk of stroke, ischemic heart disease, chronic obstructive pulmonary disease (COPD), lung cancer, and other illnesses such as immune deficiency and even obesity.