Firefighters tackled a fire caused by illegal burning that broke out on a mountain in northern Thailand.

More than 50 firemen, volunteers, and soldiers were dispatched to the Suthep Scout Camp to combat the blaze burning through Doi Suthep mountain in Chiang Mai province at around 9 pm on April 17.

Phuphichit Chuaybamrung, chief of the Doi Suthep-Pui National Park, said the flames were extinguished at around 1 am. Officers believe the fire was started by villagers, who set fires to clear vegetation for planting crops or to drive out wild animals to catch.

He said: 'The fire burned around 60 rai of land within four hours. We believe it was caused by illegal burning by hunters.'

The resulting smoke added to the already worsening air quality in Chiang Mai, which saw 'unhealthy' levels of PM2.5 fine dust at 94.6 µg/m³.

Chiang Mai has been consistently rated the worst city in the world for air pollution by Swiss group IQAir.

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 when farmers across Southeast Asia burn waste crops to clear their land.

The rudimentary method, known as 'slash and burn', is quicker and cheaper than modern machinery, leaving relatively poor landowners unwilling to heed environmental and health concerns over economic necessity.

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.

Researchers from Peking University in Beijing, China, found that exposure to PM 2.5 air pollution is associated with an increased risk of lung cancer.

In December, Dr Krittai Thanasombatkul from Chiang Mai - one of the world's worst cities for air pollution - died of lung cancer. He had previously blamed PM 2.5 microdust particles for his condition.

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

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.