Cancer-causing air pollution soared as more fires were detected in northern Thailand.

Chiang Mai ranked fifth in the world for air pollution according to Swiss air quality technology company IQAir as 54 'hotspots' were detected in the province on March 26.

Footage shows a white haze blanketing roads in the city on Tuesday morning.

IQAir reported that Chiang Mai had an air quality index (AQI) of 171 indicating 'unhealthy' levels, while the levels of delay PM 2.5 particles were at 94 microgrammes per cubic metre.

Meanwhile, data from Thailand's Pollution Control Department showed that air pollution was highest in the Hang Dong of Hot district, which saw PM 2.5 levels of 117.5 microgrammes per cubic metre.

Local media reported that recent rains had helped clear the smog. However, authorities said they were on alert as increasingly dry conditions could lead to wildfires.

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.