About 1,700 people in Chiang Mai on Monday sued the prime minister and two state agencies for failing to tackle the annual smog over the region, which they say is shortening their lives by about five years.

About 60 people were at the Administrative Court in the northern province to file the lawsuit against caretaker Prime Minister Prayut Chan-o-cha, the National Environmental Board and the Securities and Exchange Commission. They accuse them of failing to solve the smog problem in the North.

The approximately 1700 plaintiffs include northern people's networks, activists, academics from Chiang Mai University and local residents.

From Friday to Sunday last week, 727 people signed their names in support of the lawsuit at the faculty of law, Chiang Mai University, and about 980 people did so online. The plaintiffs blamed contract farming for the devastating air pollution.

One of the the plaintiffs said the prime minister failed to fully use his power to solve the problem.

The plaintiffs accuse the National Environmental Board of failing to effectively implement the national plan to tackle pollution introduced in 2019.

The Securities and Exchange Commission was held responsible for failing to examine the sources of pollution within the supply chains of major listed companies.

Dr Rangsarit Kanchanawanit from the faculty of medicine at Chiang Mai University said the health of people in urban areas was suffering from the unsafe levels of PM2.5. The pollution level raised the risk of lung cancer, heart disease and stroke, and shortened people's lifespans by 4-5 years.