79 Residents in 7 Provinces Show Toxic Arsenic Levels
Testing reveals 79 residents across seven northern and northeastern provinces have toxic arsenic levels, with contamination spreading into the Mekong basin and accumulation rising sharply in some areas.
On November 3, 2026, Chiang Mai MP Phattharaphong Lilaphat of the People's Party addressed the situation of arsenic contamination in water sources and its accumulation in residents' bodies. He stated that recent testing found 79 people with toxic inorganic arsenic levels in their urine above safe thresholds across seven provinces in the North and Northeast, indicating the problem is no longer confined to the North but has spread into the Mekong River basin in Isan.
Phattharaphong detailed that the Department of Disease Control found 39 people with excessive arsenic among 520 at-risk individuals along the Mekong: six in Loei, 17 in Nong Khai, six in Bueng Kan, and 10 in Nakhon Phanom. In the North, 40 people exceeded safe levels: 31 in Chiang Rai, seven in Chiang Mai's Khok River area, and two in Mae Hong Son's Salween River area. Results are still pending for residents along the Sai River in Mae Sai district, Chiang Rai, where high arsenic levels have already been detected in water.
The MP expressed concern not only about the rising number of affected people but also that follow-up testing of the same group from the previous year shows arsenic accumulation increasing, particularly in Chiang Mai where levels in the same individuals have more than tripled within a year.
Phattharaphong said he had previously urged the Department of Disease Control to conduct detailed arsenic speciation analysis to separate toxic inorganic arsenic from total arsenic, and to adjust risk-screening criteria to better capture exposure behaviors. The department has implemented these recommendations.
However, he stressed that comprehensive blood testing is still needed — including complete blood counts — and called for the Ministry of Public Health to announce heavy-metal water contamination as a notifiable disease and designate affected areas as environmental disease surveillance, prevention, and control zones.
Phattharaphong said he has tracked and warned the government about this issue for nearly two years. While the Department of Disease Control has acted within its authority, solving the root cause requires government power and decisions. He noted the department's own reports confirm contamination is still spreading and that sufficient source-control measures have not appeared.
"I have exhausted every proposal requiring government authority, yet the government still fails to address the root cause. Reluctance to discuss this internationally means the situation remains unresolved. Today at least 79 people in seven provinces have toxic arsenic levels above safety limits, and in some areas residents' arsenic levels are rising rapidly within just one year," Phattharaphong said.
