On May 30, Chiang Rai Governor Charin Thongsuk ordered public health officials to investigate potential arsenic contamination in water sources in the Tham Phachom community, Wiang Phang Kham Subdistrict, Mae Sai District—near the Thai-Myanmar border. Residents had reported skin rashes after using local water, prompting concern.
Officials collected samples from surface water, shallow wells, and groundwater for arsenic testing using a field test kit. Preliminary results found arsenic levels within safety limits (not exceeding 0.01 mg/m³). No neurological abnormalities were found in individuals with rashes, which were diagnosed as sweat-induced allergic reactions. However, six additional water samples were sent to Chiang Rai’s Medical Science Center for laboratory analysis, with results expected in 3–5 days. Residents were advised to avoid using untreated natural water and seek medical attention for symptoms such as rashes, fatigue, or discolored urine.
Previously, on May 29, researchers from Mae Fah Luang University had conducted independent tests on shallow wells in the same area and found arsenic levels between 0.06–0.12 mg/m³, exceeding the legal limit. They attributed the discrepancy to different test methods used.
Mrs. Pawawan Somphan, 72, a long-time resident, said her household had used well water for decades without issues until recent flooding caused turbidity. Despite no visible symptoms, she switched to bottled water after learning about arsenic contamination and is now seeking reconnection to the public water supply, which previously had inconsistent service.
Mae Sai District Chief Warayut Khombun confirmed that official testing by health authorities had not yet shown dangerous contamination levels, urging the public not to panic based on unofficial reports. Final actions will depend on lab-confirmed results.
Associate Professor Dr. Surapol Worapatratorn from Mae Fah Luang University noted that high heavy metal contamination in the Sai River and shallow wells near it (5–10 meters deep) poses health risks. He emphasized the need for ongoing water quality monitoring and government-led public advisories until official results are available.