Sai River Arsenic 28 Times Limit; Mae Sai Water Plant Shut, 79 Contaminated
Arsenic contamination in the Sai River has reached 28 times the safety standard, forcing the Mae Sai waterworks to halt production and affecting over 60,000 rai of agricultural land. Rice grown with the polluted water also exceeds arsenic limits, and urine tests have confirmed unsafe arsenic levels in 79 residents across seven northern and northeastern provinces. The pollution is linked to cross-border mining operations using Thailand as a transit route, with critics accusing the government of failing to tackle the source.
MP Phattharaphong Lilaphat of the Prachachon Party from Chiang Mai has exposed an arsenic crisis in the Sai River, where contamination levels exceed safety standards by 28 times, rendering the Mae Sai waterworks unable to produce tap water. Tests over the past year and a half have consistently found arsenic above limits, with the latest reading 28 times the standard and turbidity exceeding 10,000 NTU — beyond treatment capacity. The polluted river irrigates over 60,000 rai of farmland, and rice samples have also tested above arsenic standards. Urine tests across Chiang Mai, Chiang Rai, Mae Hong Son, Loei, Bueng Kan, Nakhon Phanom, and Nong Khai have detected unsafe arsenic levels in 79 people. The problem, traced to mining operations in neighboring countries using Thailand as a transit route to China, has now entered the food chain and human bodies while the government fails to address the root cause. Affected communities span Mae Sai and Mueang districts in Chiang Rai (Sai and Kok rivers), Mae Ai district in Chiang Mai (Ruak river), Mae Hong Son province (Salawin river), and upper Northeastern provinces along the Mekong River, all facing a severe and worsening crisis.
