Rare Earth Mining in Myanmar Contaminates Thai Rivers and Food Supply with Arsenic and Heavy Metals

Arsenic and heavy metals originating from roughly 577 rare earth mines in Myanmar's Shan and Kachin states are flowing downstream into northern Thailand, contaminating the rivers, farmland, and food supply of communities in Chiang Rai and Chiang Mai. Water samples collected at Tha Ton — where the Kok River enters Thailand — showed arsenic at 0.0159 mg/L, above the 0.01 mg/L safety standard, while samples from Chiang Rai measured approximately 0.03 mg/L, three times the limit. In March 2025, Thailand's Pollution Control Department detected arsenic in Mekong River sediment at up to 296 mg/kg, nine times the 33 mg/kg safety threshold. A local farmer's urine tests show arsenic at double the acceptable exposure limit, and deformed or lesion-bearing fish have been caught in the affected rivers, with scientists suggesting heavy metals may be suppressing fish immune systems. The mines, many financed by Chinese companies and operated with Chinese technical expertise, expanded into Myanmar after China tightened its own environmental standards in the mid-2010s; Myanmar is now the world's fourth-largest rare earth producer and China's biggest external supplier. Thailand is pursuing diplomatic solutions involving Australia and Japan as intermediaries, and is exploring automated water-monitoring systems, but officials acknowledge there are no legal mechanisms to compel Myanmar or China to act. Experts argue that meaningful change requires China — whose influence over both the Myanmar military and ethnic armed groups is significant — to set and enforce environmental standards for its overseas mining operations.