Safety
Pollution Control Department Reports Elevated Arsenic Levels in Northern Rivers
The Thai Pollution Control Department has detected arsenic levels exceeding safety standards for aquatic life in the Kok, Ruak, and Mekong rivers following recent sediment testing.
On August 21, 2026, Thailand’s Pollution Control Department (PCD) released the findings of its 12th sediment quality assessment, conducted between July 7 and 10, 2026. The study, which examined 21 locations, was initiated to investigate reports of abnormal turbidity in the Kok River across Chiang Mai and Chiang Rai provinces.
The report indicates that arsenic concentrations in several areas of the Kok River exceeded the safety threshold of 10 milligrams per kilogram (mg/kg) for benthic organisms. Notable findings include 23 mg/kg at the Thai-Myanmar border near Ban Kaeng Tum and 11 mg/kg near the Mae Yao-Doi Hang Friendship Bridge. Additionally, the latter site recorded mercury levels of 0.21 mg/kg, which also surpasses the established safety standard for aquatic life.
For residents and travelers in these regions, these findings highlight ongoing environmental monitoring efforts regarding water and sediment quality. While the PCD has identified these specific chemical concentrations, the report focuses on the impact on benthic organisms. It remains to be confirmed how these sediment levels correlate with broader water quality safety for human recreational use or consumption, as the current data specifically addresses sediment standards. Authorities continue to monitor the situation to determine the long-term implications for the river ecosystems.