Chiang Rai:The Pollution Control Department has raised a high alert after releasing results from its 23rd water test, indicating that arsenic levels in the Sai River continue to surpass acceptable standards at all monitoring points.
According to Thai News Agency, the latest water quality report highlights that while arsenic levels in the Sai River remain above the standard, the Kok and Mekong Rivers have heavy metal levels within safe limits. The Pollution Control Department of the Ministry of Natural Resources and Environment conducted the 23rd surface water quality monitoring survey. Water samples were collected from 23 monitoring points in Chiang Mai and Chiang Rai provinces between September 26 and 30, 2026, to observe any abnormal turbidity and heavy metal contamination.
The findings revealed that the Mae Sai River is a high-risk area needing meticulous monitoring, as arsenic levels exceeding the surface water quality standard (set at no more than 0.010 milligrams per liter) were detected at all monitoring points. Specific sites included Ban Hua Fai (0.017 mg/L), the Second Friendship Bridge (0.013 mg/L), and Ban Pa Sang Ngam in Mae Sai District (0.012 mg/L).
In contrast, water quality in the Kok River, stretching from the Thai-Myanmar border in Mae Ai District, Chiang Mai Province, to Chiang Saen District, Chiang Rai Province, showed no contamination beyond acceptable levels, with arsenic and other heavy metals remaining within safe parameters.
Additionally, assessments of the Ruak River, the Mekong River, and tributaries of the Kok River, such as the Fang River, Lao River, and Korn River, confirmed that heavy metal levels were within the standard limits.
The Pollution Control Department has assured that it will continue to monitor and conduct random inspections of water quality in the northern region's river basins, consistently reporting results to the public to enhance confidence and mitigate health impacts on local residents.