Chiang Rai: The Pollution Control Department has revealed concerning results from sediment tests in the Kok River, its tributaries, and the Mekong River, conducted between March and April.
According to Thai News Agency, these tests found arsenic, lead, and other heavy metals exceeding safe levels for benthic animals, posing potential health risks for villagers consuming fish from these areas over the long term.
The sediment measurements, carried out by the Pollution Control Department (PCD) under the Ministry of Natural Resources and Environment, highlighted significant contamination along the upper Kok River near the Thai-Myanmar border and the Chalermprakiat 1 Bridge in Chiang Rai City. Key areas of concern where arsenic concentrations surpass safe standards include Tha Ton Subdistrict in Mae Ai District, Chiang Mai Province (KK01), Mae Salak House (KK03), and Chalermprakiat Bridge 1 in Mueang Chiang Rai District (KK09). Downstream locations, such as Saphan Yonok Nakhon (KK12) and Ban Saeo Subdistrict in Chiang Saen District (KK15), exhibited arsenic levels below the standard.
Lead levels also exceeded safe thresholds for benthic animals at several sites, including KK03, KK04, and KK09, but have not yet posed direct risks to human health. Tributaries like the Fang River, Korn River, Lao River, and Suai River recorded elevated nickel, arsenic, and chromium levels in certain areas, notably the Korn River (KO01).
In the Mekong River, particularly in Chiang Saen District (NK01-NK02), arsenic levels exceeded standard limits, likely due to contaminated tributaries feeding into it. The PCD noted that sedimentation has increased as the water flow through the Chiang Rai weir has slowed, causing lower arsenic levels downstream of the weir.
The PCD acknowledges the current lack of long-term data, having conducted only two rounds of measurements without an existing database. Continued monitoring and analysis are underway to establish guidelines for future management. The department remains vigilant regarding the potential cumulative health effects on locals consuming fish from contaminated areas.
In response, Mr. Chalermchai Sri-on, Minister of Natural Resources and Environment, has directed the Ministry’s Permanent Secretary, Mr. Chatuporn Buruspat, to convene an urgent meeting on June 4 to address the situation. The meeting aims to expedite domestic surveillance measures and impact reduction strategies, such as implementing a sediment trap system, while international cooperation to tackle the problem’s root cause progresses.