PUBLISHED : 23 Nov 2025 at 06:06
MAE HONG SON: The Pollution Control Department (PCD) has detected arsenic contamination above safety limits at all 13 monitoring points along the Salween River in Mae Hong Son, following reports of unusually cloudy water.
PCD director-general Surin Worakijthamrong said officials collected water and sediment samples between Nov 12 and 13 along the Thai-Myanmar border, from Mae Sariang to Sop Moei district.
Laboratory tests showed arsenic levels exceeding the standard of 0.01 milligrammes per litre at every site. Lead contamination above the 0.05 mg/L limit was found at one location, while mercury levels were within safety limits.
Water samples taken from five tributary sites were also tested and all met water-quality standards, he said. Mr Surin said the Natural Resources and Environment Ministry will ask the Foreign Ministry to notify Myanmar and request an investigation into potential pollution sources upstream.