Arsenic Contamination in Kok and Sai Rivers : Do Something about it.

Widespread Arsenic Contamination in Northern Thai Rivers Linked to Myanmar Mining Operations

News has it that at least rivers in northern Thailand, particularly those flowing from neighboring Myanmar, are facing a growing crisis of arsenic contamination, with recent tests revealing levels of the toxic heavy metal far exceeding national safety standards. 

The pollution, widely attributed to unregulated mining activities in Myanmar's Shan State, poses a significant threat to the environment, public health, and local livelihoods in the provinces of Chiang Mai and Chiang Rai.

The Kok and Sai rivers, both of which originate in Myanmar and are vital water sources for communities in northern Thailand, have been found to contain alarming concentrations of arsenic. According to Thailand's Pollution Control Department, water samples collected in May and June 2025 from multiple points along these rivers showed arsenic levels consistently above the permissible limit of 0.01 milligrams per liter (mg/L). In some areas of the Sai River, readings have been as high as 49 times the safety standard.

The primary source of the contamination is believed to be from extensive gold and rare earth element mining operations in Shan State, a region largely outside the full control of the Myanmar central government. Reports suggest that Chinese investors are heavily involved in these mining activities, which often lack proper environmental regulations and waste management practices. Toxic substances, including arsenic, are likely being discharged directly into waterways that flow into Thailand.

The environmental consequences are already visible. The once-clear waters of the Kok and Sai rivers have become murky, and there have been widespread reports of mass fish deaths and fish with ulcers and other abnormalities. This has had a devastating impact on local fishing communities who depend on the rivers for their sustenance and income. The contamination also threatens the broader ecosystem of the Mekong River, into which both the Kok and Sai rivers eventually flow.

Health officials have issued warnings to local residents, advising them to avoid using the river water for consumption, bathing, or other domestic purposes. Arsenic is a known carcinogen, and long-term exposure can lead to a range of serious health problems, including skin lesions, cardiovascular disease, and various forms of cancer. Residents in affected areas have already reported incidents of skin rashes and other irritations after coming into contact with the contaminated water.

The Thai government has acknowledged the severity of the situation and has been actively monitoring water quality. In response to the crisis, there have been proposals to construct dams and weirs to help filter and trap the heavy metal contaminants. However, many experts and environmental groups argue that these are temporary solutions and that the problem must be addressed at its source.

The transboundary nature of the pollution presents a significant diplomatic challenge. Thai authorities have expressed their intention to engage in dialogue with their counterparts in Myanmar and China to find a sustainable solution. However, the complex political landscape in Myanmar's border regions makes direct intervention and regulation of the mining operations difficult.

As the monsoon season progresses, there are concerns that heavy rainfall could exacerbate the pollution by washing more contaminated sediment downstream, further elevating arsenic levels in the rivers and posing a continued threat to the well-being of communities and the delicate riverine ecosystems of northern Thailand.