Southeast Asia’s Toxic Rivers: No Easy Solutions
Scientists warn of a regional disaster If pollution from rare earth and gold mining in Myanmar continues to spread toxins further along the Mekong River.
The Diplomat
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Saffron-robed Buddhist monks led a six-day peace march along the banks of the Kok River on June 6 – U.N. World Environment Day. Their goal was to draw attention to the worsening toxic rivers crisis in northern Thailand.
Pianporn (Pai) Deetes, the director of Rivers and Rights, a Thailand-based foundation dedicated to water security and ecological issues in the Mekong basin, blogged about the march.
“Along the Kok, Sai, Ruak, Mekong, Salween, and Kraburi rivers, communities depend on these waterways for drinking water, fisheries, agriculture, transportation, and cultural identity,” she wrote. “Rivers are not simply part of the landscape here. They are the foundation of life.”
And that “foundation of life” is being poisoned. The plethora of unregulated rare earth and gold mining in Myanmar’s Shan State has caused massive contamination along the transboundary rivers flowing into northern Thailand and thence into the mainstream Mekong River.
Thai Buddhist monks based at Thaton monastery on the contaminated Kok River arrive to a rally after the 68-kilometer Peace March from Thaton to Chiang Rai. Photo by Tom Fawthrop.
“Arsenic contamination carried downstream from rare earth and gold mining sites in Myanmar has now contaminated the river bank sediment,” Dr. Suebsakun Kidnukorn an environmental scientist at Chiang Rai’s Mae Fah Luang University warned, said in an interview. “The PCD [Thailand’s Pollution Control Department] found abnormally high levels on the mainstream Mekong. It entered the food chain with potentially dire consequences for the region.”
Phra Maha Nikhom Mahabhinikkhamano, the assistant abbot of Wat Thaton, led his monks on the 68-kilometer march from Thaton to Chiang Rai. In his address, he urged Thai leaders “to launch a dynamic holistic governmental and diplomatic responseand directly confront the transboundary sources of the pollution.”
The Thai prime minister and six other ministers were all invited to the dialogue forum with the Peace March leaders, which was hosted inside the City Hall by the Chiang Rai’s provincial governor. Not one ranking ministerattended.
“The ministers did not show up because they don’t care,” Niwat Roykaew, founder of The Mekong School and founder of the Chiang Khong Conservation Movement, told The Diplomat.
Niwat Roykaew, a veteran leader of Mekong River conservation and founder of the Mekong School of Indigenous Knowledge, at a protest rally demanding action on river pollution. Photo by Tom Fawthrop.
A winner of the Goldman Environmental Prize, Niwat Roykeaw added, “It is a contradiction that the government still promotes tourism and downplays the health risks from water contamination when they know government data collected by their PCD showed it was not safe to use the river.” The Thai PCD website reported very high levels of arsenic embedded in river sediment.
Natural Resources and Environment Minister Suchart Chomklin and PCD Director-General Surin Worakijthamrong both recognized a need to restore public trust, which is why the PCD is seeking an emergency budgetto install 18 automated monitoring stations along the Kok, Mekong, and Salween rivers. But it is not a done deal, until the Thai prime minister has approved the budget.
This is no longer just an issue of water quality, according to Chiang Mai University environmental scientist Dr. Wan Wiriya. The big worry now, he explained, is that the arsenic has penetrated the river’s sediment and is part of the food base. Once contaminated, toxins will accumulate and magnify through the food chain. Without stronger monitoring and response the impacts will only worsen ,”he said.
Thai scientist Dr Wan Wiriya, whose independent monitoring exposed the worsening ecological crisis and threat to health and and food security. Photo by Tom Fawthrop.
Wan has been carrying out independent water monitoring and a full spectrum of tests on soil and food crops. He explained the scale of the treat: “Arsenic is a silent slow poison. It accumulates in the human body and can cause long-term health impacts.”
In a separate interview, his colleague Dr. Suebsakun elaborated: “It is slow action, it is like smoking cigarettes. At first you don’t notice any problem. But bit by bit you get sick and the cumulative effect can end up with cancer.”Epidemiological evidence shows arsenic induces cancers of the skin, lung, liver, and bladder.
Suebsakun claimed that “the Thai authorities’ response is very weak and lacking in transparency.” He added, “with Thailand’s role in food export promotions and marketing as as ‘The World’s Kitchen,’ you would expect Bangkok authorities to invest more effort to protect the food crops and rice exports from the spread of heavy metal contamination.”
Given the transboundary issues of river contamination along the Mekong, all parties agree that no one country can solve it. The Mekong countries need to cooperate in order to develop solutions.
Pai Deetes, director of the Rivers and Rights Foundation, commented,” The discovery of heavy metal contamination at levels up to nine times above the danger threshold, should trigger immediate regional action.”
But instead of strong regional action, there have been only more attempts to downplay or deny the evidence of a regional crisis, including by the Mekong River Commission (MRC).
The MRC has conducted limited testing in Laos. It concluded in its latest report that “arsenic contamination remains localized but requires sustained attentiondue to its persistence in both water and sediment.”
The MRC officially claims to be a science-based knowledge hub. But Thai scientists were disappointed its report never addressed the wider regional implications posed by the contamination of river sediment and its likely circulation within the food chain.
My visit to Cambodia’s Institute of Technology (ITC) in Phnom Penh in March 2026 was apparently the first time that any international media had interviewed Cambodian scientists on these transboundary threats.
The ITC in Phnom Penh conducts tests to monitor for threats to the ecosystem. Still from a video by Tom Fawthrop/Eureka Films.
The spacious ITC campus has two well-equipped, Japan-funded science laboratories. One of their research and teaching staff, Kaing Vinhteang, had carried out monitoring of water quality, nutrients, and sediment on the Mekong River and the great Tonle Sap Lake.
“We have full capacity to test and analyze pollutants,” Vingteang assured The Diplomat. “In Cambodia we are concerned about the pollutants from upstream countries and the impacts on the downstream.”
Since the border war broke out last year, social media has been dominated by extreme nationalist voices both in Thailand and Cambodia, and there has been very little cooperation between the two neighbors and MRC members.
But the Cambodian scientist insisted that “the river contamination is not a local issue, but a transboundary and regional issue. So if we’re talking about the solution, of course, we cannot act locally. So all Mekong countries, we need to come together to find a solution.”
Thailand-based Dr. Wan also welcomed opportunities to share scientific data with their Cambodian water resource counterparts as a scientific exchange and “people-to-people diplomacy,” bypassing the ongoing bitter border conflict betweenCambodia and Thailand.
However outside of the ITC, other Mekong researchers declined to be interviewed, because they were unaware of any studies on this subject and almost nothing has been published in the Cambodian media.
There are known to be 17 unregulated mine sites in Cambodia and one gold-mining concession that has caused contamination of a river inside the Virachey National Park, in the country’s northeast.
Cambodia needs to upgrade its monitoring to prevent upstream poisoning from reaching the flooded forests of Tonle Sap. Photo by Tom Fawthrop.
China’s Great Power and Great Responsibility
Regional experts recognize that China is the only country that has the capacity to curb the pollution at its source: rare earth mines in Shan State. Not only are the mines themselves controlled by Chinese companies, but the area is under the control of Beijing’s proxy forces, the United Wa State Army.
These environmental safeguards prompted many Chinese companies to move south and set up their operations across the border in Myanmar’s Kachin and Shan states, in order to evade the new environmental regulations.
In Thailand, river conservationists are calling for China to extend their domestic laws to cover unregulated Chinese-run companies operating in Shan State, which are under contract to supply rare earth minerals to China.
“If we cannot stop the dirty mining but you can at least regulate and treat the toxic waste, before the chemicals are dumped into the river,” Wan observed. “This we must do. We want international standards for mining.”
In 2024, China promulgated the “Regulations on the Management of Rare Earths,” the first specific law to regulate the entire rare earth industry supply chain, from mining and extraction to trading, circulation, and reserves. Could rare earth mines in Myanmar become the first test of China’s new laws?
China as a regional leader should play a key role in leading countries to solve this problem, according to Arisara Lekkam, a law lecturer at Chiang Rai’s Mae Fah Luang University.
She views the rare earth mining case in Myanmar as a test of whether the Chinese government is truly prepared to enforce export control laws against its own companies abroad.
For now, China prefers to simply ignore the problem. A press statement from the Chinese embassy in Bangkok that was received by the June 6 peace marchers stated: “We have noted that recent test reports released by the Thai government and relevant authorities show that the water quality of the river meets safety standards in general.”
Suebsakun responded to this claim: “Even if Thai official reports shared with the Chinese embassy in Bangkok claim toxins remain within ‘permissible limits,’ the continuous bioaccumulation poses an insidious, long-term threat to human tissue.”
A drone shot showing the town of Thaton, where the Peace March led by monks started. This area is one of the worst contaminated parts of the Kok River. Photo by Tom Fawthrop.
Meanwhile Bangkok is considering a new budget to replace the tap water supply in Chiang Rai province, covering the Kok River, as well as better monitoring, which has yet to be approved by the Thai prime minister. Thailand has its own incentives to look the other way.
Peoples’ Party MP Phattarapong Leelaphat has reported in parliament that Thai companies profit from minerals and the border trade with Myanmar.
“As chair of the Subcommittee on Transboundary Water Pollution, I have called on the government to provide more information about Thailand’s role as a transit hub for rare earth mining in Myanmar and processing in China,” he stated.
In an email to this author, Phattarapong added, “If the Thai government is serious about coping with transboundary water pollution from mining activities, they should act fast, and raise this issue as a regional environmental disaster, urgent action is needed.”
