Ecologists are warning that mainland Southeast Asia faces a looming ecological disaster unless urgent steps are taken to address the rare-earth mining boom in war-torn Myanmar. According to Global Witness, a London-based watchdog, Myanmar has become the world's largest source of heavy rare-earth elements. These minerals are essential for manufacturing high-tech products like wind turbines, electric vehicles and medical devices. Most of these mines are located in Shan state, where civil war has raged since the 2021 military coup. Earlier this year, Thailand's Department of Pollution Control found arsenic levels nearly four times higher than World Health Organization (WHO) limits in parts of the Kok River, a Mekong tributary flowing into Thailand from Myanmar. Other toxic metals were also detected at dangerous levels. A mining site on the slopes of a mountain in Myanmar's Kachin Special Region 1A mining site on the slopes of a mountain in Myanmar's Kachin Special Region 1 Rare-earth mining has exploded in Myanmar's Kachin region, making it the world's largest source of supplyImage: Supplied by a Global Witness partner The Kok runs through northern Thailand's Chiang Rai province before merging with the Mekong, where arsenic concentrations have also reportedly been detected. The Mekong is Southeast Asia's longest river, which provides a lifeline for millions. Experts fear the contamination could seep into irrigation systems that feed vast stretches of the region's farmland and drinking water supplies. The WHO has reportedthat prolonged exposure to arsenic and other metals can cause cancer, neurological disorders and organ failure. "What we see now is just the beginning," Pianporn Deetes, campaigns director at International Rivers, a conservation NGO, told DW. "If left unchecked, the situation could deteriorate rapidly — potentially hundreds of unregulated mines upstream, heavy contamination spreading through the Mekong and its tributaries, and ultimately acidification of waters reaching as far as the seas," she said. Limited options After petitions from local communities in June, Thai authorities proposed building underwater sediment barriers or mini-dams on the Kok to trap toxic deposits before they reach villages. Environmental groups say such infrastructure will take years to complete, while the crisis is already unfolding. Bangkok has few options. The problem lies largely within Myanmar's borders, particularly in Shan state, where new mines are located in territory controlled by the United Wa State Army (UWSA), a powerful China-backed militia that oversees two semi-autonomous enclaves. Reuters has reported that the UWSA provides armed protection for Chinese-run mining operations there. Neither Myanmar's military rulers nor international organizations exert meaningful control over the region. Currently, it is unknown whether the pollution has remained concentrated in northern Thailand or whether it has already leached into the Mekong, potentially affecting downstream nations.