Toxic runoff from rare earth mines in Myanmar is poisoning tributaries that feed the Mekong River, reducing fish catches and threatening agricultural output across Thailand, Cambodia, and Vietnam — regions that supply rice, edamame, and garlic to global markets. The mining boom is largely unregulated and centered in Myanmar's conflict zone, making regional coordination on cleanup nearly impossible. AP's reporting is grounded in on-the-ground fieldwork with affected fishermen and farmers, plus expert analysis from regional universities.