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Mekong Communities at Risk as Arsenic Levels Soar in Northern Thai Rivers, Researcher Found

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Arsenic levels up to 19 times higher than safety limits have contaminated rivers feeding into the Mekong, putting downstream communities across Southeast Asia at risk.

The findings come from researchers from Thailand’s Mae Fah Luang University and the Northern Natural Disaster Research and Prediction Institute who uncovered the contamination during a field survey on 30 April

Led by Suebsakunl Kidnukorn and Surapol Vorapatratorn, the team collected water samples from nine sites along the Sai, Ruak, and Mekong rivers in Chiang Rai Province, Thailand, after flash floods swept through the region the day before.

They noticed unusual residue along the banks of the Sai River, prompting further investigation. Laboratory tests later confirmed dangerously high arsenic levels in most of the sampled sites. Arsenic, a toxic metal, can cause serious long-term health issues, including cancer.

Eight of the nine test sites exceeded the World Health Organization’s safety threshold of 0.01 milligrams per litre. 

The Sai River near Thamphachhom-Hua Fai and the 1st Thai–Myanmar Friendship Bridge both recorded levels of 0.14 milligrams per litre. An irrigation canal in Mueang Daeng village showed 0.18. The Ruak River near Vienghom and Sopruak villages, and the Sai River at the 2nd Thai–Myanmar Friendship Bridge, all came in at 0.12. Even the Mekong River at Wiang Chiang Saen Municipality reached 0.14. Only a small creek near Thamphachhom-Hua Fai stayed within safe limits.

The worst contamination, 0.19 milligrams per litre, occurred at the Golden Triangle, where the Ruak flows into the Mekong at the meeting point of Thailand, Myanmar, and Laos. 

Polluted water from this key junction continues its course downstream through Cambodia and Vietnam, affecting millions who rely on the Mekong River for drinking water, agriculture, and fishing.

The research team has already sent the samples for further analysis at a certified lab, but the early results have triggered widespread concern. Since the Sai River begins in Myanmar’s Shan State and flows through active mining areas, experts suspect that runoff from metal and mineral extraction has tainted the water.

A separate report from northern Laos, released on 28 April, revealed similar problems in the Phark River in La District, Oudomxai Province. Residents there raised alarms after gold mining near the river’s headwaters appeared to affect water quality. 

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