The findings are based on four rounds of water sampling conducted on May 10, May 22, June 5, and June 24, 2026, at three monitoring locations: Luang Prabang, Bokeo C2—about 10 kilometres upstream of the Ruak River confluence with the Mekong River—and Houay Xay C5, approximately 32 kilometres downstream of the Kok River confluence.

The MRC said arsenic concentrations at all monitored sites remained below the 0.01 milligrams per litre (mg/L) standard specified in the Technical Guidelines on the Implementation of Procedures for Water Quality (TGWQ) throughout the monitoring period.

Water samples were analysed by the Biotechnology and Ecology Institute (BEI) under the Environmental Quality Analysis Centre of the Lao PDR using internationally recognised testing methods under its ISO/IEC 17025:2017-accredited quality management system.

MRC Secretariat Chief Executive Officer Busadee Santipitaks said the latest findings are encouraging but stressed the importance of continued monitoring.

"The latest findings are reassuring, but they should also remind us why regular monitoring is essential," she said. "Conditions in a large river system can change over time, and continued testing allows countries to detect trends early and respond in a timely manner with confidence."

The MRC said it will continue working closely with member countries and development partners to strengthen water quality monitoring, improve access to reliable scientific data, and support coordinated management of the Mekong River. The Secretariat added that updated monitoring results will continue to be released as they become available.

KPL