Picture courtesy of The Standard 

 

The Pollution Control Department (PCD), under the Ministry of Natural Resources and Environment, has raised the alarm over elevated arsenic levels found in several major rivers in the northern provinces of Chiang Rai and Chiang Mai.

 

According to the seventh round of water and sediment quality assessments conducted between 30 June and 4 July 2025, arsenic concentrations exceeding national safety standards were detected in the Kok, Sai, Ruak, and Mekong rivers, particularly in areas close to the Thai-Myanmar border.

 

River Kok: Widespread Contamination

 

All 15 monitoring sites along the Kok River (labelled KK01–KK15), stretching from Mae Ai District in Chiang Mai to Ban Saeo in Chiang Saen District, Chiang Rai, reported arsenic levels surpassing the national threshold of 0.010 milligrams per litre (mg/L). The highest concentrations were recorded at KK01 near the Thai-Myanmar border in Tha Ton, Mae Ai (0.016 mg/L), and KK02 at the Nawng Friendship Bridge (0.015 mg/L).

 

In contrast, tributaries feeding into the Kok, including the Fang River (FA01), Korn River (KO01), Suai River (SU01), and Lao River (LA01), were found to meet national water quality standards.

 

River Sai: Sharp Spikes at Border Crossings

 

In the Sai River, all three monitored sites exceeded safe limits. Notably, SA02, at the second Sai River Friendship Bridge in Mae Sai, Chiang Rai, showed arsenic levels as high as 0.049 mg/L. Other points, such as SA01 in Ban Hua Fai and SA03 in Ban Pa Sang Ngam, also reported elevated levels of 0.023 and 0.024 mg/L respectively.

 

River Ruak: One Site Over the Limit

 

Of the two monitored points on the Ruak River, only RU01, at the Provincial Waterworks Authority’s pumping station in Koh Chang, Mae Sai, exceeded the limit, registering exactly 0.010 mg/L. RU02, near the river’s confluence with the Mekong, remained within acceptable levels.

 

Mekong River: All Sites Affected

 

All three sampling sites along the Mekong in Chiang Saen District, Chiang Rai, showed arsenic concentrations above the safety standard. NK01 at the Golden Triangle permanent border checkpoint registered 0.011 mg/L, while NK02 in Wiang subdistrict recorded 0.012 mg/L. NK03 at Ban Sob Kok reported 0.011 mg/L.

 

Ongoing Environmental Monitoring Planned

 

In response, the PCD has announced an intensified environmental monitoring programme for the rest of the 2025 fiscal year. Water samples will be collected twice a month from July to September, and sediment samples will be gathered monthly. The initiative aims to closely monitor the ongoing risk and protect public health and aquatic ecosystems in northern Thailand.

 

Authorities have urged local residents and relevant agencies to remain vigilant and support measures to identify the sources of contamination and mitigate its impacts.

 

 

  Adapted by Asean Now from The Standard 2025-07-27

 

 

 

 

 

 

Keep doing what you're doing Thailand. It’s working.

3 hours ago, Georgealbert said:

 

Picture courtesy of The Standard 

 

The Pollution Control Department (PCD), under the Ministry of Natural Resources and Environment, has raised the alarm over elevated arsenic levels found in several major rivers in the northern provinces of Chiang Rai and Chiang Mai.

 

According to the seventh round of water and sediment quality assessments conducted between 30 June and 4 July 2025, arsenic concentrations exceeding national safety standards were detected in the Kok, Sai, Ruak, and Mekong rivers, particularly in areas close to the Thai-Myanmar border.

 

River Kok: Widespread Contamination

 

All 15 monitoring sites along the Kok River (labelled KK01–KK15), stretching from Mae Ai District in Chiang Mai to Ban Saeo in Chiang Saen District, Chiang Rai, reported arsenic levels surpassing the national threshold of 0.010 milligrams per litre (mg/L). The highest concentrations were recorded at KK01 near the Thai-Myanmar border in Tha Ton, Mae Ai (0.016 mg/L), and KK02 at the Nawng Friendship Bridge (0.015 mg/L).

 

In contrast, tributaries feeding into the Kok, including the Fang River (FA01), Korn River (KO01), Suai River (SU01), and Lao River (LA01), were found to meet national water quality standards.

 

River Sai: Sharp Spikes at Border Crossings

 

In the Sai River, all three monitored sites exceeded safe limits. Notably, SA02, at the second Sai River Friendship Bridge in Mae Sai, Chiang Rai, showed arsenic levels as high as 0.049 mg/L. Other points, such as SA01 in Ban Hua Fai and SA03 in Ban Pa Sang Ngam, also reported elevated levels of 0.023 and 0.024 mg/L respectively.

 

River Ruak: One Site Over the Limit

 

Of the two monitored points on the Ruak River, only RU01, at the Provincial Waterworks Authority’s pumping station in Koh Chang, Mae Sai, exceeded the limit, registering exactly 0.010 mg/L. RU02, near the river’s confluence with the Mekong, remained within acceptable levels.

 

Mekong River: All Sites Affected

 

All three sampling sites along the Mekong in Chiang Saen District, Chiang Rai, showed arsenic concentrations above the safety standard. NK01 at the Golden Triangle permanent border checkpoint registered 0.011 mg/L, while NK02 in Wiang subdistrict recorded 0.012 mg/L. NK03 at Ban Sob Kok reported 0.011 mg/L.

 

Ongoing Environmental Monitoring Planned

 

In response, the PCD has announced an intensified environmental monitoring programme for the rest of the 2025 fiscal year. Water samples will be collected twice a month from July to September, and sediment samples will be gathered monthly. The initiative aims to closely monitor the ongoing risk and protect public health and aquatic ecosystems in northern Thailand.

 

Authorities have urged local residents and relevant agencies to remain vigilant and support measures to identify the sources of contamination and mitigate its impacts.

 

 

  Adapted by Asean Now from The Standard 2025-07-27

 

 

 

 

 

 

Water testing twice a year seems weak and would not help anyone should the levels increase. Thailand should be doing tests on the water monthly to assess any increases in toxicity. At the very least they should test the waters quarterly. 

...release all water quality test results for town water supplies drawn from these toxic rivers.