Arsenic Alert in Kok River Prompts Cross-Border Pollution Probe

 

Mounting concerns over arsenic contamination in the Kok River have triggered an urgent response from the Thai government as testing reveals alarmingly high levels of the toxic substance.

 

Investigations conducted by the Water Management and Quality Control Office in Chiang Rai province identified excessive arsenic concentrations at multiple points during 2024 and 2025.

 

The contamination was first detected in the Kok River in July and September last year, with the Mekong River in Chiang Saen district also registering breaches in August and December 2024, continuing through to March this year.

 

Minister for Natural Resources and Environment Varawut Silpa-archa confirmed he had received instructions from Deputy Prime Minister Prasert Jantararuangtong to address the contamination as a matter of urgency.

 

"This situation presents significant environmental, public health and economic challenges for the region, particularly given the river's crucial role as a drinking water source,"Varawut said.
 

 

 

The Deputy Prime Minister has assembled a coordinated taskforce comprising 17 government bodies to tackle the crisis. Key responsibilities have been allocated as follows:

• The Ministry of Defence, Foreign Office and Office of National Water Resources will utilise diplomatic and military channels, including engagement through the Upper Mekong Water Group, to work with neighbouring countries on identifying and controlling pollution sources.

 

• The Ministry of Higher Education, Science, Research and Innovation has been directed to employ advanced satellite and geospatial technologies to trace the precise origins of the contamination.

 

• The Ministry of Interior will ensure safe drinking water supplies reach affected populations and coordinate public awareness campaigns.

 

• The Ministry of Agriculture and Cooperatives is conducting thorough checks for contamination in fish and aquatic life, while the Ministry of Public Health monitors for potential accumulation of arsenic within local residents.

 

• The Ministry for Natural Resources and Environment continues to oversee monitoring and inspection operations across the Kok River basin, with 14 monitoring stations measuring water levels, flow rates, sediment and rainfall.
   

 

 

Water quality analysis from April 2025 indicated that arsenic contamination was confined to the Mae Kok River itself, with no contamination detected in tributary streams.

 

The Pollution Control Department has doubled its testing frequency to twice monthly to ensure rigorous surveillance.

 

Meanwhile, the Department of Water Resources is implementing controls on sluice gates and preparing machinery to prevent contaminated water from reaching clean tributaries.

 

Diplomatic efforts are underway to engage neighbouring countries in finding a resolution, with the Ministry for Natural Resources and Environment working alongside the Department of Military Border Affairs to obtain environmental quality data and satellite imagery from the Geo-Informatics and Space Technology Development Agency (GISTDA).

 

Meanwhile, officials have moved to reassure the public that tap water remains safe for consumption in Chiang Mai and Chiang Rai provinces.

 

Tests conducted by the Provincial Waterworks Authority and the Department of Health have confirmed this safety, supported by urine samples from local residents showing no traces of contamination.

 

 

In a further development, the National Environment Board resolved on 6th May to establish a dedicated subcommittee focused on tackling surface water quality deterioration.

 

The 29-member committee, chaired by Deputy Prime Minister Prasert Jantararuangtong, will analyse the current situation and formulate solutions, including international negotiations to address pollution originating beyond Thailand's borders.