CHIANG RAI – Residents and tourists in Northern Thailand are being urged to exercise extreme caution when consuming aquatic life from local rivers. The Pollution Control Department (PCD) has issued a formal warning following the discovery of dangerous levels of arsenic in the sediment of several major rivers, including the Kok and Mekong.
The alert comes after the 10th consecutive round of water and sediment quality testing conducted by environmental officials. The results indicate a worrying shift in the safety of the riverbeds, posing a direct threat to both the ecosystem and public health.
According to Mr. Surin Worakitchamrong, Director-General of the Pollution Control Department, the latest monitoring cycle revealed that arsenic levels in several key locations have reached “unsafe” and, in some cases, “severely hazardous” levels for bottom-dwelling organisms.
The affected areas identified in the report include:
- Tha Ton, Mae Ai District (Chiang Mai): Specifically near the Mae Na Wang-Tha Ton Friendship Bridge.
- Mueang District (Chiang Rai): Levels were spiked at the Chaloem Phra Kiat Bridge in the Rob Wiang sub-district.
- The Mekong River: Abnormal readings were detected at every monitoring station along this international waterway.
Environmental experts point to the current dry season as the primary driver of this toxic buildup. With water levels at an annual low, the river flow has slowed significantly. This “sluggish” movement allows suspended particles and heavy metals to settle and accumulate on the riverbed rather than being washed downstream.
As these toxins concentrate in the mud, they enter the food chain through “bottom feeders”—fish, snails, and shellfish that live and feed on the river floor.
Health Recommendations for Residents
While the water itself may appear clear, the danger lies beneath the surface. To ensure public safety, the PCD has released the following guidelines for residents in Chiang Mai and Chiang Rai:
- Avoid Bottom-Dwelling Species: Refrain from catching or eating aquatic animals that live in the sediment, such as certain types of catfish, shellfish, and snails from the affected zones.
- Monitor Water Usage: While primarily a sediment issue, those using river water for agriculture or personal use should stay updated on local quality reports.
- Prioritize Sourced Seafood: When purchasing fish in local markets, inquire about the source to ensure the catch did not originate from the high-risk areas of the Kok or Mekong rivers.
Arsenic is a naturally occurring element, but its concentration can be exacerbated by human activities such as mining and industrial runoff. When levels reach the “severe” threshold, it can lead to mass die-offs of aquatic species and long-term soil contamination.
The Pollution Control Department has committed to ongoing monitoring and will provide updates as weather patterns shift and water volumes hopefully increase with the coming rains. For now, the message remains clear: caution is the best defense against this invisible threat.
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