CHIANG RAI –Toxic heavy metals from mining activities in a neighboring country are contaminating local rivers, threatening more than 60,000 rai (around 24,000 acres) of crucial farmland in the Mae Sai district.
Farmers in the area are sounding the alarm over dangerous levels of arsenic, lead, and cadmium seeping into their soil and crops. Local leaders are urging the Ministry of Agriculture and Cooperatives to step in immediately before the silent crisis destroys the region’s economy and food safety.
According to a report by the prominent Thai news outlet Khaosod Online , the contamination affects five major sub-districts that rely heavily on the Sai and Ruak rivers. The toxic chemicals travel downstream, carried by water and mud into local irrigation systems. This water feeds crops that local families eat and sell to domestic and international markets.
Farmers Propose Three-Step Plan to Save Local Crops
On May 25, 2025, Thongkham Inprom, the chairman of the Ban Mueang Chum Water Users Group, hand-delivered a formal complaint to Piyarat Tiyapairat, the Deputy Minister of Agriculture and Cooperatives. The meeting took place while the minister was inspecting the RC1 irrigation canal office in Mae Sai.
Local farmers are asking the government to focus on three urgent solutions:
- Provide Solar-Powered Groundwater:Install solar-powered water wells directly on individual farms so growers do not have to rely on tainted river water.
- Build the Mae Kham Reservoir:Speed up the construction of the planned Mae Kham Reservoir in the Mae Fah Luang district to supply clean, alternative water to the region.
- Launch International Talks:Coordinate with neighboring countries to halt upstream mining operations and stop the dumping of industrial waste into shared rivers.
More Than 60,000 Rai of Essential Food Crops at Risk
The pollution threatens five highly productive agricultural sub-districts in Mae Sai: Mae Sai, Sri Mueang Chum, Pong Pha, Wiang Phang Kham, and Koh Chang. Together, these areas span over 60,500 rai of farmland.
Farmers utilize the RC1, RC2, and RC3 irrigation canals to grow seasonal rice and major cash crops. The affected items include:
- Potatoes and sweet corn
- Garlic and shallots
- Animal feed corn
- Okra and soybeans
“Farmers are facing an immediate crisis with arsenic, lead, and cadmium,” Thongkham told reporters. “These poisons accumulate in the dirt and the food we grow. It is creating a massive wave of anxiety for both the farmers and the consumers who buy our produce.”
Thongkham noted that while the long-term health risks are incredibly dangerous, many local farmers still do not fully understand the threat. Because heavy metal poisoning is a “silent killer” that builds up over several years, getting the community to unite and demand change has been difficult. Furthermore, no single government agency has stepped up to take full responsibility for managing the polluted irrigation network.
The Struggle to Secure Clean Alternative Water Sources
Getting clean water to the five affected sub-districts will not be easy. The proposed Mae Kham Reservoir is physically located outside the service zone of these communities.
Despite the geographic challenges, Thongkham refuses to give up. He is actively meeting with upstream communities to pitch an alternative plan: building a connected pipeline network to pump clean water from the Mae Kham Reservoir directly into the RC1 irrigation canal.
“If a baby does not cry, nobody knows it wants milk,” Thongkham said, using a traditional northern proverb. “If we do not speak up about what we need, nobody will ever know. We have to keep fighting because the pollution is only getting worse.”
Scientists Discover High Contamination Levels Far From Riverbanks
During the minister’s visit, agricultural experts and scientists shared startling new data about the local soil. Scientists from the Land Development Department tested dirt samples within a two-kilometer radius of the main rivers.
Surprisingly, their research showed that soil located further away from the riverbanks often contained higher amounts of toxic metals than the soil right next to the water. Experts explained that this happens because heavy rains and floods carry toxic sediment deep into inland fields, where the mud settles and dries.
To combat this, the Land Development Department announced a safety initiative:
- Frequent Testing:Teams will test local soil samples two to three times every year to track toxic movements.
- Color-Coded Risk Maps:Authorities are building a mapping system that divides farmland into Green, Yellow, and Red safety zones.
- Crop Blockers:Deputy Minister Piyarat Tiyapairat has ordered scientists to find agricultural techniques that block plants from absorbing heavy metals through their roots, while search teams look for entirely new water sources.
