Toxic Leak in Hunan Traced to a Former Cement Plant

A botched demolition at a cement plant in central China’s Hunan province has been identified as the source of a toxic leak that contaminated a major river in mid-March, according to the results of an official investigation.

On March 16, the government of Hunan’s Yongxing County issued a notice stating that a surface water station on the Leishui River had detected abnormal concentrations of thallium, a toxic heavy metal.

The Hunan Provincial Department of Ecology and Environment announced Monday that thallium concentrations — which had reached as high as 0.13 micrograms per liter in some parts of the Leishui River, well in excess of the national surface water standard of 0.1 micrograms per liter — had returned to safe levels along the river’s entire course.

Thallium salts are colorless, tasteless, and highly soluble in water. The estimated lethal dose for an adult is approximately 10 to 15 milligrams per kilogram of body weight, meaning less than 1 gram can be fatal.

The affected river, the Leishui, is the largest tributary of the Xiang River, which runs into the Yangtze River. It stretches 446 kilometers, covering a watershed of 11,770 square kilometers and flowing through eight county-level regions.

The primary section of the Leishui set aside for drinking water is located approximately 35 kilometers downstream from where the abnormal thallium concentrations were detected.

Local authorities identified a nearby cement plant as the source of the leak as early as March 17, determining that dust from a recently demolished kiln had been washed into the river by rainfall. The runoff entered the surrounding environment through a stormwater discharge outlet, contaminating the nearby waters.

State broadcaster CCTV reported that the cement plant in question began dismantling its production line at the end of last year, leading to a significant release of thallium-laden dust.

“The kilns contained accumulated thallium-rich dust, which, when dispersed onto the ground, could reach concentrations of several thousand milligrams per kilogram,” Huang Rongxin, an expert with China’s Ministry of Ecology and Environment, told the state broadcaster.

The source came as a surprise, experts say, as thallium contamination is generally linked with mining and smelting operations, rather than cement.

“Typically, cement plants do not contain significant levels of thallium in their raw materials — certainly not enough to cause environmental contamination,” Peng Yingdeng, a researcher at the Ministry of Ecology and Environment’s Industrial Wastewater Pollution Control Engineering Technology Center, told domestic media.

According to Peng, the nearby city of Chenzhou is a hub for non-ferrous metal mining and processing, and a number of cement plants in China have been repurposed to process industrial solid waste in recent years.

“This method is considered an emerging approach for hazardous waste disposal, but it can lead to high concentrations of thallium salts in kiln residue,” Peng was quoted as saying.

It is not clear whether the cement plant in question ever processed industrial waste, but according to an industry database, the plant’s owner, Hunan Liangtian Cement, added solid waste management to its list of businesses last September.

Domestic media reported that at least six cement production enterprises in Chenzhou are engaged in the utilization of industrial solid waste.

In late March, when the full extent of the contamination’s impact was unclear, Liu Hongjun, the Party secretary of nearby Dahetan Village, told business news outlet Caixin that villagers had been instructed not to fish or enter the water as a precaution.

The Hunan provincial government has dispatched teams to apply chemical treatments to the affected areas. “They are still working on it, but water quality in our section has basically returned to safe levels,” Liu said.

He also noted that Dahetan Village relies on groundwater rather than Leishui River for daily use, meaning local residents’ drinking water was not affected.

According to the official report by the Hunan Provincial Department of Ecology and Environment, thallium concentrations in water supply facilities downstream have remained within the national drinking water safety standard of 0.1 micrograms per liter since March 16.

Hunan has dealt with multiple thallium contamination incidents in recent years, with abnormal concentrations detected in 17 out of 22 drinking water sources along the Xiang’s main course. In August 2020 alone, 12 water sources recorded elevated thallium levels.

Hunan authorities launched a special remediation campaign in 2021, but the latest incident has raised awareness of potentially overlooked risk factors, local regulators say.

“In the past, environmental regulators mainly focused on monitoring production activities, often overlooking the environmental risks associated with non-operational conditions,” Wang Shengcai, deputy director of the Hunan Provincial Department of Ecology and Environment told CCTV.

“This incident serves as a wake-up call, highlighting the need for experts to assess and detect potential risks before taking action,” he added. “Proper plans should be in place to prevent environmental pollution.”

(Header image: Onuma Inthapong/Getty Creative/VCG)