Environmental experts on Friday warned the slick of cancer-causing benzene moving along China’s Songhua river could pose a long-term risk to human health, contaminate the food chain and damage the region’s fragile ecosystem.
As the 80km-long highly toxic column moved into Harbin, capital of the northeastern province of Heilongjiang, analysts said dangers would remain for years.
Kenneth Leung, an eco-toxicologist from the University of Hong Kong, said benzene would settle in the river sediment and be taken into the food chain by tiny fish which scour the river bed for food.
”Those higher up in the food chain such as water birds and humans could suffer,” Leung said, explaining that animals can easily accumulate benzene but they are unable to metabolise, or dispose of, the chemical.
”Benzene can bond to DNA and cause mutation which can lead to cancer,” he said.
Mains water has been turned off in Harbin until the slick flows further downstream, but Leung said that without data he could not predict when it would be safe to drink again.
”It needs regular monitoring and that is what they are doing now,” Leung said.
His colleague, marine pollution expert Gu Jidong, whose hometown is in Heilongjiang downriver from Harbin, said the pollution could pose a danger for several years after the slick had passed.
”With these classes of chemicals some of the micro-organisms can be degraded but some cannot. The chemicals they have released are very soluble so the river will be carrying them downstream,” Gu said.
With the onset of winter and the imminent freezing over of the Songhua river, the biological breakdown of the chemicals by sunshine or microbes would be slowed, Leung said.
Harbin, highly dependent on the 1 897km Songhua for its water supplies, has about 3,8-million urban residents and a total population of about nine million.
It was still unclear on Thursday how the environmental disaster had affected Songyuan and Zhaoyuan, two other major cities between Harbin and Jilin that also depend on the Songhua for water.
”If people are close to the spill that is a very dangerous place to live,” said Gu.
”The chemical will stay in the sediment and some will evaporate into the air. When people are breathing they will inhale it and it will have a long-term impact.”
Chinese officials have said 100 tonnes of benzene and benzene derivatives were released into the river after a massive explosion at a PetroChina chemical plant in Jilin province on November 13.
Subsequent toxicity in the Songhua river had exceeded national safety levels by more than 100 times near the blast site.
Benzene is a colourless solvent widely used in plastics, dyes, detergents, insecticides. But it is also a carcinogen that can be lethal to humans, even in small doses.
According to the United States Environmental Protection Agency, a short period of exposure to benzene can cause temporary nervous system disorders, immune system depression and anemia.
Long-term chronic exposure can lead to degeneration of bone marrow and leukemia, as well affecting the reproductive system.
Environmental group WWF, which has been working on forest conservation and species protection in the area close to the explosion since 2001, expressed concern for the region’s ecosystem.
”WWF is highly concerned about how the toxic spill in Heilongjiang province will impact on the region’s people and ecosystem,” said Li Lifeng, director of WWF China’s freshwater programme.
He said the province was home to one of the world’s most distinctive temperate forests which are the habitat of many endangered animals, plants and bird species, including Siberian tigers, leopards, brown bears, Asiatic black bears, yew trees and red-crowned cranes.
Environmental group Greenpeace urged authorities to protect people in the affected areas.
”It should for example conduct a comprehensive environmental impact assessment of the pollution and, on that basis, draw up and implement an effective clean-up plan,” Kevin May, the toxics campaign manager of Greenpeace China, said in a statement.
Zhang Lijun, vice head of the State Environmental Protection Administration, on Wednesday pledged to monitor chemical levels long after the pollution had been cleaned up. – AFP
