An independent food safety researcher has called on authorities in the Chinese mainland to impose tough limits on dioxin contamination of water and soil, following the detection of the carcinogen in Jiangsu hairy crabs sold in Hong Kong.
Hong Kong’s Centre for Food Safety said on Tuesday it found excessive dioxin levels in two of five hairy crab samples from two mainland farms it tested. One sample had 11.7 picograms of the contaminant per gram and the other 40.3 picograms, well above the safe level of 6.5 picograms.
A Jiangsu quarantine bureau official said the bureau had suspended export clearances for the two farms and a task force had been set up to test water and product samples, Xinhua reported.
Sun Xingliang, director of the Wanqing crab farm in Wujiang, one of the two involved, said the crabs exported by his company were all tested for pesticide residue and heavy metals, but not dioxins.
“It’s the first time that my company’s product has been accused of dioxin contamination in 16 years of exporting. I have no idea what a dioxin is,” Sun said.
Dioxins are a group of chemicals commonly formed as by-products of industrial combustion and chemical processes, such as manufacturing of chemicals, pesticides, steel and paints, and waste incineration.
They are fat-soluble and not easily broken down. They can accumulate in the human body through intake of animal derived food, and can cause cancer and damage the reproductive and immune systems.
Sun said the company’s crabs, farmed at Lake Tai, were also exported to Singapore, Taiwan, and Macau, and he was worried the Hong Kong findings could affect those markets as well.
He also said the mainland’s inspection and quarantine authorities had “intervened” and would organise testing.
Mao Da, a director of the Rock Environment and Energy Institute, an independent think tank, said the two mainland companies were also victims of polluters and lax monitoring.
“The mainland’s food safety standards do not refer to dioxin levels. So it is possible that hairy crabs sold on the mainland are also tainted with dioxin,” said Mao, who has done extensive research on dioxin pollution in China.
Mao said dioxins tended to accumulate in soil, or lake and river sediment, so it was not surprising that the contaminants were detected in crabs bred in Lake Tai, which is located in a highly industrialised area.
A study conducted by Mao’s organisation earlier this year found dangerous levels of dioxins – by European standards –in free-range chicken eggs produced close to waste incinerators and other industrial hot spots in six mainland areas, including Shenzhen, Beijing and Wuhan.
In February, Nature-affiliated magazine Scientific Reports published a study led by Lanzhou University Professor Ma Jianmin that found people on the mainland were facing a growing risk of cancer from dioxins due to changes in dietary patterns and rising emissions. The risk rose from 0.2 per cent in 1980 to 1.2 per cent in 2009, the study found.
Public awareness of the health effects of dioxins has triggered protests against waste incinerator projects on the mainland, but environmental authorities have failed to set safety limits for the contaminant.