Among six hairy crab samples — three collected at the import level and three from retail sales — Hong Kong’s Center for Food Safety recently found one with levels of dioxin and dioxin-like polychlorinated biphenyls or PCBs that exceeded the maximum allowed by law.

The finding promoted further review and caused Hong Kong to suspend import of any hairy crabs from the Jiangsu Providence after Nov. 1 “to ensure food safety.” Jiangsu is a coastal Chinese province north of Shanghai.

A medium-sized burrowing crab known for its furry claws, the Shanghai hairy crab is formally known as the Da Zha crab. Dioxin and dioxin-like PCBs are chemical compounds that accumulate in fatty tissues of animals along the food chain.

The contaminated sample was taken from the Shing Lung Hong Co., a retailer, who said an their hairy crabs came from an aquaculture farm on the Mainland.

“However, initial investigation by the CFS found that the concerned sample, when comparing against one of the two samples taken from the two aquaculture farms in Taihu where the import of hairy crabs to Hong Kong was suspended earlier, the proportions of the individual dioxins level of these two hairy crab samples were highly similar,” according to the CFS notice.

Taihu is a large lake located about one hour west of Shanghai on China’s Mainland, where there aren’t any maximum limits for dioxins or PCBs in food.

Because CFS had reasonable double that the suspect sample did not originate where the retailer claimed it did, the agency opened up a investigation and took other appropriate action, including the complicated analysis of dioxin and dioxin-like PCBs.

“The process includes extraction, multiple clean-up steps, instrumental analysis, substantial data analysis and review of findings when necessary, “ CFS’s spokeman said. “Thus, it normally takes two to four weeks for the analysis of dioxins and dioxin-like PCBs.”

Hong Kong requires that all food, locally produced or imported, must be fit for human consumption and each offense makes the violator subject to a $50,000 fine and/or six months imprisonment.

Dioxins and dioxin-like PCBs can cause cancers, reproductive and development problems, a weakened immune systems, They occur naturally in the environment and as by-products of industrial activities.

The CFS spokesman said: “Sources of human exposure to dioxins and dioxin-like PCBs include food intake, drinking water, air inhalation and skin contact. Dietary intake is by far the most exposure. Fatty foods, such as meat, poultry, seafood, milk and their products are the major dietary sources of dioxins and dioxin-like PCBs.”

For aquatic animals, CFS said parts like fatty livers and digestive glands are known to collect higher levels of dioxin and dioxin-like PCBs. Occasional short-term exposure, however, would not cause any health consequences.

The World Health Organization has established consumption limits based on body weight on a monthly basis. Its goal is to reduce exposures for girls and women to protect the developing fetus and breastfeeding infants.

China is not alone in not having established maximum limits for dioxins and dioxins-like PCBs. The international Codex Alimentarius Commission (Codex) has no maximums.

CFS is a unit of the Hong Kong Special Administrative Region. It conducted its first study into Dioxin and PCBs in 2011.

(To sign up for a free subscription to Food Safety News, click here.)