(Beyond Pesticides, May 22, 2007) In a study published in the latest issue of Environmental Toxicology and Chemistry, scientists found that seafood products from southern China contain high concentrations of DDT and hexachlorocylohexane (HCH). While banned in China since 1983, humans are being exposed to organochlorine pesticides (OCP) at rates high enough to pose health threats.
The study responded to high rates of DDT and HCH found in sediment, water and biota in the Pearl River delta and neighboring coast, where land is being rapidly industrialized, urbanized, and transferred from agriculture to commercial development.
Researchers tested 212 seafood products, including shrimp, crabs, and mollusks, from 11 coastal cities for 21 OCPs, including DDT, HCH, heptachlor, dieldrin, and endosulfan. The highest concentrations of DDT were found in four species of shellfish, although concentrations varied widely depending on sampling location.
The study reported, “These results suggest that bioaccumulation of DDTs in seafood products was highly species-specific, probably due to different feeding habits and habitats.” By taking a large sample of one indicator species, it also concluded “the coastal region of southern China is probably one of the most DDT-polluted areas in the world.”
Researchers also found HCH to be more widely prevalent than DDT, but in lower concentrations. The other OCPs were found to exist at relatively low levels, suggesting low potential for bioaccumulation and low residual levels in the environment.
The report’s conclusion is a warning sign for consumers. By the European Union’s maximum admissible concentration, 13.2% of the samples taken are considered to be over acceptable limits. The U.S. Environmental Protection Agency’s (EPA) comparatively strict guidelines show 32.1% of samples to exceed the allowable DDT residual level. Furthermore, if measured against the United Nations Food and Agriculture Organization’s estimated daily intakes (EDI), the EDI’s of both DDT and dieldrin are “higher than the cancer benchmark concentration . . . suggesting a perceptible health risk associated with consumption of seafood products.”
Such high concentrations of toxic pesticides have the potential to affect Americans as well as the Chinese, as a portion of China’s 3.2 million metric tons of exported seafood goes to the United States annually, passing through limited inspections.