China, the largest producer and exporter of fish and fish products in the world, is likely to come under pressure to more closely monitor shellfish contaminant levels after a study in Environmental Toxicology and Chemistry found worryingly high levels of organochlorine pesticides in oysters, mussels, and squid. The report says that samples from fish markets in Guangdong Province contained concentrations of contaminants high enough to pose a threat to human health. Although organochlorine pesticides were officially banned in 1983, China had been using them for decades prior to the ban. Because organochlorines do not degrade easily, they can remain in the environment for years, moving up and down the food chain. Additionally, there is evidence that new sources, particularly of DDT, may be present and contributing to the contamination.
The new study focused on seafood from markets in 11 coastal cities in Guangdong Province, an area that has experienced explosive economic growth in recent years. Rapid industrialization, urbanization, and conversion of agricultural lands to commercial use have accelerated the environmental deterioration in this region, say the researchers.
The researchers analyzed shrimps, crabs, and mollusks for 21 different organochlorine pesticides. They reported that DDT and HCH (hexachlorocyclohexane) were detected most frequently and measured at the highest concentrations. These highest concentrations were observed in mollusks - specifically oysters, mussels, and squid. Concentrations of DDT in some of the seafood were high enough to pose human health threats. Other organochlorine pesticides present were at concentrations high enough to pose human cancer risks.
China currently exports more than 3 million (metric) tons of seafood products per year, primarily to Japan, Korea, the United States and Europe. The report's authors urge that further research be conducted to identify the new sources of organochlorine pesticide contamination and to ascertain whether consumer advisories be issued in relation to consumption levels.
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Source: Environmental Toxicology and Chemistry
