Toxicological evaluation of endosulfan in fish feed

1) Introduction To provide protection for food safety and animal welfare maximum limits for undesirable substances in animal feeds have been established by the European Union. The European Union has set considerably lower maximum limits for endosulfan (or ganochloride pesticide) in fish feeds compared to other animal feeds (0.005 versus 0.1 mg/kg). The particularly low maximum limits for endosulfan limits the development of novel aquafeeds based on terrestrial resources. The 20-fold difference in maximum l imits is partially based on the natural low level found in marine feed ingredients as well a high sensitivity of fish to waterborne endosulfan exposures. The route of uptake (water or diet) is of great importance to the toxic response for most xenobiotics . Data from feeding experiments are required in order to set appropriate maximum limits for endosulfan in aquaculture feeds. In general there is little knowledge on dietary toxicity of pesticides in fish. This account for A) Sublethal long-term toxic ef fects to fish (fish welfare) B) Carry over to parts of fish used for human consumption (food safety) Whereas aquatic endosulfan exposures rapidly lead to mortalities in fish, such acute toxicity has not been shown following feed exposures. For aquacultur e the sublethal adverse effects of endosulfan on general fish health during prolonged (life time) dietary exposures are of most importance. The use of early warning signals of toxic exposures (biomarkers) is an important tool when assessing threshold leve ls of dietary toxicity in experiments of relative short duration. The development of biomarkers as an early warning sign of toxicological effects will also reduce the need for experiments where a higher level of toxic agent needs to be used, hence need fo r experimental animals (fish).