【英语时差8,16】人工养殖三文鱼可能含有更多化学成分（在线收听）

The study tested uncooked salmon with the skin left on. Health officials say most pollutants are in the skin and the fat just below. They say removing the skin and cooking away fat removes many of the pollutants. The study says the chemicals apparently entered the farm-raised salmon through the fish products they were fed. Salmon in the wild eat small fish and sea organisms that contain fewer P-C-B's and other chemicals. The salmon industry notes that meat and milk products can also contain P-C-B's. But it says salmon farmers are reducing the levels in their food by using, for example, soybean oil in place of fish oil. P-C-B's were used to make products like plastics and paint. The United States banned this group of chemicals in the nineteen-seventies. But they remain in the environment. Another chemical, dioxin, is released when plastics and some other materials are burned. Dioxin has been linked to reproductive and developmental problems in addition to cancer. People do not always know if the salmon they eat was farmed or wild or where it came from. The study calls for stores and eating places to provide more information.