Research has sparked fear concerning the safety of salmon farmed in freshwater fisheries, with scientists uncovering worrying levels of potentially dangerous chemicals in some fish intended for human consumption. Harmful Polychlorinated Biphenyls (PCBs) are banned in many countries, but they find their way into the oceans as industrial waste, and from here contaminate fish whose offal is then manufactured into "nutritional" high-protein feed for the farmed salmon industry.