According to a paper published in Science on January 9th, levels of organochlorines in farmed salmon are so high in Scottish output that people should eat less than half a portion of salmon a month. Organochlorines are unpleasant chemicals such as dioxins and PCBs (polychlorinated biphenyls) produced by industry that hang around in the environment. They accumulate in animals, concentrating in the fatty parts. The authors of the Science paper looked at 700 salmon from around the world. Europe's salmon came off worst overall; among European salmon, Scottish fish did particularly badly. Yet America's Food and Drug Administration (FDA) and Britain's Food Standards Agency (FSA) think there is nothing to worry about, so long as people eat the amounts they recommend. Contaminant levels reported in the study are easily within guidelines set by the FDA, the World Health Organisation and the European Commission. So why did the authors of the Science paper come to such a different conclusion? Because they based their findings on the method of assessing toxicological risk used by a different regulator, the Environmental Protection Agency(EPA), to advise sport fishermen how much of the fish they catch they can eat.