The persistent organic pesticides have saved millions of lives by controlling human disease vectors and by greatly increasing the yields of agricultural crops. However, in recent years man has become ever more conscious of the way in which his environment is becoming increasingly polluted by chemicals that may harm plants, animals or even himself. Amongst these chemicals the organochlorine insecticides have been well to the fore as a major cause of anxiety to ecologists, not only because they persist so long, but also because of the readiness with which they are taken up into the bodies of...