§ Mr. Hardyasked the Minister of Agriculture, Fisheries and Food what assessments have been made of the lethal and sub-lethal effects on British wildlife of the DDT derivative DDE.
§ Mr. Peter WalkerThis has been the subject of extensive laboratory and field studies by staffs of my Department, the Nature Conservancy Council and the National Environmental Research Council. These studies, which are continuing, have related mainly to birds, but there has also been some work on mammals, fish and amphibians. The studies have shown that in dead birds residue levels of 150 parts per million in the liver and 50 parts per million in the muscle are indicative of death due to organochlorine poisoning by DDE. The most obvious sub-lethal effect in birds is eggshell thinning.
Sub-lethal doses of DDE have also led to changes in behaviour in wildlife, such as birds and amphibians. Any effect on freshwater life tends to be confined to the area of insecticide treatment, whereas on birds it is more widespread.