Birds and Insecticides

Birds and Insecticides

868 lead estimations at Great Ormond Street was the increased frequency of diagnosis after the introduction of the method. No doubt an increase in aw...

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lead estimations at Great Ormond Street was the increased frequency of diagnosis after the introduction of the method. No doubt an increase in awareness of the possibility of the diagnosis in atypical cases was in

part responsible. But easy

access to a test


only single specimen of blood was also a factor. The provision of similar facilities in other centres and the encouragement to use them would doubtless pay similar dividends, even though the aetiological and therapeutic implications of borderline blood-lead levels might be matters for debate. a

Birds and Insecticides THE decision1 of the Minister of Agriculture, Fisheries, and Food to restrict the sale of aldrin and dieldrin, the chlorinated hydrocarbon insecticides, after this year is not likely to be the end of this story. As might be the further the inquiry into the poisonous effects of these compounds is pursued the more complicated the problem appears. The first effects to be noted were deaths in seed-eating birds which had fed on seed corn which had been dressed with one of these substances as an insecticide. The victims were mostly game birds and wood pigeons (and if the slaughter had been limited to the pigeons these poisons would probably have received a subsidy). It soon became clear, however, that the carnivorous birds and mammals which feasted on these corpses also suffered. Most of these substances are very stable and how far this train of damage may run no-one yet knows. A second serious effect is the infertility of the eggs laid by birds which have had a sublethal dose, and this may cause greater changes in the bird population than direct or indirect


poisoning. A recent paper2 from the staff of the Nature Conservancy reports some more observations on the residue of insecticides in the flesh of 85 birds of many species which have been found dead without obvious evidence of acute poisoning. Herons showed 13 parts per million, grebes nearly 6 p.p.m., sparrowhawks nearly 4 p.p.m., and owls (of three species) from 1 to 2 p.p.m. Vegetarians, such as wood pigeons and moorhens, contained hardly any insecticides. The analysis of eggs showed a similar picture. The highest figures were in fish eaters and peregrine falcons, with golden eagles some way behind. The figures for carrion crows were much lower. We should like to see these figures set out at greater length. The range of values for 12 eggs of peregrine falcons from an unstated number of nests was 3.0-36,0 p.m., which will prove more to the naturelover than to the statistician. There are several possible explanations of these interspecies differences. It has been shown that hens concentrate dieldrin from their food about twenty times as effectively as do fat lambs.3 It is unlikely but not impossible that there should be metabolic differences of this order between birds. Fish are susceptible to amounts of dicophane (D.D.T.) which do little harm to 1. See Lancet, April 4, 1964, p. 758. 2. Moore, N. W., Walker, C. H. Nature, Lond. 1964, 201, 1072. 3. Gannon, N., Link, R. P., Decker, G. C. J. Agric. Food Chem. 1959,

other creatures, and this may be due to an unusual capacity for concentrating the substance from waterwhich might explain the high figures in herons and grebes. Has anyone examined frogs which make up a good part of the diet of both ? One difficulty in coming to firm conclusions from this sort of evidence is our ignorance of the diet of many birds at different seasons: what is their bread-and-butter and what their caviare? Discussing the acute toxic effects of these poisons, we have more than once pointed to the absence of anything like controlled observations. Birds found dead from unknown causes may not be the best material for analysis. Indeed, we suspect that observation has probably told us as much as it can for the time being and the time is ripe for experiments. The difficulties are considerable, but work done in the U.S.A.4 (on species most of which are unknown here) has gone some way to establish the toxic dose of some of these compounds, As prosecuting counsel has often found, the mere presence of a poison in the human body is not enough to bring anyone to the gallows. The decision to restrict the sale of aldrin and dieldrin is justified until we know rather more than we do now, but we would not care to accept all the forecasts of future woe. Growing cabbages and carrots is a hard way of earning a living-and without an insecticide at least as good as aldrin and dieldrin it is going to be harder still.


A UNIVERSITY which appointed its first professor of medicine in 1685 is not likely to produce a revolutionary The changes announced at new medical curriculum. Edinburgh, although essentially conservative, are interesting in that they do show adaptation to recent trends that are becoming established. First, the time given to anatomy has been axed from 900 to 500 hours. This is an uneasy compromise. There are still, especially at the old who view this reduction traditionalists Edinburgh, with alarm, but most younger teachers probably consider 500 hours still far too long. Secondly, there is an inducement for the medical student to broaden his education by taking classes outside the medical faculty. This has arisen because of the realisation-after long students enter the university with very different scientific educations. Until recently all have had to take a common first-year course in chemistry, physics, and biology. Students with the appropriate school certificates will now be exempted from this course and can qualify in 5 years. Students with qualifications in one or two subjects only, which will include a large number of entrants from Scottish schools, where the teaching of biology is in general inadequate, will be partially exempt. In their first year, when not engaged in their remaining science subjects, they will be enabled to take courses in subjects such as psychology, social anthropology, and mathematics. Incentive for this will be the award of a (Med. Sci.) after three years’ satisfactory study in the medical faculty. It remains



7, 826.

Bernard, R. F. Publications of the Museum, Michigan State University (Biological Science), 1963, vol. 2, p. 155.