Correspondents' Correspondence

...Correspondents' Correspondence BRIEF TAKEOUTS OF MORE THAN PERSONAL INTEREST FROM LETTERS AND OTHER COMMUNICATIONS RECEIVED BY THE EDITORS Pesticide Breakthrough London—A deadly substance derived from an East African flower has given scientists here the basic molecular blueprint for a highly active pesticide And this discovery—at the Roth-amsted experimental station of the United Kingdom Agricultural Research Council—may well provide one of the essential answers to the question of survival that is sure to face mankind in the coming decades of population explosion and mounting food demand The new synthetic compounds, called resmethrin and bioresmethrin, are related to pyrethrin, a costly natural pesticide They are inexpensive, pollution-free and 100 times more effective than DDT Britain's National Research Development Council thinks them so important, in fact, that it has established patent protection over them Dr Michael Elliott and Dr Norman Janes, the (wo men chiefly responsible for the breakthrough, also have received a joint award of approximately $40,000 to be paid by the Council out of income from the commercial manufacture of the compounds—income that should be substantial, considering the need that exists for such a product Insects destroy around a third of the earth's total food yield, despite considerable recent improvements in combating them, and millions of people still die yearly from insect-transmitted diseases Since the introduction of DDT after World War II for the control of agricultural pests and disease vectors, resistance to that chemical and other insecticides has developed in no less than 110 species of public health importance Thus malaria has reappeared in many regions once free of it, and the vectors—anopheline mosquitoes—have shown resistance to all the pesticides tried on them This sort of situation often requires the replacement of safer and cheaper chemicals with something more expensive and toxic—involving the added expenditure of special safety measures during use Their effect on the environment, moreover, is cumulative and irreversible for generations Hence the importance of the just-developed compounds A spokesman for the research team explains that the natural pyrethrins, available since the 1920s, "also act rapidly against a wide range of insect species, are harmless to mammals in normal use and leave no toxic residue to contaminate the environment Unfortunately, they have a limited applicability because they are unstable in air and light and rather expensive " He noted, too, that "workers at the experimental station here synthesized two similar compounds over a decade ago These were more effective and even less dangerous to mammals than the natural pyrethnns, attaining the greatest safety margin of any known insecticide However, like the natural compounds, both proved unstable in air and light, making them unsuitable for agriculture and widespread public health projects " The new chemicals have none of the problems and all the advantages of their predecessors Exposed to air and light, their molecular structure eventually breaks down—thereby averting environmental pollution, although their stability is about 100 times that of the earlier pyrethroids They are much more powerful but have the same low level of mammalian toxicity They are also easier to produce in a laboratory or to mass produce in a factory, and so are likely to be much cheaper than the high-power pesticides currently available The relatively low production costs of the resmethnn and bioresmethnn will eventually put the new discovery within the reach of the developing countries of Asia, Africa and Latin America These are the very nations where the pesticides are most urgently needed in food production, storage and public health schemes—and where the least foreign exchange reserves are available for expensive imports —thomas land...