It is certainly correct that many of Carson's claims about the environmental effects of DDT cannot be substantiated. Carson, who had trained as a biologist but made a career as a nature journalist, was interested in raising public awareness of the deterioration of the environment through industrial products, at a time when such ideas were novel and went against the general belief in scientific progress at all cost. She was successful to such a degree that her book is now widely considered to mark the beginning of the environmental movement. That she argued her case with wild exaggerations and several wrong claims may be understandable for someone who can see the future of a world with an unrestrained chemical industry but is met with hostility wherever she goes, but that does not exonerate her from having employed dishonest means.
Edwards' claim of scientific fraud is another matter. As Edwards reports himself, the DDT hearing of the EPA, which lasted seven months, came to the conclusion that DDT does not pose a threat to human or animal health and recommended to allow its use as a pesticide; but the recommendation was overruled by the EPA Administrator, who had links with an environmental group. There was thus no scientific fraud: Science came to the correct conclusion. The fault lay with the administration, i.e. in the political domain.
Edwards' paper is not completely free from misleading claims. It focuses on DDT use for mosquito control in malaria eradication, describes the early successes with DDT spraying between 1945 and 1960 and says: "After the U.S. ban on DDT, there is a global malaria burden of 300 to 500 million cases and 1 to 2.5 million deaths annually, mostly among young children. Malaria kills an African child every 30 seconds." As Edwards describes it, the ban on DDT can only be seen as a crime against humanity.
This picture is far from the truth for several reasons:
- The use of DDT for malaria control represented a very small proportion of general DDT use of the 1950s and 1960s. Widespread use of DDT in agriculture, while possibly of no harm to humans, can only increase resistance to it and is therefore only a temporary gain, while the quantity of DDT in the environment accumulates. DDT is very persistent in the environment, and the low doses recommended by the EPA science assessment may eventually be exceeded by large amounts.
- The ban on DDT refers only to agricultural use; its use in malaria control has always been permitted. The World Health Organization recommends DDT for indoor spraying, a use that was formally included in the Stockholm Convention on Persistent Organic Pollutants in May 2004, 6 months before Edwards' paper was published. (Indoor spraying – the coverage of walls and ceilings with a thin DDT layer - prevents mosquitoes entering buildings but does not kill them; it acts as a barrier between mosquitoes and humans.)
- The claim that continued use of DDT would have saved millions of lives cannot be verified. Many mosquito populations have developed resistance to DDT (in Sri Lanka, India and many other countries as early as 10 years before DDT was banned). Effective malaria control now requires the use of alternatives such as pyrethroids (synthetic chemical compounds that emulate the natural chemical pyrethrins produced by certain Chrysanthemum flowers and are used in many insect repellents). Ironically, the rapid loss of effectiveness in the 1960s was mainly the result of agricultural DDT spraying, which used much larger quantities than malaria control. This suggests that DDT effectiveness for malaria control could have been maintained much longer if agricultural use of DDT would have been banned 20 years earlier.
Carson R. (1962): Silent Spring. Houghton Mifflin, Boston, Mass.
Edwards, J. G. (2004): DDT: a case study in scientific fraud. Journal of American Physicians and Surgeons 9 (3), 83-88; available as PDF file.
World Health Organization (2004): WHO position on DDT use in disease vector control under the Stockholm Convention on Persistent Organic Pollutants. WHO/HTM/RBM/2004.53 rev.1, available as PDF file
More information and debate at http://timlambert.org/category/science/ddt