DDT and Chemophobia - Could DDT help with the West Nile Virus outbreak?

This week marks the thirtieth anniversary of the unfortunate ban on DDT, and politicians are poised to make matters worse. In December 2000, there was a international conference in South Africa whose stated purpose was to finalize an internationally binding treaty to ban what was called the dirty dozen, the twelve POPs -- or persistent organochlorine pollutants -- including, of course, DDT. The U.S. Senate is now planning to ratify the final version of the resulting treaty. (See ACSH's press release about the DDT anniversary and impending POPs treaty.)

An article entitled "Balancing Risks on the Backs of the Poor" in the July 2000 issue of the journal Nature Medicine called this attempt to broaden the ban on DDT "eco-colonialism that can impoverish no less than the imperial colonialism of the past did" and said it shows the developed world is once "again to embrace indifference, and the pursuit of environmental goals on the backs of the world's sickest and poorest." The charges are made because DDT is the most cost-effective means of fighting mosquitoes that carry malaria, which kills millions of people, mostly in poor countries, every year.

Environmentalists charge that DDT is dangerous to humans and animals, but the first study to find an elevated risk of breast cancer from exposure to DDT "has now failed to be replicated at least eight times," with some studies even finding "significantly" reduced risk Ð and there were similar findings for "multiple myeloma, hepatic cancer, and non-Hodgkin lymphoma" (Attaran et al. 2000, 731, 730). Amir Attaran, who was one of the leaders in the successful effort to prevent the total banning of DDT for disease (malaria) vector control, added that although "hundreds of millions (and perhaps billions) of people have been exposed to elevated concentrations of DDT...the literature does not contain even one peer-reviewed, independently replicated study linking DDT exposure to any adverse health outcome" (Attaran and Maharaj 2000).

In spite of the massive accumulation of evidence on the safety of DDT and other chemicals, there is a still steady drumbeat in the media about alleged cancer causing pesticides and chemical additives. The often unstated presumption is that "natural foods" are free of "chemicals," although what exactly that may mean is unclear, since plants do in fact consist of chemical constituents. Breast cancer still heads the list of the cancers that are alleged to be caused by "chemicals," with DDT, DDE [1,1dichloro2,2bis(pchlorophenyl) ethylene, the metabolite of DDT], and other organochlorines considered the worst culprits, though repeated studies have failed to bear out this fear.

The term "chemicals" has become a code word for all that is wrong with modern life. Bruce Ames has long argued that we ingest far more of the major carcinogens from the foods we eat than from additives or other "chemicals" in our food or environment: "Despite numerous suggestions to the contrary, there is no convincing evidence of any generalized increase in U.S. (or U.K.) cancer rates other than what could plausibly be ascribed to the delayed effects of previous increases in tobacco usage." Further, "there are large numbers of mutagens and carcinogens in every meal, all perfectly natural and traditional. Nature is not benign. It should be emphasized that no human diet can be entirely free of mutagens and carcinogens" (Ames 1983, 1261). Ames has demonstrated that some of the foods we eat also seem to provide protection against cancer and help the body's mechanisms for neutralizing some likely carcinogens. Though Ames is seen as the enemy by "natural foods" enthusiasts, they have picked up some of his ideas about foods (such as broccoli) being anti-oxidants and therefore anti-carcinogenic, and the "natural foods " enthusiasts act as if it was their own discovery or as if it was a validation of all their ideas about human health.

It was in the early days of the modern anti-chemical hysteria that DDT became a target for activists, leading to the ban. In their zeal for what they imagined to be chemical-free purity, they ignored the real costs and benefits of the ban. It is interesting to note that the December 31, 1972 EPA press release titled "DDT Ban Takes Effect," which decreed that the "general use of the pesticide DDT will no longer be legal in the United States after today," also conceded the enormous benefit to human health from the use of DDT. DDT was developed as the first of the modern insecticides early in World War II. It was initially used with great effect to combat malaria, typhus, and the other insect-borne human diseases among both military and civilian populations.

Perhaps 100 million lives were saved because of DDT's success in eradicating malaria, yet the public now thinks of it largely as one of those nasty chemicals that got banned because of noble activists.

The most positive outcome of the 2000 conference on POPs was the decision to allow countries, under certain circumstances (such as large epidemics), to opt out of the ban on DDT (31 have done this so far). Unfortunately, there are still many needless bureaucratic procedures that they are required to follow in order to use DDT to protect their citizens from malaria and other vector-borne diseases, and the treaty now being finalized will only make matters worse.

Given the massive evidence that has accumulated over the past half century on the safety of DDT and other chemicals Ð and the enormous benefits that we derive from them Ð we should not see these substances continually assaulted by groups whose members (like all their fellow citizens) have so enormously benefited from synthetic chemicals. It has been obvious for some time that large segments of the public are not going to be persuaded by any amount of evidence, no matter how overwhelming it may be. Responsible academics and researchers should continue to frame their arguments in terms of scientific evidence. At the same time, we will have to obtain a better understanding the environmentalists' anti-scientific mindset, which might be called POPs: Persistent Obtuse Perversity.

The phobia about DDT is part of a larger chemophobia with philosophical roots stretching back to the dawn of science and industry. There is a prevailing public sentiment that what is natural is safe until proved harmful, while what is created by man is harmful until proved safe.

Since science cannot provide absolute certainty of safety, campaigns of demonization that pit "nature" against science will always be difficult to counter. On issues such as DDT, we will continue to have a difficult time making our case, until the science education of the public is considerably improved.

Thomas R. DeGregori, Ph.D. is a professor of economics at the University of Houston and an ACSH Director who regularly works in malarial areas in Africa, Asia, and the Caribbean including those not benefiting from DDT protection and has taken the various anti-malarial medications described in the article