Science today is regularly distorted to serve other ends. The religious right, for instance, claims that "creationism" should be taught in public schools as a scientific alternative to the theory of evolution. The environmentalist left, for instance, claims that science reveals genetically modified foods to be harmful to one's health. Both groups subordinate the facts of science to other considerations, whether Biblical or ideological.
The same dishonesty is shaping the response to the Zika virus.
The Zika threat is causing great concern at the Rio Olympics, with some athletes having chosen to avoid the Games altogether rather than risk infection. Florida recently reported the first locally contracted cases of Zika in the United States. And the Centers for Disease Control is advising pregnant women not to travel to certain areas of Miami--the first time the agency has ever issued such a warning for the continental U.S.
But among the measures being taken around the world to combat this danger, one is notably absent: the use of DDT.
Zika is carried by mosquitoes, and DDT has been highly effective in eliminating mosquito-borne diseases. India, for example, had 75 million malaria cases in 1953, but only 50,000 by 1961, after DDT had been introduced. In Sri Lanka close to 3 million cases of malaria occurred in 1948; 15 years later, owing to DDT, the number dropped to 17. (Source.) The National Academy of Sciences stated in 1970: "To only a few chemicals does man owe as great a debt as to DDT.... It is estimated that in little more than two decades, DDT has prevented 500 million deaths due to malaria."
But strong opposition to DDT arose, spurred by the 1962 publication of Rachel Carson's Silent Spring. Environmentalists got DDT banned in the U.S. and, eventually, in dozens of other countries. Western nations, which fund anti-malaria campaigns throughout the world, largely refused to underwrite any efforts that employed DDT. As a result, DDT use shrank--and malaria surged.
In India the number of cases increased to 30 million in 1977. In Sri Lanka the number went to 2.5 million in 1969. (Source.) More recently, other forms of malaria control--such as installing bed-netting and reducing the presence of standing water--have lowered the incidence of the disease worldwide. But they are generally less effective than DDT. In South Africa, for example, after DDT spraying was halted in 1996, malaria infections rose from under 5,000 in 1995 to over 60,000 in 2000. At which point DDT was reintroduced--and six months later the number dropped by half. (Source.)
This hostility to DDT was not based on science. For instance, DDT was said to be carcinogenic, because of studies in which mice developed liver tumors--but only after receiving doses of DDT 100,000 times higher than what a person would typically absorb (source.) Further, the opponents of DDT ignored many facts contradicting their views--such as the fact that during the period of highest DDT use (1944-1972), deaths from liver cancer fell by 30 percent (source)--or that workers who regularly handled DDT were found to have no higher rates of cancer than the general population (source)--or that people who voluntarily ingested DDT daily for up to two years suffered no ill effects (source)--or that the amount of DDT (per kilogram of body weight) required to kill mice is greater than that of aspirin (source).
What, then, was the motive behind the anti-DDT crusade? It was based on the premise that the man-made is inherently suspect--that the natural is good and the non-natural is bad, that human "intervention" in nature is deleterious and that we have to protect nature from man, not for man. The millions of lives saved by our "non-organic" use of DDT--and the millions lost when it was not used--were disregarded. Instead, the thinning of the eggshells of the bald eagle was presented as an intolerable effect of DDT.
As explained by David Graber, a biologist with the National Park Service, environmentalists,
... value wilderness for its own sake, not for what value it confers upon mankind. . . . We are not interested in the utility of a particular species, or a free-flowing river or ecosystem to mankind. They have intrinsic value, more value--to me--than another human body or a billion of them.
True, there is evidence that some mosquitoes are developing resistance to DDT. But even where DDT's toxicity has been diminished, its repellent properties still work. When house walls are sprayed with DDT, even resistant mosquitoes are repulsed and don't enter. More important, though, one's attitude should be: "If DDT's effectiveness is lessening, let's find some way to make it work better." Instead, the operating premise seems to be: "Man-made chemicals interfere with nature, so let's find some way to prohibit them."
Man survives and prospers, not by living "in harmony" with nature, but by reshaping it--by creating houses and roads and factories out of the wilderness, by transforming nature into a tool that serves human purposes. The problem with environmentalists is not that they have an ideology, but that it is an ideology with an inverted standard of value. It is an ideology that regards the very means of human flourishing as destructive. In assessing DDT, therefore, if your overriding concern is to restructure nature in order to promote man's well-being, then you will focus on whether DDT does in fact save human lives. If, however, your overriding concern is to preserve nature against human encroachment, then you will focus on the "evil" of injecting chemicals into nature's domain. And you will be drawn to any arbitrary claim about adverse consequences of those chemicals.
My primary aim here is not to argue for the use of DDT, but to underscore the need for objectivity is dealing with such issues. We should not uncritically accept the assertions of those who are hostile to technology and industrialization. We should not accept any allegations of some product's harmfulness--say, that DDT causes Alzheimer's, or that vaccines cause autism or that fracking causes earthquakes--without being certain they rest on genuine, unpoliticized science.