Malaria, from the Italian for "bad air," is an often-deadly parasitical disease carried by several different species of mosquito. According to the World Health Organization, in 2006 roughly 1 million people died of the disease, and 247 million were infected [1]. It is more common in "third-world" nations, and often thought of as a tropical disease - but the truth is it was once found all over the United States. One big aid in its eradication was the widespread spraying of the contact poison DDT, or dichlorodiphenyltrichloroethane.
As a killer of malaria carrying mosquitoes (and other insects and their associated diseases), DDT is cheap and long-lasting. That low-cost is particularly important because many of the nations where malaria is still a problem are quite poor. When used for health purposes, it is often sprayed on the inside walls of houses. It continues to be effective for a long time, only requiring spraying once or twice a year.
And, it works. In 1970, the National Academy of Sciences stated that "in little more than two decades, DDT has prevented 500 million human deaths due to malaria that would have otherwise been inevitable [2]." South Africa, which used DDT until 1996, abandoned it under environmental pressure, then began using it again in 2000, provides an interesting case study.
From 1971-1996, the number of malaria cases in the country remained under 10,000. After abandoning DDT, the number shot up to a peak of around 65,000 in 2000. By 2003, the number was back down to around 10,000. [3]
So, DDT sounds great, right? So why was it banned in America, and should it be illegal? The answer begins with a book by Rachel Carson called "Silent Spring," and a then-nascent EPA. In her book, published in 1962, Carson popularized what she believed were the dangers of some synthetic chemicals, especially DDT.
Several environmental groups soon began lobbying the federal government to ban the chemical. The EPA, soon after its formation in 1970, held hearings on the risks of DDT. At the end of the hearings, Edmund Sweeney, the head examiner, announced that the scientific evidence provided no basis for a ban. The head of the EPA, William Ruckelshaus, who didn't attend a single hearing, overruled him, and a ban went into effect.
Why did he do this? The EPA was a brand new agency at the time. It has been suggested based on statements of some of the ban advocates that "it was important for the EPA and environmentalists to succeed in banning DDT, so that their success would afford them greater powers to act in other areas [3]."
Afterwards, when the US and also the UN would no longer provide financial support for DDT, its use worldwide dropped, likely helping allow a huge number of preventable deaths in the undeveloped world. In 2006, the World Health Organization finally changed its mind, and decided once again to support the use of DDT. [3,4]
This isn't an EPA hearing, but we can also consider a few of the specific negative effects DDT was, and is, alleged to have. It is a fact that DDT and its products accumulate in fat tissue. However, according to a summary paper put out by the Cato Institute, "no scientific study has been able to replicate a case of actual human harm from DDT."
It has been classified as a possible carcinogen, but at a lower level than coffee. This same paper mentions that employees at a particular DDT production facility in India whose medical histories were tracked. appeared to suffer no ill effects. [3]
Perhaps you think it would be worth the death of a million birds to save a human life - that dilemma I won't try to answer for you. But we can also consider the effects on non-human animals. If you ask a man on the street to name a problem caused by DDT, his most likely answer will be, "it thins the egg shells of birds," with resultant problems in reproduction. To this, we must say two things.
First, DDT can be used agriculturally, and residentially. If it is sprayed only inside homes, or on mosquito netting, it is unlikely to greatly affect the bird population in any way whatsoever. Used agriculturally, it could. Whether it causes egg shells to thin is not without controversy, although most would say it does have an effect, particularly in sensitive raptors. [5]
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The four sources below were used in gathering the facts in this article. I particularly recommend #3 if you want to learn more about this issue. #2,4 is an excellent book, but the malaria/DDT discussion is only a small part of it.
[1] WHO | Malaria
[2] Quoted in "Liberty and Tyranny," by Mark Levin, p. 117
[3] South Africa's War against Malaria, by Richard Tren and Roger Bate
[4] Levin., p. 116-120
[5] DDT, Eggshells, and Me, by Robert Bailey