The Lessons Of The DDT Ban

The New York Times has a piece on how DDT is returning as an effective control agent in the fight against malaria. After Rachel Carlson’s shoddily-researched Silent Spring motivated governmental agencies and NGOs to push for a virtual ban on the anti-mosquito agent, the subsequent explosion in the preventable disease has caused scientists to take a second look. Despite the anti-DDT fervor of the last few decades, DDT is effective in stopping human contact with infected mosquitos:

From the 1940s onward, DDT was used to kill agricultural pests and disease-carrying insects because it was cheap and lasted longer than other insecticides. DDT helped much of the developed world, including the United States and Europe, eradicate malaria. Then in the 1970s, after the publication of Rachel Carson’s “Silent Spring,” which raised concern over DDT’s effects on wildlife and people, the chemical was banned in many countries. Birds, especially, were said to be vulnerable, and the chemical was blamed for reduced populations of bald eagles, falcons and pelicans. Scientific scrutiny has failed to find conclusive evidence that DDT causes cancer or other health problems in humans.

Today, indoor DDT spraying to control malaria in Africa is supported by the World Health Organization; the Global Fund to Fight AIDS, Tuberculosis and Malaria; and the United States Agency for International Development.

The remaining concern has been that the greater use of DDT in Africa would only lead mosquitoes to develop resistance to it. Decades ago, such resistance developed wherever DDT crop spraying was common. After the DDT bans went into effect in the United States and elsewhere, it continued to be used extensively for agriculture in Africa, and this exerted a powerful pressure on mosquitoes there to develop resistance. Although DDT is now prohibited for crop spraying in Africa, a few mosquito species there are still resistant to it. But DDT has other mechanisms of acting against mosquitoes beyond killing them. It also functions as a “spatial repellent,” keeping mosquitoes from entering areas where it has been sprayed, and as a “contact irritant,” making insects that come in contact with it so irritated they leave.

The DDT ban, as a consequence of environmentalist hysteria has resulted in an explosion of malaria throughout the developing world that has claimed millions of lives to a preventable disease. In terms of human catastrophes, the DDT ban has been one of the most horrendous misuses of science in human history — and its impact has irreparably harmed the developing world.

The lesson of the DDT ban gives us a stern warning about the problems of succumbing to interest-group hysteria — as other interest groups flog their pet policies, they tend to be blind to the consequences of those policies. The DDT ban was based on poor science and policymaking motivated largely by interest group politics. Such a combination is usually deadly.

As Glenn Reynold quips:

The debate over DDT is over. There’s scientific consensus. Anyone who disagrees is a DDT denialist and a mouthpiece for Big Mosquito.

Sadly, that sort of logic is all too prevalent, and it’s precisely that combination of shaky science and interest groups playing the politics of fear that led to the disastrous ban on DDT. With the hysteria over global warming reaching a fever pitch, the possibility of the developing world once again being irreparably harmed by the fear of others remains all too prescient. Millions died because of DDT hysteria. How many millions more will die due to the global warming scare?

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