Look Who's Misrepresenting Science Now

Should DDT be reintroduced across the developing world to control mosquito-borne malaria? For several years now, conservative scholars at think tanks like the American Enterprise Institute have been beating the drums for this solution. Their secondary goal (I’ll grant them sincerity in wanting to end the several million deaths a year caused by malaria) is to bash the environmental movement, and by extension, Rachel Carson, whose 1962 book Silent Spring highlighted the environmental damage caused by widespread use of pesticides like DDT.

A number of high profile journalists have taken up this conservative cause. Sebastian Mallaby, writing in today’s Washington Post, called environmentalists’ failure to embrace the DDT solution for malaria “no different from the Bush administration’s indifference to scientific sense on climate change.” He follows in the footsteps of Tina Rosenberg of the New York Times, a writer I admire a lot, who a year-and-a-half ago in the Sunday Magazine issued a 4000-word clarion call headlined “What the World Needs Now is DDT.”

The trigger for Mallaby’s more recent outburst was hearings on Capitol Hill two weeks ago featuring several university scientists testifying that DDT does not do substantial environmental harm. The argument for DDT goes something like this: Most of the damage caused by DDT, which is less than Carson feared, occurs in animal species where the pesticide bio-accumulates and only then because of its widespread use in agriculture. Used sparingly around home portals and windows as mosquito repellant, it can be quite effective in reducing malaria incidence. Under such circumstances, its environmental effects are minimal.

Mallaby cites the examples of Uganda and South Africa, which had spectacular success in reducing the incidence of malaria by using DDT. He drew those examples from testimony offered by the AEI’s Roger Bate on the Hill a few weeks ago.

It’s too bad Mallaby didn’t go searching for the other side of the story. In his book, Bate cites the example of Sri Lanka, which all but eliminated malaria by spraying DDT in the 1960s. The disease reemerged only when the spraying stopped, according to Bate.

Wrong. As Gordon Harrison points out in his Mosquitoes, Malaria and Man, malaria in Sri Lanka didn't reemerge because DDT spraying stopped. It reemerged because the mosquitoes grew resistant to the pesticide. “Within a couple of years, so many Anopheles culicifacies survived that despite the spraying malaria spread in 1975 to more than 400,000 people. So in 1977 they switched to the more expensive malathion, and were able to reduce the number of cases to about 50,000 by 1980. In 2004, the number was down to 3,000, without using DDT,” wrote Harrison (thanks to Brad DeLong's website for this quote).

The Post headlined Mallaby’s column, “Look Who’s Ignoring Science Now.” DDT probably can provide some short-term help in many developing world situations. But history suggests the relief will only be temporary. Pundits who suggest it is quick fix are probably more interested in bashing environmentalists than in grappling with this issue’s complexity.