DDT and Malaria -- Again

The conservative campaign to make DDT a centerpiece of malaria control efforts in Africa continues unabated, and today the Alternet news service ran an insightful if long-winded article that provides a decent overview of the issues. Journalist Kim Larsen early on points out that DDT even when used only for indoor residual spraying is no magic bullet, largely because mosquitoes develop resistance. Allow me to quote her at length:

Today's most ardent proponents of DDT suggest that the sole obstacle to routing malaria half a century ago was the onset of the environmental movement. Mosquito resistance to DDT and the crippling logistics of effective spraying campaigns are overlooked in favor of the much juicier target of Rachel Carson and her green descendants. Carson's 1962 book, Silent Spring, was indeed a watershed. Invoking DDT as Exhibit A and sounding her alarms in graceful, elegiac prose, Carson awakened readers to the idea that pesticides might have a downside.

The use of DDT was banned in the United States in 1972. But while the chemical is no longer manufactured here, other organochlorine compounds are, and many are or are likely to be subject to scrutiny by regulators. This may be what really concerns DDT's more aggressive advocates in the private sector. In a chapter of a book on "message crafting," economist Roger Bate, a fellow at the Competitive Enterprise Institute, warns, "DDT may be today's target, but it's not going to be long before chemicals that the industry cares about are added to the POPs Convention and other chemicals regulations."

DDT proponents are generally reluctant to acknowledge the complicating and protean factor of mosquito resistance. Entomologist May Berenbaum finds this galling. An expert on insecticide metabolism, Berenbaum is director of the entomology department at the University of Illinois at Urbana-Champaign. "Read the entomological literature of the 1950s," she said in a telephone interview. "Way before Silent Spring, scientists were already trying to understand resistance. That's what insecticide toxicology was all about back then. Resistance to DDT was first detected in Italy, in houseflies, in 1947!"

Environmentalists' objections to DDT, Berenbaum said, were just one piece of an intricate puzzle. In a 2005 Washington Post article that discussed mosquito resistance to DDT, she warned: "Overselling a chemical's capacity to solve a problem can do irretrievable harm not only by raising false hopes but by delaying the use of more effective long-term methods."

After Berenbaum published the article, she said, she was barraged by e-mails demanding that she support her claims. "To get them off my back, I finally culled a list of peer-reviewed articles documenting resistance to DDT and other pesticides in pockets all over Africa. This is not my life's work. I spent 10 minutes--10 minutes--and I found 15 articles. What would I have found if I'd spent an hour?"

She concludes:

DDT will continue to play some role as a front-line weapon in the malaria wars. But it is also a distraction. DDT won't pave a watercourse or feed a child or provide a job, and at the end of the day, malaria is a development issue.