Developing resistance
At one level, these articles send a comforting message to the developed world: Saving African children is easy. We don’t need to build large aid programs or fund major health initiatives, let alone develop Third World infrastructure or think about larger issues of fairness. No, to save African lives from malaria, we just need to put our wallets away and work to stop the evil environmentalists.
Unfortunately, it’s not so easy.
For one thing, there is no global DDT ban. DDT is indeed banned in the U.S., but malaria isn’t exactly a pressing issue here. If it ever were, the ban contains an exception for matters of public health. Meanwhile, it’s perfectly legal—and indeed, used—in many other countries: 10 out of the 17 African nations that currently conduct indoor spraying use DDT (New York Times, 9/16/06).
DDT use has decreased enormously, but not because of a ban. The real reason is simple, although not one conservatives are particularly fond of: evolution. Mosquito populations rapidly develop resistance to DDT, creating enzymes to detoxify it, modifying their nervous systems to avoid its effects, and avoiding areas where DDT is sprayed — and recent research finds that that resistance continues to spread even after DDT spraying has stopped, lowering the effectiveness not only of DDT but also other pesticides (Current Biology, 8/9/05).
“No responsible person contends that insect-borne disease should be ignored,” Carson wrote in Silent Spring. “The question that has now urgently presented itself is whether it is either wise or responsible to attack the problem by methods that are rapidly making it worse. . . . Resistance to insecticides by mosquitoes . . . has surged upwards at an astounding rate.”
Unfortunately, her words were ignored. Africa didn’t cut back on pesticides because, through a system called the “Industry Cooperative Program,” the pesticide companies themselves got to participate in the United Nations agency that provided advice on pest control. Not surprisingly, it continued to recommend significant pesticide usage.
When Silent Spring came out in 1962, it seemed as if this strategy was working. To take the most extreme case, Sri Lanka counted only 17 cases of malaria in 1963. But by 1969, things had once again gotten out of hand: 537,700 cases were counted. Naturally, the rise had many causes: Political and financial pressure led to cutbacks on spraying, stockpiles of supplies had been used up, low rainfall and high temperatures encouraged mosquitoes, a backlog of diagnostic tests to detect malaria was processed and testing standards became more stringent. But even with renewed effort, the problem did not go away.
Records uncovered by entomologist Andrew Spielman hint at why (Mosquito, p. 177). For years, Sri Lanka had run test programs to verify DDT’s effectiveness at killing mosquitoes. But halfway through the program, their standards were dramatically lowered. “Though the reason was not recorded,” Spielman writes, “it was obvious that some mosquitoes were developing resistance and the change was made to justify continued spraying.”
But further spraying led only to further resistance, and the problem became much harder to control. DDT use was scaled back and other pesticides were introduced—more cautiously this time—but the epidemic was never again brought under control, with the deadly legacy that continues to this day.
Instead of apologizing, the chemical companies went on the attack. They funded front groups and think tanks to claim the epidemic started because countries “stopped” using their products. In their version of the story, environmentalists forced Africans to stop using DDT, causing the increase in malaria. “It’s like a hit-and-run driver who, instead of admitting responsibility for the accident, frames the person who tried to prevent the accident,” complains Tim Lambert, whose weblog, Deltoid, tracks the DDT myth and other scientific misinformation in the media.
