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Commentary

Fateful Voice of a Generation Still Drowns Out Real Science
John Tierney, The New York Times, 6-5-07

Tierney argues that the celebration of Rachel Carson's Silent Spring skips blithely over the millions of lives lost from malaria in developing nations—which could have been saved by prudent use of pesticides like DDT. Read the whole thing.

Ms. Carson used dubious statistics and anecdotes (like the improbable story of a woman who instantly developed cancer after spraying her basement with DDT) to warn of a cancer epidemic that never came to pass. She rightly noted threats to some birds, like eagles and other raptors, but she wildly imagined a mass "biocide." She warned that one of the most common American birds, the robin, was "on the verge of extinction"—an especially odd claim given the large numbers of robins recorded in Audubon bird counts before her book.

Ms. Carson's many defenders, ecologists as well as other scientists, often excuse her errors by pointing to the primitive state of environmental and cancer research in her day. They argue that she got the big picture right: without her passion and pioneering work, people wouldn't have recognized the perils of pesticides. But those arguments are hard to square with Dr. Baldwin's review.

Dr. Baldwin led a committee at the National Academy of Sciences studying the impact of pesticides on wildlife. (Yes, scientists were worrying about pesticide dangers long before "Silent Spring.") In his review, he praised Ms. Carsons's literary skills and her desire to protect nature. But, he wrote, "Mankind has been engaged in the process of upsetting the balance of nature since the dawn of civilization."

While Ms. Carson imagined life in harmony before DDT, Dr. Baldwin saw that civilization depended on farmers and doctors fighting "an unrelenting war" against insects, parasites and disease. He complained that "Silent Spring" was not a scientific balancing of costs and benefits but rather a "prosecuting attorney's impassioned plea for action."

Ms. Carson presented DDT as a dangerous human carcinogen, but Dr. Baldwin said the question was open and noted that most scientists "feel that the danger of damage is slight." He acknowledged that pesticides were sometimes badly misused, but he also quoted an adage: "There are no harmless chemicals, only harmless use of chemicals."

Ms. Carson, though, considered new chemicals to be inherently different. "For the first time in the history of the world," she wrote, "every human being is now subjected to contact with dangerous chemicals, from the moment of conception until death."

She briefly acknowledged that nature manufactured its own carcinogens, but she said they were "few in number and they belong to that ancient array of forces to which life has been accustomed from the beginning." The new pesticides, by contrast, were "elixirs of death," dangerous even in tiny quantities because humans had evolved "no protection" against them and there was "no 'safe' dose."

She cited scary figures showing a recent rise in deaths from cancer, but she didn't consider one of the chief causes: fewer people were dying at young ages from other diseases (including the malaria that persisted in the American South until DDT). When that longevity factor as well as the impact of smoking are removed, the cancer death rate was falling in the decade before "Silent Spring," and it kept falling in the rest of the century.

Why weren't all of the new poisons killing people? An important clue emerged in the 1980s when the biochemist Bruce Ames tested thousands of chemicals and found that natural compounds were as likely to be carcinogenic as synthetic ones. Dr. Ames found that 99.99 percent of the carcinogens in our diet were natural, which doesn't mean that we are being poisoned by the natural pesticides in spinach and lettuce. We ingest most carcinogens, natural or synthetic, in such small quantities that they don't hurt us. Dosage matters, not whether a chemical is natural, just as Dr. Baldwin realized.

But scientists like him were no match for Ms. Carson's rhetoric. DDT became taboo even though there wasn't evidence that it was carcinogenic (and subsequent studies repeatedly failed to prove harm to humans)...

The human costs have been horrific in the poor countries where malaria returned after DDT spraying was abandoned. Malariologists have made a little headway recently in restoring this weapon against the disease, but they've had to fight against Ms. Carson's disciples who still divide the world into good and bad chemicals, with DDT in their fearsome "dirty dozen."



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