June 12, 2002

Silent Spring at 40

Rachel Carson’s classic is not aging well.

The modern environmentalist movement was launched at the beginning of June 1962, when excerpts from what would become Rachel Carson’s anti-chemical landmark Silent Spring were published in The New Yorker. "Without this book, the environmental movement might have been long delayed or never have developed at all," declared then-Vice President Albert Gore in his introduction to the 1994 edition. The foreword to the 25th anniversary edition accurately declared, "It led to environmental legislation at every level of government."

In 1999 Time named Carson one of the "100 People of the Century." Seven years earlier, a panel of distinguished Americans had selected Silent Spring as the most influential book of the previous 50 years. When I went in search of a copy recently, several bookstore owners told me they didn’t have any in stock because local high schools still assign the book and students had cleaned them out.

Carson worked for years at the U.S. Fish and Wildlife Service, eventually becoming the chief editor of that agency’s publications. Carson achieved financial independence in the 1950s with the publication of her popular celebrations of marine ecosystems, The Sea Around Us and The Edge of the Sea. Rereading Silent Spring reminds one that the book’s effectiveness was due mainly to Carson’s passionate, poetic language describing the alleged horrors that modern synthetic chemicals visit upon defenseless nature and hapless humanity. Carson was moved to write Silent Spring by her increasing concern about the effects of pesticides on wildlife. Her chief villain was the pesticide DDT.

The 1950s saw the advent of an array of synthetic pesticides that were hailed as modern miracles in the war against pests and weeds. First and foremost of these chemicals was DDT. DDT’s insecticidal properties were discovered in the late 1930s by Paul Muller, a chemist at the Swiss chemical firm J.R. Geigy. The American military started testing it in 1942, and soon the insecticide was being sprayed in war zones to protect American troops against insect-borne diseases such as typhus and malaria. In 1943 DDT famously stopped a typhus epidemic in Naples in its tracks shortly after the Allies invaded. DDT was hailed as the "wonder insecticide of World War II."

As soon as the war ended, American consumers and farmers quickly adopted the wonder insecticide, replacing the old-fashioned arsenic-based pesticides, which were truly nasty. Testing by the U.S. Public Health Service and the Food and Drug Administration’s Division of Pharmacology found no serious human toxicity problems with DDT. Muller, DDT’s inventor, was awarded the Nobel Prize in 1948.

DDT was soon widely deployed by public health officials, who banished malaria from the southern United States with its help. The World Health Organization credits DDT with saving 50 million to 100 million lives by preventing malaria. In 1943 Venezuela had 8,171,115 cases of malaria; by 1958, after the use of DDT, the number was down to 800. India, which had over 10 million cases of malaria in 1935, had 285,962 in 1969. In Italy the number of malaria cases dropped from 411,602 in 1945 to only 37 in 1968.

The tone of a Scientific American article by Francis Joseph Weiss celebrating the advent of "Chemical Agriculture" was typical of much of the reporting in the early 1950s. "In 1820 about 72 per cent of the population worked in agriculture, the proportion in 1950 was only about 15 per cent," reported Weiss. "Chemical agriculture, still in its infancy, should eventually advance our agricultural efficiency at least as much as machines have in the past 150 years." This improvement in agricultural efficiency would happen because "farming is being revolutionized by new fertilizers, insecticides, fungicides, weed killers, leaf removers, soil conditioners, plant hormones, trace minerals, antibiotics and synthetic milk for pigs."

In 1952 insects, weeds, and disease cost farmers $13 billion in crops annually. Since gross annual agricultural output at that time totaled $31 billion, it was estimated that preventing this damage by using pesticides would boost food and fiber production by 42 percent. Agricultural productivity in the United States, spurred by improvements in farming practices and technologies, has continued its exponential increase. As a result, the percentage of Americans living and working on farms has dropped from 15 percent in 1950 to under 1.8 percent today.

But DDT and other pesticides had a dark side. They not only killed the pests at which they were aimed but often killed beneficial organisms as well. Carson, the passionate defender of wildlife, was determined to spotlight these harms. Memorably, she painted a scenario in which birds had all been poisoned by insecticides, resulting in a "silent spring" in which "no birds sing."

The scientific controversy over the effects of DDT on wildlife, especially birds, still vexes researchers. In the late 1960s, some researchers concluded that exposure to DDT caused eggshell thinning in some bird species, especially raptors such as eagles and peregrine falcons. Thinner shells meant fewer hatchlings and declining numbers. But researchers also found that other bird species, such as quail, pheasants, and chickens, were unaffected even by large doses DDT.

On June 14, 1972, 30 years ago this week, the EPA banned DDT despite considerable evidence of its safety offered in seven months of agency hearings. After listening to that testimony, the EPA’s own administrative law judge declared, "DDT is not a carcinogenic hazard to man...DDT is not a mutagenic or teratogenic hazard to man...The use of DDT under the regulations involved here [does] not have a deleterious effect on freshwater fish, estuarine organisms, wild birds or other wildlife." Today environmental activists celebrate the EPA’s DDT ban as their first great victory.

Carson argued that DDT and other pesticides were not only harming wildlife but killing people too. The1958 passage by Congress of the Delaney Clause, which forbade the addition of any amount of chemicals suspected of causing cancer to food, likely focused Carson’s attention on that disease.

For the previous half-century some researchers had been trying to prove that cancer was caused by chemical contaminants in the environment. Wilhelm Hueper, chief of environmental cancer research at the National Cancer Institute and one of the leading researchers in this area, became a major source for Carson. Hueper was so convinced that trace exposures to synthetic chemicals were a major cause of cancer in humans that he totally dismissed the notion that smoking cigarettes caused cancer. The assertion that pesticides were dangerous human carcinogens was a stroke of public relations genius. Even people who do not care much about wildlife care a lot about their own health and the health of their children.

In 1955 the American Cancer Society predicted that "cancer will strike one in every four Americans rather than the present estimate of one in five." The ACS attributed the increase to "the growing number of older persons in the population." The ACS did note that the incidence of lung cancer was increasing very rapidly, rising in the previous two decades by more than 200 percent for women and by 600 percent for men. But the ACS also noted that lung cancer "is the only form of cancer which shows so definite a tendency." Seven years later, Rachel Carson would call her chapter on cancer "One in Four."

To bolster her case for the dangers of DDT, Carson improperly cited cases of acute exposures to the chemical as proof of its cancer-causing ability. For example, she told the story of a woman who sprayed DDT for spiders in her basement and died a month later of leukemia. In another case, a man sprayed his office for cockroaches and a few days later was diagnosed with aplastic anemia. Today cancer specialists would dismiss out of hand the implied claims that these patients’ cancers could be traced to such specific pesticide exposures. The plain fact is that DDT has never been shown to be a human carcinogen even after four decades of intense scientific scrutiny.

Carson was also an effective popularizer of the idea that children were especially vulnerable to the carcinogenic effects of synthetic chemicals. "The situation with respect to children is even more deeply disturbing," she wrote. "A quarter century ago, cancer in children was considered a medical rarity. Today, more American school children die of cancer than from any other disease [her emphasis]." In support of this claim, Carson reported that "twelve per cent of all deaths in children between the ages of one and fourteen are caused by cancer."

Although it sounds alarming, Carson’s statistic is essentially meaningless unless it’s given some context, which she failed to supply. It turns out that the percentage of children dying of cancer was rising because other causes of death, such as infectious diseases, were drastically declining.

In fact, cancer rates in children have not increased, as they would have if Carson had been right that children were especially susceptible to the alleged health effects of modern chemicals. Just one rough comparison illustrates this point: In 1938 cancer killed 939 children under 14 years old out of a U.S. population of 130 million. In 1998, according to the National Cancer Institute, about 1,700 children died of cancer, out of a population of more than 280 million. In 1999 the NCI noted that "over the past 20 years, there has been relatively little change in the incidence of children diagnosed with all forms of cancer; from 13 cases per 100,000 children in 1974 to 13.2 per 100,000 children in 1995."

Clearly, if cancer incidence isn’t going up, modern chemicals can’t be a big factor in cancer. But this simple point is lost on Carson’s heirs in the environmental movement, who base their careers on pursuing phantom risks. The truth is that both cancer mortality and incidence rates have been declining for about a decade, mostly because of a decrease in the number of cigarette smokers.

The Great Cancer Scare launched by Carson, and perpetuated by her environmentalist disciples ever since, should have been put to rest by a definitive 1996 report from the National Academy of Sciences, Carcinogens and Anticarcinogens in the Human Diet. The NAS concluded that levels of both synthetic and natural carcinogens are "so low that they are unlikely to pose an appreciable cancer risk." Worse yet from the point of view of anti-chemical crusaders, the NAS added that Mother Nature’s own chemicals probably cause more cancer than anything mankind has dreamed up: "Natural components of the diet may prove to be of greater concern than synthetic components with respect to cancer risk."

Meanwhile, Carson’s disciples have managed to persuade many poor countries to stop using DDT against mosquitoes. The result has been an enormous increase in the number of people dying of malaria each year. Today malaria infects between 300 million and 500 million people annually, killing as many 2.7 million of them. Anti-DDT activists who tried to have the new U.N. treaty on persistent organic pollutants totally ban DDT have stepped back recently from their ideological campaign, conceding that poor countries should be able to use DDT to control malaria-carrying mosquitoes.

So 40 years after the publication of Silent Spring, the legacy of Rachel Carson is more troubling than her admirers will acknowledge. The book did point to problems that had not been adequately addressed, such as the effects of DDT on some wildlife. And given the state of the science at the time she wrote, one might even make the case that Carson’s concerns about the effects of synthetic chemicals on human health were not completely unwarranted. Along with other researchers, she was simply ignorant of the facts. But after four decades in which tens of billions of dollars have been wasted chasing imaginary risks without measurably improving American health, her intellectual descendants don’t have the same excuse.

Ronald Bailey is Reason's science correspondent and the editor of Earth Report 2000: Revisiting the True State of the Planet(McGraw-Hill)