At the time, that hypothesis was not unreasonable. The research linking smoking to cancer was fairly new, and very little was known about synthetic chemicals and human health. And while the rise in cancer may not have been as enormous as Carson made it out to be, it was real, and the possibility that all these new wonder chemicals were the source was truly scary.
Adding to the reasons to worry was a study conducted by a scientist named John Higginson—who later founded the World Health Organization’s agency for research on cancer—that compared cancerous tumors among Africans with those of African-Americans. Higginson discovered there was far more cancer in the second group. This indicated heredity was not among the bigger factors driving cancer. Based on this study and others, Higginson estimated that about two-thirds of all cancers had what he called an environmental cause. He didn’t mean environmental in the way that word came to be understood after Silent Spring, however. To Higginson, environmental simply meant anything that isn’t genetic. Even smoking was included. “Environment is what surrounds people and impinges on them,” he said in an interview with Science in 1979. “The air you breathe, the culture you live in, the agricultural habits of your community, the social cultural habits, the social pressures, the physical chemicals with which you come in contact, the diet, and so on.” As the science advanced, Higginson’s theory was vindicated and it became routine for cancer specialists to say that most cancers have environmental causes, but that only deepened the misunderstanding. “A lot of confusion has arisen in later days because most people have not gone back to the early literature, but have used the word ‘environment’ to mean chemicals,” Higginson said.
That mistaken belief is still widespread among environmental activists. “Cancer has been identified as an environmental disease—that is to say, it is unleashed in our cells by the absorption of toxic chemicals from our air, our water, our food,” wrote Bob Hunter, the cofounder of Greenpeace, in 2002 (who was battling prostate cancer at the time and would be killed by it three years later).
Higginson cited several reasons that his theory was misunderstood. One was the chemical industry’s blithe indifference to safety in the era prior to Silent Spring, which made it easy to see it as the villain of the cancer drama. And “Rachel Carson’s book was a watershed, as suddenly we became aware of the vast quantities of new chemicals, pollutants, pesticides, fibers and so forth in the environment.” Higginson also said environmentalists “found the extreme view convenient because of the fear of cancer. If they could possibly make people believe that cancer was going to result from pollution, this would enable them to facilitate the clean-up of water, of the air, or whatever it was. Now I’m all for cleaning up the air, and all for cleaning up trout streams, and all for preventing Love Canals, but I don’t think we should use the wrong argument for doing it. To make cancer the whipping boy for every environmental evil may prevent effective action when it does matter, as with cigarettes.”
Higginson was careful not to accuse environmentalists of deliberate dishonesty. It was more a case of excessive zeal. “People would love to be able to prove that cancer is due to pollution or the general environment. It would be so easy to say ‘let us regulate everything to zero exposure and we have no more cancer.’ The concept is so beautiful that it will overwhelm a mass of facts to the contrary.” That “mass of facts” included the observation that “there are few differences in cancer patterns between the polluted cities and the clean cities,” Higginson said. “You can’t explain why Geneva, a non-industrial city, has more cancer than Birmingham in the polluted central valleys of England.”
That was 1979. Since then, the “mass of facts” has grown steadily and today there is a consensus among leading cancer researchers that traces of synthetic chemicals in the environment—the stuff that turns up in blood tests of ordinary people—are not a major cause of cancer. “Exposure to pollutants in occupational, community, and other settings is thought to account for a relatively small percentage of cancer deaths,” says the American Cancer Society in Cancer Facts & Figures 2006. Of those, occupational exposures—workers in aluminum smelters, miners who dug asbestos under the unsafe conditions of the past—are by far the biggest category, responsible for perhaps 4 percent of all cancer. The ACS estimates that only 2 percent of all cancers are the result of exposure to “man-made and naturally occurring” environmental pollutants—a massive category that includes everything from naturally occurring radon gas to industrial emissions to car exhaust.
It’s critical to understand that not all carcinogenic chemicals in the environment are man-made. Far from it. To take just one example, countless plants produce carcinogenic chemicals as defenses against insects and other predators, so our food is positively riddled with natural carcinogens. They are in coffee, carrots, celery, nuts, and a long, long list of other produce. Bruce Ames, a leading cancer scientist at the University of California at Berkeley, estimates that “of all dietary pesticides people eat, 99.99 percent are natural” and half of all chemicals tested—synthetic and natural—cause cancer in high-dose lab animal experiments. So it’s highly likely that synthetic chemicals are responsible for only a small fraction of the 2 percent of cancers believed to be caused by environmental pollution; Ames believes the precise figure is much less than 1 percent.
Major health organizations agree that traces of synthetic chemicals in the environment are not a large risk factor. What is hugely important is lifestyle. Smoking, drinking, diet, obesity, and exercise: These things make an enormous difference—by most estimates, accounting for roughly 65 percent of all cancers. As early as the 1930s, researchers found that cancer rates were higher in the rich world than the poor, a division that continues to this day thanks to differences in lifestyle. “The total cancer burden is highest in affluent societies, mainly due to a high incidence of tumors associated with smoking and Western lifestyle,” the World Health Organization noted in its World Cancer Report. There’s an obvious paradox here. Those of us living in wealthy societies are enormously lucky, but it is precisely that wealth which supports a lifestyle that, in many ways, promotes cancer.
None of this has persuaded the legion of environmentalists, activists, and concerned citizens campaigning against chemicals they believe are a major cause—some would say the major cause—of cancer. The interesting question is why. When there is such widespread scientific agreement, why do people persist in believing the opposite? There are several answers, but the most profound was hinted at by John Higginson in that 1979 interview. “I think that many people had a gut feeling that pollution ought to cause cancer,” he said.
Paul Slovic’s surveys revealed how true that is. Large majorities in the United States, Canada, and France said they avoided chemicals as much as possible, they wouldn’t drink tap water that had even a tiny amount of a cancer-causing substance, and they believed that someone exposed to a chemical that can cause cancer “will probably get cancer some day.” For these people, it would seem obvious that having carcinogenic chemicals floating in our bodies is a major threat.