It's a staple of environmentalist dogma that industrial chemicals and pesticides are causing an epidemic of human cancers. Worldwatch Institute founder Lester Brown, for example, declared last year that "Every human being harbors in his or her body about 500 synthetic chemicals that were nonexistent before 1920." Such claims are often accompanied by pleas for new regulations removing even the smallest traces of synthetic chemicals from the environment.
But is there a rising cancer epidemic? Not according to Cancer Facts and Figures 2001, recently issued by the American Cancer Society. "Overall cancer incidence and death rates have continued to decrease in men and women since the early 1990s, and the decline in overall cancer mortality has been greater in recent years," the report concludes. The National Cancer Institute's annual report for 2000 similarly found that "the number of new cancer cases per 100,000 persons per year" for all cancers combined declined on average 0.8 percent per year between 1990 and 1997." According to the institute, the incidence of cancer has declined by 1.3 percent per year since 1992.
A lot of the cancer furor can be traced to the seemingly dramatic increases in breast and prostate cancer during the 1980s. "The apparent increases in the incidence of breast and prostate cancer are mostly due to increased screening," reports Mary Beth Hill-Harmon, an epidemiologist with the American Cancer Society. In other words, doctors got better at detecting breast and prostate cancers earlier, and this artificially—and temporarily—pumped up their numbers. Breast cancer rates have been roughly constant since 1987, and breast cancer death rates dropped 2.2 percent per year from 1990 to 1997. Prostate cancer death rates decreased by 4.4 percent annually from 1994 to 1997.
Meanwhile, colon and rectal cancer death rates have been decreasing 1.8 percent per year since 1984. Lung cancer death rates dropped among men by 1.7 percent per year from 1990 to 1997. The five-year survival rate for all cancers combined is now 60 percent. These improvements are largely a result of earlier detection (the sooner it's discovered, the more easily the disease is treated) and the development of more effective therapies.
No rising epidemic then. But perhaps the declines in cancer rates are a result of regulations reining in industrial chemicals? That's unlikely, since very few cancers are caused by synthetic chemicals in the first place. Sir Richard Doll, head of the Clinical Trial Service & Epidemiological Studies Unit in Britain, estimates that only 1 to 5 percent of cancers can be attributed to pollution.
The biggest cause of the disease is smoking, which is responsible for about 30 percent of cancers. Diet—especially consumption of animal fat—is responsible for between 20 and 50 percent; infections are responsible for 10 to 20 percent; and natural reproductive hormones account for 10 to 20 percent. A good portion of the decreases in both cancers and cancer deaths can be attributed to sharp declines in the number of smokers.
That's all good news, of course, even if it does burst the bubbles of the Lester Browns of the world. Here's some bad news: Further reductions in cancer rates depend on persuading people to improve their diets and stop smoking. Both are easier said than done.