Silent Spring.

Rachel Carson's Silent Spring (1962) became the inspiration for the environmental movement. Its elegant prose expressed passionate outrage at the ravaging of beautiful, unspoiled nature by man. Its frightening message was that we are all being injured by deadly poisons (DDT and other pesticides) put out by a callous chemical industry. This message was snapped up by intellectuals, and the book sold over a million copies. Many organizations have sprung up to spread Carson's message.

Rachel Carson set the style for environmentalism. Exaggeration and omission of pertinent contradictory evidence are acceptable for the holy cause.

The book starts with a romanticized vision of a world in harmony, followed by a horror story of an "evil spell that settled on the community: mysterious maladies swept the flocks of chickens; the cattle and sheep sickened and died....Children...would be stricken and die within a few hours....The few birds seen anywhere were moribund...and could not fly....a white granular powder...had fallen like snow upon the roofs and the lawns, the fields and the streams."

The powder was DDT, which actually saved tens of millions of lives, more than any substance in history, with the possible exception of antibiotics. The benefits of DDT were omitted from the book. Silent Spring said the American robin was "on the verge of extinction," yet Roger Tory Peterson (the dean of American ornithologists) said it was the most numerous bird on the continent. DDT was highly toxic to mosquitoes but of very low toxicity to honey bees and higher animals. In the Third World, DDT saved the lives of millions of children who otherwise would have been exposed to malaria and other insect-borne diseases.

DDT displaced the more toxic and persistent lead arsenate. DDT was the first of a series of synthetic agricultural chemicals that have advanced public health by increasing the supply and reducing the price of fruits and vegetables. People who eat few fruits and vegetables, compared to those who eat about four or five portions a day, have about double the cancer rate for most types of cancer and run an increased risk of heart disease and cataracts as well. Thus, pesticides lead to lower cancer rates and improved health. Life expectancy has steadily increased in our era of pesticides. Pesticide residues in food are trivial in terms of cancer causation or toxicity. There has never been any convincing evidence that DDT (or pesticide residues in food) has ever caused cancer in man or that DDT had a significant impact on the population of our eagles or other birds.

Carson's fundamental misconception was: "For the first time in the history of the world, every human being is now subjected to contact with dangerous chemicals, from the moment of conception until death." This is nonsense: Every chemical is dangerous if the concentration is too high. Moreover, 99.9 percent of the chemicals humans ingest are natural. For example, 99.99 percent of the pesticides humans eat are natural pesticides produced by plants to kill off predators. About half of all natural chemicals tested at high dose, including natural pesticides, cause cancer in rodents. People determined to rid the world of synthetic chemicals refuse to face these facts. Risk assessment methods build in huge safety factors for synthetic chemicals, while natural chemicals are ignored. Current policy diverts enormous resources from important to unimportant risks.

Bruce N. Ames is a professor of biochemistry and molecular biology and Thomas Jukes is a professor of biophysics at the University of California, Berkeley.