Is Radiation Good For You?

Any idiot should be able to poison a plant. That's what Edward Calabrese thought in 1966 as a junior at Bridgewater State College in Massachusetts. He was in a plant physiology class at the time, and his lab group had been told to dose some peppermint with an herbicide called Phosfon. The idea was to measure how much a given dose stunted the plant's growth, thereby demonstrating a fundamental tenet of biology: The more you poison something, the sicker it gets. In Calabrese's case, though, the lesson backfired. Instead of shriveling, the crop grew green and luxuriant. "Either you treated the plants with the wrong chemical, or you mislabeled them," the professor said. "God forbid, you discovered something new."     When Calabrese next tried to repeat the experiment, the peppermint shriveled as expected. But the professor had been right: Calabrese had discovered something new. When he sprayed the plants with a diluted dose of the poison, as he had done mistakenly the first time, the plants thrived. By every measure—height, weight, root length—they did about 40 percent better than those that did not get Phosfon.      Thirty-six years later, in his office at the University of Massachusetts at Amherst, Calabrese tells the story with matter-of-fact assurance. Slight of build and gray of mop, standing hip deep among stacks of scholarly publications, he hardly looks like a revolutionary. He claims to have a "bland personality," and his owlish glasses and soft-spoken demeanor seem to bear this out. Yet his conclusions are as unflinching as they are controversial. Poisons that injure or kill at high doses can have the opposite effect at low doses, he says, and the paradox holds true for every conceivable measure of health—growth, fertility, life span, and immune and mental function. The effect is known as hormesis, from the Greek word for excite. "The implications," he says, "are enormous."     During the past decade, Calabrese has combed through tens of thousands of studies for examples of the effect, and he has found them in impressive numbers. Worms exposed to excessive heat, rats given a little dioxin, mice and humans exposed to low-level radiation—all have lived longer, in controlled experiments, than they would have without the toxins. Now Calabrese and a small but growing number of researchers worldwide are zeroing in on the biological basis for this effect. "If you really understood the master switch," he says, "it would become very powerful."     It also becomes scary. Using toxins to improve health sounds both irresponsible and suspiciously convenient for polluters. If a little dioxin is good for you, why bother to clean up the Hudson River? If a touch of arsenic can fend off cancer, why lower the allowable amount in drinking water, as the Environmental Protection Agency has urged? "This is one of the major awakenings we are going through," Calabrese says. "We really don't see any exceptions, and that's hard for people to deal with. But I have so much data—this is so overwhelmingly convincing—that I don't think anyone rational could deny that hormesis exists."  If any other researcher had chosen to champion hormesis, the theory might still be languishing in 19th-century medical tomes. What distinguishes Calabrese from a crank—what has earned him the respect of government regulators, scientific collaborators, and thousands of subscribers to his newsletter—is both his method and his background. "He is a mainstream toxicologist," says Donald Barnes, former staff director of the EPA science advisory board. "Everyone knows him. He is not a flake. And everyone respects the work he has done." It's hard to dismiss Calabrese as an apologist for polluters: He spent the better part of his career proving exactly how dangerous pollutants can be.     After those early experiments with peppermint, Calabrese published a paper and then shrugged off his small discovery—a paradox without explanation. When he arrived at Amherst in 1976, he set up a conventional toxicology lab. In the mid-1980s, he began to study carcinogens. The wisdom of the time held that carcinogens could cause cancer only after repeated exposures. Calabrese decided to take a closer look. Moving from the lab to the library, he devoted much of the next 15 years to reviewing 6,000 previous cancer studies. In more than two-thirds of the studies, he found evidence that a class of chemicals known as mutagens could cause cancer with a single exposure.     This was a style of research that would later serve him well with hormesis, and the results were nearly as controversial. Among the mutagens he had studied were food preservatives and other common substances—aflatoxins, for example, produced by molds. "Usually, in the beginning, people thought I was crazy," Calabrese says. "Industry was very upset." But he persevered, and his findings soon filtered into the mainstream. Around 1990 he told the state of Colorado that the EPA's limits for a toxic chemical leaching from an Army waste site were about a hundred times too lenient. After lengthy hearings in 1993, the state agreed. The Army faced an estimated cleanup cost of at least $7 million at that site alone—and it had 21,000 others to worry about.     It was intensely gratifying, Calabrese says, to realize the difference that one researcher's testimony could make. But by then he was already facing an even steeper challenge. In 1985 he had received an innocent-looking flyer in the mail that announced a conference on the stimulating effects of low-dose radiation. It may have mentioned hormesis, which he had never heard of before. He knows only that it sparked a memory. He called Leonard Sagan, an expert on radiation health effects, who was organizing the conference. He told Sagan he had seen a similar effect in peppermint plants 20 years before. "This was a transition for me to a phenomenon," he says, "not just an event."