Is there a tonic in the toxin?
The idea that a small amount of a dangerous substance can stimulate the body's defenses isn't new--just think of vaccines. But try arguing that this same notion can apply to toxic environmental chemicals like arsenic and dioxins and you'll quickly get written off as either a quack or an apologist for polluters. Edward Calabrese argues just that, and somehow he has managed not to be demonized for his theory.
For years, this toxicologist has quietly worked at the University of Massachusetts-Amherst to bolster the credibility of the scientific theory known as "hormesis" --the idea that exposures to chemicals or radiation at low doses can have the opposite effect than at high doses. The field has been much maligned and confused with scientifically sketchy homeopathy since 1888, when a German pharmacologist named Hugo Schulz first noted that small amounts of poison encouraged the growth of yeast. Unlike homeopathy, however, which can involve solutions so dilute that they no longer contain any trace of the active substance, hormesis happens at low but real exposures that can often approximate the actual levels of toxins people encounter every day.
These low levels rarely get tested in the lab. That's because standard toxicology tests use much higher doses to quickly but roughly extrapolate what happens in the real world. Regulators currently assume that toxins either always pose some risk at any level or that there's a threshold below which toxins won't cause health problems. But while these assumptions are used to regulate everything from mercury to pesticides, Calabrese argues that they just don't reflect the paradoxical and sometimes beneficial effects seen at low doses in the lab. "The central pillar of toxicology is the dose response," he says. "I'm telling them that they got the most fundamental aspect of their field wrong."
Respect. By sticking to the science, Calabrese has brought hormesis to a previously unimagined level of respectability, with articles in top science journals and sessions at major toxicology meetings. And he's taking the logical next step--venturing out into the messy political world of environmental regulation, where passions run high. This past summer, in Toxicology and Applied Pharmacology , he proposed the heretical idea that government regulators switch to the hormesis model to assess how environmental chemicals affect humans' health.
That idea gives fits to environmental activists. They fear it might give regulators an excuse to let toxins linger in the environment. "I don't have a quarrel with Calabrese's science," says Gina Solomon of the Natural Resources Defense Council. "But I do have a quarrel with how this can be misused in the regulatory process." For Calabrese, however, it seems like the natural extension of what he's learned over the past two decades. "People had thought about hormesis in the past, but they were very ideological," he says. "I see hormesis as intellectually interesting."
Years before he ever heard the term "hormesis," back when he was a college student, Calabrese had his first brush with what was to become his calling. In one botany experiment, he noticed something weird: A chemical that was supposed to inhibit plant growth would, at low doses, spur the growth of peppermint. The oddity got stuck in the back of his mind as he finished his Ph.D., but the zeitgeist wasn't right for this idea. Rachel Carson's environmental classic Silent Spring had come out in 1962, the first Earth Day had been held in 1970, and the environmental sciences were booming.
advertisement
