Work on How Low Doses of Radiation Effect Health Wins Marie Curie Prize

Edward Calabrese, a professor in the School of Public Health and Health Sciences at the University of Massachusetts Amherst, has been awarded the Marie Curie Prize for “outstanding achievements in research on the effects of low and very low doses of ionizing radiation on human health and biotopes.”

At an international conference this week at UMass Amherst, André Maïsseu, president of the Paris-based World Council of Nuclear Workers, announced that Calabrese is the council’s 2009 Curie Prize winner. Maïsseu saluted Calabrese during the annual meeting of the International Dose-Response Society, of which Calabrese, an environmental toxicologist, is a founder and current director. Maïsseu said the prize recognizes an entire body of research that has improved scientific knowledge of low-dose ionizing radiation effects on human beings and biological communities. A formal award ceremony will be held in Rio de Janeiro, Brazil, in September.

While Calabrese is the foremost expert in the world on a chemical dose-response phenomenon known as hormesis, he has done little dose-response work with ionizing radiation, he observes. However, he feels deeply honored by the council’s recognition. “I accept that I’m being given credit for bridging the gap between chemical hormesis and ionizing radiation,” he says, “and I do believe there is evidence to bridge it. What I have urged all along is for mainstream science to see hormesis as a basic biological principle.”

Hormesis describes the fact that low doses of some chemicals are stimulative or promote growth but higher doses are toxic or inhibit growth, for example. The Marie Curie Prize winner, who joined the UMass Amherst faculty in 1976, says, “We need to conduct the research―which has been long neglected―to understand hormesis more fully, with all its implications.”

The theory’s proponents suggest that low doses of minerals in multivitamin pills such as chromium and selenium, for example, boost health not because they provide required nutrients but because low doses of many toxins stimulate biological systems with beneficial mild stress, while higher doses are toxic. By contrast, the prevailing linear threshold model of toxin behavior says the absence of harmful effects below the threshold assumes there are no effects relevant to health.

Calabrese and colleagues’ work on chemical hormesis sparked vigorous scientific debate and a special section in the journal, Science, in 1989. Challenged to subject hormesis experiments to more rigorous statistical standards, Calabrese and his longtime UMass Amherst collaborator, Linda Baldwin, created a database of 21,000 papers. In 2003, they reported in a ground-breaking paper that the low-dose stimulatory effect of chemicals is typically about 40 percent enhanced growth, for example.

“It was a coming-out party for hormesis,” Calabrese recalls. “We made a credible case and we did it by following the scientific rules of the game,” he says of their work over the past 30 years. By contrast, he says, the two leading risk assessment models used by the Environmental Protection Agency and the Food and Drug Administration have been imposed on society and the scientific community without being vetted or validated.

Everyday implications of hormesis for risk assessment are significant. If chemical hormesis is a basic biological principle, Calabrese says, society is needlessly over-regulating the environment to protect against low exposures that are not dangerous, and we’re missing possible benefits. “The traditional threshold model is not very good at explaining or accounting for data that’s below the toxic threshold, and that’s where we live. But hormesis is quite good at that.”

Mark Mattson, chief of the Laboratory of Neurosciences at the National Institute on Aging, one of Calabrese’s past co-authors, agrees that the findings for which Calabrese is being recognized with the Marie Curie Prize “have major implications for public health policy regarding environmental ‘toxins,’ for the design of biomedical studies, and for the discovery of new therapeutic interventions for a range of diseases.”

Mattson adds that the UMass Amherst research clearly reveals that “hormesis as a widespread feature of biological systems (cells, tissues, organisms and populations) that was previously either unrecognized or ignored by scientists in the fields of biology, biomedical research and toxicology. Calabrese and colleagues have shown that biological systems very often respond adaptively to low amounts of toxins and other stresses (radiation, heat, etc.) so as to increase their resistance to more severe stress and disease.”

Maïsseu says it’s unfortunate that most research on ionizing radiation conducted since nuclear weapons were developed has focused on its harmfulness. This has prevented valuable work on possible beneficial low-dose effects, including adaption and repair mechanisms, he feels. Further, anti-hormesis prejudice has deprived the scientific community of fundamental knowledge which might be uncovered, and which is needed to pursue the fight against the different forms of cancer, Maïsseu adds.

He therefore salutes Calabrese’s “courageous opposition to this indefensible position with regard to scientific research.” Recalling the famous statement by the 15th century toxicologist, Paracelsus, that all substances are poison and only dose makes a poison, Maïsseu adds, “Calabrese dared to undertake work making it possible to correctly appreciate the relationship between dose and effect in many areas of toxicology and biology, and to highlight numerous examples of the hormesis phenomenon.”