One of the fathers of radiation genetics, Hermann Muller, was awarded the 1946 Nobel Prize in medicine for his discovery that X-rays induce genetic mutations.

This helped him call attention to his long-time concern over the dangers of atomic testing.

The expose

University of Massachusetts Amherst environmental toxicologist Edward Calabrese, whose career research shows that low doses of some chemicals and radiation are benign or even helpful, says he has uncovered evidence that Muller knowingly lied when he claimed in 1946 that there is no safe level of radiation exposure.

Calabrese's interpretation of this history is supported by letters and other materials he has retrieved, many from formerly classified files. He published key excerpts this month in Archives of Toxicology and Environmental and Molecular Mutagenesis.

Muller's intentions were good, Calabrese points out, but his decision not to mention key scientific evidence against his position has had a far-reaching impact on our approach to regulating radiation and chemical exposure, according to a University of Massachusetts Amherst press release.

Major experiment

Calabrese uncovered correspondence from November 1946 between Muller and Curt Stern at the University of Rochester about a major experiment that had recently evaluated fruit fly germ cell mutations in Stern's laboratory. It failed to support the linear dose-response model at low exposure levels, but in Muller's speech in Oslo a few weeks later he insisted there was “no escape from the conclusion that there is no threshold.”

To Calabrese, this amounts to deliberate concealment and he says Stern raised no objection.

Within a year after Muller and his group persuaded the NAS to accept the linear model for gonadal mutations, the practice was extrapolated to somatic cells and cancer. Twenty years later, NAS adopted the linear approach for chemicals.

Soon thereafter, the U.S. Environmental Protection Agency announced it would use the linear model for risk assessment, Calabrese points out. — Our Bureau