To the Editor:

"Seeing Value in Poisons, a Toxicologist Takes On a Late Laureate" (The Chronicle, October 2) does a grave disservice to one of the 20th century's great scientists and to the public understanding of science. Although your account is certainly well intentioned, it fails to properly present the underlying scientific issues, the nature of the evidence used to ascertain the potential harm of nuclear radiation, and the way that evidence has been handled by various scientists since the original discovery, by Hermann J. Muller in 1926, that X-rays cause mutations.

The article begins with a narrative created by Edward Calabrese that was presented in a University of Massachusetts press release in September. The story, according to Mr. Calabrese, goes as follows: In the course of his research, Mr. Calabrese discovered a trove of letters and materials, "many from formerly classified files," which show that Muller and his colleague Curt Stern ignored data proving that a small amount of nuclear radiation exposure over an extended period was harmless. Mr. Calabrese alleges that Stern and Muller deliberately suppressed these findings and that in his influential Nobel Prize speech, Muller misrepresented the facts about nuclear radiation by claiming that such radiation posed a grave danger at any dose. Furthermore, Muller's continued repetition of this "lie" altered the entire history of the regulation of radiation and toxic chemicals in the United States. The result is that the public has been needlessly frightened and the government has wasted hundreds of billions of dollars in unnecessary cleanups.

While Mr. Calabrese's narrative is exciting, it is based on a combination of distortions, omissions, and facts that have been so divorced from their context that they end up totally inverting the truth. The real story is not difficult to reconstruct from the published record and the correspondence between Muller and Stern (which is neither classified nor difficult to find). It is as follows: At the end of September 1946, Stern wrote Muller thanking him for his editorial comments on a manuscript about the effects of low-level radiation. Stern also asked Muller if he'd have a look at another manuscript, which was yet to be typed, written by his colleague Ernst Caspari. Muller wrote back the next day saying that he'd be glad to see Caspari's manuscript. In early October, Stern wrote again, thanking Muller for agreeing to read the manuscript, which still hadn't been typed. On November 6, Stern wrote a third time, this time to report that the manuscript had at long last been typed and that he'd appreciate Muller's comments. Muller, who had been out of town, wrote back on November 12th and apologized for being too busy to respond immediately—as he was then preparing his Nobel address—but promised to try to read the manuscript before he left for Stockholm in early December. He added that he had glanced at the paper and could see that it was very important, and that it contained results "diametrically opposed to those which you and the others have obtained." He did not say, as you reported, that the results contradicted "his own previous understandings of the relationship between radiation and genetic mutations."

The prior results that Muller was referring to were those in Stern's unpublished manuscript that had been the subject of Stern's first letter. In that paper, Stern had shown that radiation even at extremely low doses, which were lower than had previously been tested, caused mutations. Furthermore the relationship between dose and mutation rate was linear. These results were totally consistent with many experiments that had been done over the previous 10 years. Caspari's data suggested that the situation was different at low doses in one crucial respect. Whereas at higher doses, it didn't matter whether the dose was given in one fell swoop or whether it was spread out over a month, Caspari's results showed that if low doses were spread out over 22 days, there was no increase in mutation rate at all. However, the experiment was an extremely difficult one to perform, and Caspari himself had doubts about his results. This is where the situation stood when Muller left for Stockholm.

Whether Muller had time to read Caspari's paper in detail before he gave his speech, we don't know, but it seems unlikely, as he didn't write back to Stern on Caspari's results. Furthermore, Muller would have been quite busy preparing his Nobel Prize address, which was delivered on December 12. In this speech, Muller repeated his long-held view that X-rays and other forms of radiation caused mutations, that the dose-response was linear, and that this was true for total doses (of gamma rays) as low as 400r delivered over 28 days. Based on this evidence, he asserted that there was "no escape from the conclusion that there is no threshold dose, and that individual mutations result from individual 'hits.'"

Eventually, Caspari retested his results, which were then reported in a Genetics article published with Stern that appeared in early 1948. In this paper, Stern and Caspari discussed the special difficulties in conducting experiments at such low doses spread out over many days. Nonetheless, in no uncertain terms, the Caspari-Stern paper reported that there was no increase in mutation rate and acknowledged that this result was at odds with Stern and others' earlier findings. For this reason, it is difficult to imagine what exactly Professor Calabrese had in mind when he accused Stern and Muller of covering up Caspari's results.

After publishing this paper, Caspari, who had had enough of the tedious work that was required to compute mutation rates in flies, went on to greener pastures, leaving to other researchers the question of whether flies exposed to low-dosage radiation over an extended period of time show an increased mutation rate. Meanwhile researchers turned their attention to the study of radiation effects on mice and other animals. In the case of humans, an enormous body of data was analyzed by John Gofman, who established the Biomedical Research Division for the Lawrence Livermore National Laboratory, unambiguously re-establishing that there was no safe level of radiation. In light of the proliferation of nuclear reactors in subsequent years, and the two major accidents at Chernobyl and Fukushima, the public would be well advised to be afraid, to fear for themselves as well as the health of future generations.

James Schwartz
Brookline, Mass.

Mr. Schwartz is the author of In Pursuit of the Gene: From Darwin to DNA.