Way ze ! §¥/ New A-Bomb Studies Alter Radiation Estimates eee ween [Scinel] tut | —-News and Comment numb: ered | und ta radial the au As The basis of 15 years of radiation research may bein error; data able u Nagits radiation toxicity may be understated sparked interest in the issue. Kerr, Kaul, and Jess Marcum of Research and Development Associules in Santa Monica, California, huve been funded by the Defense Nuclear Agency to explore the problem and check some ofthe old as- sumptions which have not yet been reexamined. Although they differ in some of the details they stress. all of these scientists agree that the accepted figures for high LET (neutron) radiation at Hiroshima are grossly overstated. For eaumple, the neutron radiation at a distance of 1180 meters from the epicenter of the blast appears to have been overestimated by a “The terms “low LEP and “heh LEE dor linear energy transfer) reter to the physical quality of the ray. Low LET radtation loses relatively little energy as it travels along ity course, and includes electrons, gamma rays. and \-rays. Hieh (T radtafon loses enerey more rapidly as i travels. and includes beams of deutroas und protons QO 7 radiit increu - presto puller ~ Some of the most impurtant data on the effects of nuclear radiation on humans may be wrong, according to new research being done ut the Lawrence Livermore weapons laboratory in Caliltfurnia and the Ouk Ridge National Laboratory in Tennessee, The new findings are far from welcome, as one consultant in this work says. for all the revisions “ure moving in the wrong direcuon’’—a direction that will worry the advocates of nuclear power. Government physicists have recalculated the data on the radtation fields created by the atumic blasts at Hiroshima und Nazusuki and produced some unexpected results. Their staustics showthat most of the cancer cuused by those bombs came trom low LEY gumma rays.” suggesting that this common type of radiation is mure hazardous than had been assumed before. The impetus fur the revision comes primarily from Livermore, where physicisis William Loewe and Edgar Mendelsohn lust year used a computer to reconStruct the two explosions. Their findings ure being checked and complemented by a group at Oak Ridge led by George Kerr. He began work on a similar project in 1977, shelved it, and then returned to the task in eurnest when Loewe's data became known. Dean Kaul of Science Applications, Inc., in Chicago also carried out some early calculations that tm reveul of rad relath tom! : ral ba. a prop morta U.S. Air Farce Did it produce neutrons or mostly gamma rays? Duplicate of the bomb thet hit Hirostiare factor of 6 to TQ) Since the cffeels on human health remain the sume, one must conclude that the gammarays were More toxic than had been thought. If this research proves correct—and it has survived a few peer challenges alread y—it will necessitate the rewriting of many basic documents on the hazards of radiation, including the chief attempt to define such risks published tn 1980 by the National Academyof Sciences. That study. the work of the Committee on the Biological Effects of lonizing Radiation (the BEIR report), wus fraught with controversy On this very question. Although much of the BEIR report was released to the press in May .1979, the Academy decided to recall and rewrite it because of dissension umong the authors. Some of them, led by Columbia University biophysicist Harald Rossi. argued that the paper overstated the cancer-cuusing effects of low LET radiation. Their arguments leaned heavily on Jupanese data and particularly oa the thesis that many of the cuncers in Hiroshima were produced by high LET neutron radiation. Using the old Hiroshinia radiation data us evidence. Rossi argued that the BEIR committee should lower the cancer risk estimates published tn an cartier BEIR report in 1972. Instead, the commitice ruised the risk estimates. Rossi conmsidered this an alarmist move and withdrew his support from the ducument. In the end. the Academy felt compelled to write a report that effectively split the difference between Rossi's port of view and that of his chief adversary. tne committee chaurman. Edward Radford. an ooo SU7S XPOS 2 OOUSOD Odeo Cape resdl [Ya; eS epidemiologist at the Gniversity of Pittsburgh. The risk estimates in the final report of July 1980 were not as high as Radlord argued they should be nor even aus high as those in the 1972 report. Neither Radford nor Rossi endursed the document. Rosst concedes that the Livermore calculations muy do away with the evidence for his theory that neuirons were responsible for the high cancer incidence in Hiroshima. But he does nol expect to alter his general view that the hazurds of radiation are exuggerated. Radford, in contrast, says the new Hiroshima dula vindicate his position and invalidate Rossis. Furthermore, Radford considers the BEIR 1980 report obsolete and expects that the probabilities it gives for the risk of dying of cancer after exposure to gamma radiation will be doubled. Likewise, he thinks the probabilities for contracting any form of cancer after irradialion wil be quadrupted. The importance of the newresearch is that ii conipletely changes the scheme of radiation doses that people ure supposed to have received tn Jupan. particularly in Hiroshima. Untill now, it was thought that the Hiroshima blast wis unique in that it produced a large field of fast neutrons, a high LET form of radiation. Neutron radition is considered more diuigerous than low LEV radiation, a culegory that includes X-rays, electrons, and gama rays. [ts singidia presence in Hiroshima wus said to make the cancer risk found there anomalous Most ofthe radiation people encounter is not of this kind. The wastes from nuclear reactors, for eNaieple. entil gamma rays. Thus, a Ne IENG $OON a wrap ae ier, Mm of ink is thal uccuri Hiros! asus to low saypl like. recale But n to Ser ablyul ma ra Ruc view. roshul distri tific ¢ reporl mora tificut readin even. ford | much death theor of the He 1s may rest. oT healt! thers Autat und c Nuch the re firm serib con new hand Ross matt shim . Ad