Comment on “Health effects from radiation” Alternative conclusions about cancer rish from low doses of ionizing radiation By Rudi H. Nussbaum
In a recent ES&T article, Robert E. Alexander states: “The most significant problem highlighted by Three Mile Island and Chernobyl may be the very real possibility that important decisions to be made about nuclear electric power could have a speculative technical basis” (ES&Z “Views,” February 1988, pp. 144-45). I fully agree with him, but I would extend this real possibility to those decisions that already have been made by government agencies and industry in the past. The author correctly pinpoints the basic technical question underlying all nuclear safety discussions. Safety or environmental leakage tolerances must always be based on estimates of health risks from radiation exposures, be they related to nuclear weapons manufacture or tests, the operation of nuclear reactors for electric energy, or the longterm storage of nuclear waste. The scientific basis for such estimates of health effects is the province of the statisticalmedical science of epidemiology. In this context tcw I agree with Alexander when he states: “In my opinion there is very limited place for conjecture and speculation in science.” Unfortunately, Alexander then DTOceeds to devotd the body of his ariicle to statements about results from radiation health studies at low doses without qualifying these statements as conjectures based on speculative analysis of obsolete data. Most disturbing, the author completely ignores the grossly differing results from the most recent pertinent data. The authoritative position of the author could easily mislead the reader into accepting Alexander’s judgment as solidly established scientific evidence regarding our knowledge of health effects from lowdose exposures. The purpose of my comment is to cite recent studies that present contrasting conclusions about cancer risks from low doses of ionizing radiation. This critical comment has equally been in740 Environ. Sci. Technoi., Mi. 22.No. 7. 1988
causes of death, which mask the can-
cers (1-3).
Assigning new doses Moreover, during the past decade reevaluationsof the models used to calculate the survivors’ assigned doses revealed gross errors. A substantial reassignment of persons to different dose ranges is now required-thus a complete revamping of the survivor study has been started. For example, in the Hiroshima combined dose categories under IO rad-the most important dose range for direct evaluation of lowdose risks-l7% of the initial 44,141 persons have been excluded from the Rudi H.Nussbaum original subcohort for lack of complete information about the circumstances of their whereabouts at the time of the spired by Alexander’s concern for the bombing; 14% of the remaining 36,662 “very real possibility” that decisions to persons have been reassigned to adjabe made about nuclear technology cent dose ranges. The corresponding “could have a speculative technical ba- figures for Nagaski are 15% excluded sis.” Alexander reports that radiation and 25% reassigned. For the entire risk estimates at lowdose levels are 1950-1985LSScohort, 17% ofallcanprimarily based on the Life Span Study cer cases had to be removed from the (US)of 54,ooO survivors of the Hiro- original study (4). An unbiased review of known health shima-Nagasaki bombing; the radiation doses of these survivors were esti- effects from radiation would have to mated on the basis of their distance to point out that current cancer risk estimates by official bodies-such as the the hypocenter. In fact, official lowdose risk esti- International Commission on Radiation mates currently are based on cancer sta- Protection (ICRP) or the United Natistics. comviled from 1950 to 1974. of tions Scientific Committee on the Efabout’ lOO~O00Hiroshima-Nagasaki fects of Atomic Radiation-are hyposurvivors and on highly speculative thetical extrapolations from a base of extrapolations from clearly observed obsolete data. Risk estimates by these effects at high doses to formerly unde- organizations do not take into account tectable effects at low doses. Bearing in the latest cancer statistics at the lowmind that the choice of a linear or lin- dose ranges or the revised dosimetry, ear-quadratic, dose-effect relationship yet such estimates remain the foundaused for extrapolation is based on an tion of current official radiation protecuntested hypothesis, the reliability of tion standards. These are the risk estilowdose risk factors is brther affected mates that have been used to project the by reient statistical evidence. This evi- 28,000 extra cancer deaths as a result dence shows that the recorded high- of the Chernobyl disaster, a number dose cancer effects among the survi- that Alexander calls “alarming and vors may lead t o a substantial misleading.” underestimate of the rate of true cancer New radiation risk calculations based induction at those doses as a conseon the latest statistics and the new doquence of competing dose-related simetry models are presumably being W13936x1(18109221.50/0
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made by various official commissions. But statements by experts from the nuclear establishment, such as those by Alexander, will continue to undermine the credibility of expected revised conclusions about cancer risks at low doses until the complete basis of dose recalculations (i.e., the complete set of raw data) becomes available for scrutiny to scientists outside such highly secretive laboratories as Livermore, Oak Ridge, and the Radiation Effects Research Foundation (RERF) in Hiroshima. RERF is a public US.-Japanese venture under the U.S. National Academy of Sciences and the Japanese Ministry of Health and Welfare. But the detailed and specific requests by outside scientists for access to primary statistical data (e.g., noncancer deaths) have never been honored. Yet risk estimates for radiation-induced cancers depend critically on the presence or absence of confounding effects of competing radiation-related causes of death among the survivor populations (1-3).
Updating old data A specific illustration of a credibility gap on the subject of radiation health effects is Alexander’s statement that the A-bomb survivor study “provides statistically sound information [about cancer risks] only for doses exceeding 10 rads.” This statement is as obsolete today as the official risk factors that led to the estimate of 28,000 additional cancer fatalities from the Chernobyl fallout. Undermining the author’s credibility even further is his statement that if “true” lower risk factors-valid at lower total doses and lower dose rates, and appropriate for most of the fallout victims-had been used instead of the official risk factors, the expected number of extra cancer victims from fallout would be reduced to 410. This comforting “theoretical” number is presented without justification by any applicable radiation epidemiological study. Alexander merely presents a statement of personal belief in a strongly concave dose-effect relationship at low doses and low dose rates without stating so explicitly. This type of relationship would indeed predict a much smaller increase in risk per unit dose (Le., a negligible slope of the dose-effect curve) at low doses than the linear extrapolation from high-dose effects used by the ICRP What about Alexander’s statement that we have no reliable information about the cancer-inducing effects of low levels of radiation? The current facts are as follows: In a recent summary of cancer statistics among the A-bomb survivors, RERF scientists updated the data to 1982 and found a 32% increase in cancer deaths, mostly among those
in the low-dose categories, compared with the 1950-1974 data on which current ICRP risk estimates are based. This sizable increase, particularly at the low-dose levels, is a direct consequence of the well-known long latency periods for cancers. For the first time since the study began in 1950, the group of about 66,000 survivors from Hiroshima and Nagaski with external doses below 10 rads does show a statistically significant excess of cancer mortality (4). (The above doses were analyzed using the old T65DR dosimetry, the method for calculating individual doses of survivors in 1965. The method was modified in 1980.)
Radiation cancer risks By comparing the cancer rate for the dose category (1-9 rad) with that of the 10-49 rad group, and using a linear interpolation, one can estimate the Abomb survivors’ radiation-related lifetime cancer risk to be about 35 excess fatal cancers per 10,000 person-rem for effective organ doses in the range 1-10 rem, neglecting a likely 23% underreporting of cancers on survivors’ death certificates (4, 5). A person-rem is a population dose (Le., the number of persons times their biologically effective tissue dose in rem). The corresponding SI unit is the person-Sv, which equals 100 person-rem. These risk estimates must be compared with the official ICRP value of about 1.25 cancer fatalities per 10,000 person-rem, which was derived from earlier RERF statistics that cover 1950-1974 data and used the same 1965 dosimetry. Again, this official ICRP value represents the now-obsolete lifetime risk value for fatal cancers on which currently adopted radiation protection standards are based; it also is the basis for the “alarming” prediction of 28,000 Chernobyl cancer victims, as mentioned by Alexander. The updated cancer risk estimates for the low-dose range from the 1950-1982 A-bomb survivor study (4, 5) yield instead a prediction of about 800,000 to more than 950,000 excess fallout-related cancer victims over the lifetime of the affected populations in Europe and the Soviet Union (if one includes the factor 1.23 for missed cancer deaths among Abomb survivors and if the average population dose estimates are reliable). Although these truly disturbing numbers take into account the cancer mortality rate among the A-bomb survivors through 1982, they still are based on the recently discredited T65DR dose assignments for the A-bomb survivors. In the 1987 RERF report, which includes three more years (1983-1985) of survivor cancer statistics and incorporates the newly revised (DS86) dosime-
try. Preston and Pierce, using a linear dose-effect model up to the highest dose range, arrived at a radiation cancer risk of about 17 fatalities per 10,000 person-rem, assuming the nowpreferred value RBE = 1 for neutrons (6). This updated cancer risk value from the A-bomb study yields an estimate of 380,000 future excess cancers as a result of the Chernobyl fallout. Although these estimates, based on the most reliable data, are lower, they still must be recognized as truly alarming. Moreover, nothing has been said about unavoidable long-term genetic damage. Thus the designation “catastrophic nuclear accident” used by Christopher Flavin in this journal (3, which Alexander calls “misleading,” is surely justified. On the contrary, any attempts to deliberately minimize the magnitude of the Chernobyl accident and its major ramifications for large populations in the Soviet Union and Europe by misrepresenting current scientific evidence is disingenuous (8, 9). As is true with the asbestos, the tobacco, or the fluorocarbon industries, nothing but the best available scientific evidence-even if controversial or most unwelcome7must guide all public policy decisions about nuclear technology in a society of free and responsible citizens.
References (1) Stewart, A. M.; Kneale, G. Health Phys. in press. (2) Alvarez, R. Bull. At. Sci. 1984, 40(8), 26-28. (3) Nussbaum, R. H. Bull. At. Sci. 1985, 41(7). 68-71. (4) ‘Preston, D. L. et al. Radiat. Res. 1987, 111, 151-78. (5) Proc. International Colloquium on Health Effects o f Low Level Radiation (Feb. 1988) in-Munsier (FRG); Springer-Verlag: Berlin-Heidelberg, in press. (6) “Risk Estimates in the Atomic Bomb Survivors’’; Technical Report RERF TR 9-87, 1987; Radiation Effects Research Foundation, Hiroshima, Japan (Caveat: The reduction factors for these cancer risks, subsequently applied by the authors of the re ort [p. 351, have no valid scientific justiEcation.) (7) Flavin, C. H . Environ. Sci. Technol. 1987921, 624-25, (8) Wilson, R. Issues in Science and TechnoEology. Fall 1986, 21-29. (9) Goldman, M. Science 1987, 236, 658.
Rudi H. Nussbaum, professor emeritus of physics and former radiation safe0 oflcer at Portland State UniversiQ, independently analyzed recent Hiroshima-Nagasaki cancer statistics and reported his conclusions this year at the International Colloquium on Health Effects of Low Level Radiation (West Germany). He is the local coordinator of radiation-epidemiological studies of low-dose eflects on human health through the PSU Environmental Sciences and Resources Program. Environ. Sci. Technol., Vol. 22, No. 7, 1988 747
