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> Documents > RSH Data Docs > 1.2 > 1.2.2 > 1.2.2.1 Weapons Plant Workers References |
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"Low Level Revision 1 1.2.2 1.2.2.1 |
Dr.
Roger Berry, Westlakes Research Institute of the UK reports (1994) on 542
male workers, who had accumulated doses >500 mSv and up to ~2 Sv, by 1984, and an
overlapping group of 470 workers involved in fighting the Windscale fire in 1957 or
subsequent cleanup, with a collective occupational dose of ~180 person-Sv, that a
correlation was seen between dose and the incidence in peripheral blood lymphocyte
chromosomes. But, group mortality to date is not significantly different from the U.K.
national average, corrected for age, sex. and social class, and the slight excess of
observed over expected deaths is due not to cancer but to diseases of the circulatory,
system, with a slight deficit overall against expectation of deaths from cancer, due in
part to a large deficit of lung cancer deaths. The Windscale fire group show a similar
deficit of cancer deaths. Cancer incidence also shows rates below those expected in the
general population. "Thus, in a population of workers exposed during their occupation
over many years to radiation doses that would be considered unacceptable today, and
studied as a "bellwether" for predicting risks to current workers, there is
evidence at a cellular level of their having received that exposure, but as yet no
evidence of unpredicted harm." Shirley Fry, M.D., M.P.H., of ORISE, reports (1995) that in a population of 3,145 civilian employees at DOE facilities and the U.S. Navy’s Nuclear Reactor program who were exposed to >50 mSv (5 rem) in one year for 1943-1978, the individuals who were among the most highly exposed to radiation in the modern nuclear industry. There is no excess mortality due to cancers, and deficits for all-causes, and for digestive and circulatory causes of death. Cardis et al. of the International Agency for Research on Cancer, (IARC) report (1995) that the combined U.S., the UK and Canada, 95,673 workers (85.4% men) employed for >6 months with 2,124,526 person-years (PY) at risk and 15,825 deaths, 3,976 of which were due to cancer, "there is no evidence of an association between radiation dose and mortality from all causes or from all cancers". However, they claim that leukemia, excluding chronic lymphocytic leukemia (CLL) was significantly associated with dose (one-sided P value = 0.046; 119 deaths), and among the 31 other specific types of cancer , a significant association was observed only for multiple myeloma (one-sided P value = 0.037; 44 deaths), attributable primarily to the associations reported previously in the Hanford (U.S.) and Sellafield (UK) cohorts. A relative risk of 0.99 is reported for all cancers excluding leukemia and 1.22 for leukemia excluding CLL for a cumulative protracted dose of 100 mSv compared to 0 mSv. These estimates are lower than the linear estimates obtained from studies of atomic bomb survivors, but they are compatible with a range of possibilities, from a reduction of risk at low doses, to risks twice those on which current radiation protection recommendations are based. However: Wade Patterson, CHP and former editor of the Health Physics Journal, states (1996) that in the study by Cardis et al "Matanoski et al, 1991, ‘Health effects of low-level radiation in shipyard workers’, Report to DOE, 1991, the best dosimetry, and lack of confounding evidence, with best epidemiological population and study, was not included," quoting from the text: ‘The constant linear relative risk model used for deriving estimates for the workers...’. and ‘...the models derived by the BEIR V Committee for estimating risks of leukemia and respiratory, digestive and other cancers were applied to the data for the workers.’ "Thus the data used for risk estimates, comparisons, and analyses have been fitted to a curve with positive slope and origin at zero (the LNT)." And, "..from the text (referring to leukemia): ‘When the analyses were restricted to cumulative doses below 400 mSV and below 200 mSV, to assess the influence of death in the higher dose categories on the dose-response relationship, the association was no longer statistically significant...’ stating: "The data and analysis in this study do not indicate support for the LNT, contrary to the representations made by the authors and others." Also: Professor Emeritus Myron Pollycove, MD, of Laboratory Medicine and Radiology, UCSF, reports (1995) that the Cardis et al study: "...misrepresents dose-response data to report a ‘linear model’ result. The IARC report chooses to ignore data that shows lower risk, i.e., a risk decrement. First, …it chooses to ignore the most accurate data, the Nuclear Shipyard Worker Study compared to the early weapons facility workers with their questionable dosimetry and confounding factors. Then, in a population of 15,825 total deaths, IARC reports on 119 leukemia deaths, excluding non-radiogenic leukemia. The data show that there are 60 deaths observed with 62.0 expected for doses of less than 1 cSv, and there are 59 deaths observed with 57.0 expected for doses greater than 1.0 cSv… Clearly, there is no excess leukemia found in this data." Dr. Pollycove notes further on the IACR study that it "states explicitly… they applied (they presumed) the linear model across 11 dose categories, …and that ‘one-sided tests are presented throughout.’ This states that they effectively discount and ignore all negative data. Since only positive data are allowed to be considered, only the data from the three greater-than-expected dose groups are used, even though these dose groups are not even contiguous. Since the selected data are not significant, the IARC reports that it performs a Monte Carlo calculation on 5,000 trials (effectively multiplying the data by roughly a factor of 100) to ‘find’ that the results show a ‘significant’ linear dose-response ‘trend ‘.This ‘result’ was then the subject of a world-wide media campaign, reasonably reported even in Nuclear News, that the ‘linear model’ is confirmed. This report was widely distributed and accepted long before the data and analysis were published and available for review. IARC also reports that the 44 multiple myeloma deaths are similarly found ‘significant’, noting that this is ‘attributable primarily to the associations reported previously ... in the Hanford and Sellafield cohorts’ which indicates that they are aware ..that this ‘association’ is not found in other cohorts and is generally considered to be erroneous in the referenced studies, consistent with the weakness in the dosimetry and the confounding effects. In an April 1996 report to the NCRP on this study, Dr. Ethyl Gilbert (the second author) did not report that the study found support for the "linear model" in the data. However, the NCRP summary of the meeting explicitly attributed to Dr. Gilbert the conclusion that the IARC study had found confirming evidence of the ‘linear model’." Finally: Dr. Mario Schillaci of LANL states (1995) that in the IARC study, the dose distribution was skewed with 60% at <1 rem and only about 1% >50 rem. Excess relative risk for all cancers, excluding leukemia, was negative at -7 x 104 per rem. 90% CI (-39 to +30) x 104 per rem, which is consistent with zero risk. For leukemia, excluding CLL, the excess relative risk was 2.2 x 102 per rem, 90% CI (0.1 to 5.7) x 102 per rem, which is barely significant (the 95% CI overlaps zero). However, "The authors of this study give the relative risk (RR) for all leukemias except CL leukemia for 10-rem exposure as 1.22, which means that a person exposed to 10 rem of low-LET radiation over a working lifespan is 22 per cent more likely to die from non-CL leukemia than a similar, but unexposed worker. …the casual reader (would) infer that the data at dose levels around 10 rem actually show an effect. However, …the data presented for all non-CL leukemia mortality in 7 dose intervals, the last being greater than 40 rem, shows that for only the last dose interval is a positive effect observed. The risk factors quoted above are found by forcing a linear fit to all of the data; however, if the one data point for doses above 40 rem is excluded, the remaining 6 data points for doses below 40 rem show a flat response with dose (that is, no increasing risk with dose)." Drs. Valentin Hohyakov and Serve A. Romanov of the Public Health Ministry of the Russian Federation report (1994) on workers in Russia that lung cancer among 2346 workers in the ‘Mayak’ plutonium plant who were exposed to radiation, both externally and internally from incorporation of plutonium, shows that the groups with the lower doses have fewer cases of lung cancer deaths than expected, while the cohort with dose equivalent in excess of 4 Sv has 2.7 times the expected number of lung cancer deaths. |
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