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[cdn-nucl-l] Critique of NCRP 136, a question of ethics?
A Critique of NCRP Report No. 136 "Evaluation of the linear-nonthreshold
dose-response model for ionizing radiation."
by John Cameron (e-mail: jrcamero@facstaff.wisc.edu)
NCRP Report No. 136 cites the nuclear shipyard worker study (NSWS)-the best
epidemiological study of radiation workers ever done. (Matanoski 1991) The
data in that reference alone is more than sufficient to reject the
conclusions of this report. The report also references the British
radiologists study (Smith and Doll 1981). That study provides confirmatory
data to the NSWS. NCRP Report No. 136 report does not present data from
either of these two important studies.
The NSWS has yet to be published in a scientific journal. Normally,
unpublished reports are not considered to have been "peer reviewed". The
NSWS had excellent peer review during its eight-year duration. The DOE
contract provided for peer review twice a year by a panel of eight
scientists with expertise relevant to the research. Appendix 2 of the final
NSWS report states: "The Technical Advisory Panel (TAP) was formed in 1980
as a standing committee of experts who would provide objective advice to the
project staff on a continuing basis. In selecting its members, it was
important for each [TAP member] to have had personal research experience
with some of the problems related to the Shipyard Study. Disciplines which
we believed to be important and which were included in the group are:
radiation biology and radiation physics, medicine, genetics, industrial
hygiene, epidemiology and biostatistics."
Scientists who served as members of TAP were Dr. Arthur Upton, (chair);
Gilbert Beebe, John Cameron (the author of this critique), Carter Dennison
(who resigned in 1983), Merril Eisenbud, Philip Enterline, Philip Sartwell
and Roy Shore. TAP met twice a year to review data, question the scientific
staff and make suggestions. Early in 1988, TAP approved the draft of the
final NSWS report.
Note that Dr. Arthur Upton, chair of NCRP SC 1-6 which wrote NCRP Report No.
136 was also the chair of the Technical Advisory Panel and Dr. Roy Shore,
another member of NCRP SC 1-6 was also a member of TAP. I cannot believe
that the significant beneficial effects of low dose rate radiation shown in
the NSWS final report were not well known to these two scientists. I must
conclude that the beneficial results of the NSWS were intentionally ignored
by these two NCRP SC 1-6 committee members.
The draft of the final report of the NSWS was approved by TAP early in 1988
at the conclusion of the study. For reasons which have never been explained,
the final NSWS report was not submitted to DOE until the fall of 1991. Even
more mysterious is why the results of this important $10 million study have
not been published more 13 years after its completion.
Presumably all of the TAP members agreed with the summary in the final NSWS
report (p. 393) which states: "The shipyard nuclear worker population
represents a large number of individuals exposed to low documented [doses]
of radiation. They receive this radiation almost exclusively from gamma rays
due to the decay of cobalt-60. Within the [shipyard] population there are
comparable groups of workers exposed to negligible or no radiation at their
shipyard jobs but who engage in similar work. Therefore this is an ideal
population in which to examine the risks of ionizing radiation in which
confounding variables can be controlled. ."
There is no doubt that this was the best epidemiological study of radiation
workers ever done. The health of 28,000 nuclear shipyard workers with the
highest cumulative doses (> 5 mSv) was compared with the health of 32,500
shipyard workers with the same jobs and same ages. In addition the exposed
group had good dosimetry of their occupational doses. I estimate that the
average cumulative dose of the study group was roughly equal to about five
times their annual background gamma ray dose. This dose is comparable to
the dose which most residents in the U.S. mountain states get routinely.
The NSWS final report neglected to compare the total cancer mortality of
the nuclear workers and the controls. Data in the final report indicate that
the cancer mortality of the nuclear workers was 4 std. dev. lower than that
of the controls. (p< 0.001) (Pollycove, private communication). I am sure
that if the nuclear workers had had significantly more cancer mortality, it
would have been taken as evidence of the carcinogenic risk of low dose rate
radiation. It seems reasonable to assume that the significantly lower cancer
death rates of the nuclear workers is strong evidence that low dose rate
radiation stimulated their immune systems.
The death rates from all causes of the nuclear workers was 24% lower than
their age-matched and job-matched controls. This is 16 std. dev. or p<10-16.
This statistical power leaves little doubt that low dose rate radiation
stimulates the immune system. This surprising result was not mentioned in
the narrative portion of the the final report of the NSWS in the fall of
1991 nor is it mentioned in NCRP Report No. 136.
The nuclear shipyard worker study was to examine "risks" rather than "health
effects". The final report concludes correctly, "The [exposed] population
does not show any risk which can be clearly associated with radiation
exposure in the current analysis." It seems unethical to me for the
narrative portion of the NSWS final report not to mention the apparent
health benefits to nuclear workers.
Although the study involved radiation, the NSWS final summary does not give
cumulative dose in "rem-years". An estimate can be made from Table 3.1.C1 in
the final report. Doses to the NW>0.5 group were divided into four dose
categories. A worker may contribute to each of the four groups. A rough
estimate from that table suggests that the NW>0.5 group, had average doses
5 to 10 times their cumulative dose from background (excluding radon
progeny.) That is, their occupational dose was comparable to background
doses received by people living in mountain states. The lower cancer
mortality of the nuclear workers is consistent with the 25% lower cancer
death rate in three U.S. mountain states compared to the cancer death rates
in three U.S. Gulf States. Background radiation is about three times higher
in the mountain states than in the Gulf States. (Jagger 1998).
The improved health of the nuclear workers supports the hypothesis that a
moderate dose rate of radiation stimulates the immune system. (Cameron 2001)
If the aim of the NSWS had been to look for health benefits of ionizing
radiation, it would have been a huge success. As a study to find radiation
risks, it was an abysmal failure. This may explain why the study has yet to
be published. I published a brief summary of the results, shortly after the
final report was submitted. (Cameron 1992).
The reader may think that the nuclear shipyard worker study is contradicted
by other epidemiological studies. I know of no contradictory studies. The
British radiologists study--(Smith and Doll 1981)--supports the hypothesis
that low dose rate radiation stimulates the immune system. That study also
looked at the cancer death rate as well as the death rate from all causes.
It gives results consistent with NSWS. (Table 1.) Radiologists in the study
were divided into two groups-those who joined a radiological society before
1921 and those who joined such a society after 1920. The dividing date was
chosen because the British x-ray safety committee became active about 1920.
There was a need for the committee as data in Table 1 indicate. The large
radiation exposures to early radiologists significantly increased their
cancer death rate compared to three control groups of men in England and
Wales.
Despite the large occupational exposure to the early radiologists, their
death rate from other causes decreased. That is, there was no statistical
evidence of a decrease in longevity compared to the three control groups.
This suggests that radiation stimulation of their immune systems canceled
the radiation induced cancer deaths.
There can be little doubt that the British x-ray safety committee did its
work well. Note the great decrease in cancer death rate after 1920. More
importantly, the study provides strong support for radiation stimulation of
the immune system. Note the statistically significant decrease in deaths
from all causes. The probability of this health improvement being accidental
is generally lower that 0.001.
Chap. 9 of the report criticizes the weak power of epidemiological
radiation studies to detect increased cancer from low dose rate radiation.
These criticisms are not relevant to the statistically strong data found in
the NSWS and British radiologists study.
The facts presented above call for an investigation of why NCRP SC 1-6
produced such a biased conclusion on the validity of the LNT model of
radiation risk when good human studies referenced in their report contradict
their conclusion. NCRP SC 1-6 ignored important relevant data which clearly
contradict the LNT model.
------------------------------
References:
Cameron, J.R. The Good News About Low Level Radiation Exposure Health
Physics Society Newsletter Feb pp. 9-11(1992)
Cameron, J.R. Is radiation an essential trace energy? Physics and Society
Oct. 2001 (in press)
Jagger, J Natural Background Radiation and Cancer Death in Rocky Mountain
and Gulf Coast States Health Physics Oct. pp 428-434 (1998)
Matanoski G: Health effects of low-level radiation in shipyard workers final
report. 471 pages Baltimore, MD, DOE DE-AC02-79 EV10095, (1991)
Pollycove, M. 2000 private communication.
Smith PG, Doll R. Mortality from all causes among British Radiologists Br. J
Radiol 1981; 54: pp 187-194 (1981)
------------------------
Table 1 Mortality of British Radiologists 1900 to 1980
Deaths of British radiologists were compared to three groups:
A-All men in England and Wales; B-All men in social class I; C-All male
medical practitioners.
A total of 1338 radiologists were divided into two groups:
"Before 1921": All British physicians who joined the British Institute of
Radiology or the Royal College of Radiologists before 1921 and
"After 1920": All British physicians who joined either society after 1920
(From Smith PG, Doll R. 1981)
O/E = OBSERVED/EXPECTED DEATHS
Results:
BEFORE 1921
AFTER 1920 .
GROUP DEATHS O/E DEATHS
O/E
DEATH FROM A 0.95
0.76***
ALL CAUSES B 319 1.04 411
0.89*
C
0.97 0.87**
----------------------------------------------------------------------------
-----------------------
DEATH FROM A 1.26*
0.63***
ALL CANCERS B 62 1.44** 72
0.79*
C
1.75*** 1.05
----------------------------------------------------------------------------
-----------------------
DEATH FROM A 0.95*
0.79***
OTHER CAUSES B 257 0.97 339
0.92
C
0.88* 0.84**
----------------------------------------------------------------------------
---------------------
STATISTICAL SIGNIFICANCE: * p<0.05, ** p< 0.01, *** p< 0.001
----- Original Message -----
From: "John Cameron" <jrcamero@facstaff.wisc.edu>
To: <rad-sci-l@ans.ep.wisc.edu>
Sent: Monday, August 06, 2001 8:17 PM
Subject: [rad-sci-l] Revised draft Critique of NCRP 136 for Health Physics
> Dear Colleagues, It seems to me it is worth publishing this short
> article in Health Physics (after it is polished up). Please send me
> your thoughts and suggestions.
> My right knee is improving. I hope to retire my crutches this
> weekend for a few months. Surgery on my left knee is scheduled on
> Oct. 18.
> Best wishes, John
----------------------------------------------------------------------------
----
> --
> John R. Cameron (jrcamero@facstaff.wisc.edu)
> PO Box 405, Lone Rock,WI 53556
> (608) 583-2160; Fax (608) 583-2269
> until about Nov. 30, 2001
>
> 2678 SW 14th St. Gainesville, FL 32608
> (352) 371-9865 Fax (352) 371-9866
> (December to early May)