The Five Most Important Conclusions of This Book
Before summarizing the five key findings of this book, we need to specify what we mean by a few terms.
The term "radiation" in the title of this book refers to X-rays, gamma rays, and beta particles -- in other words, to ionizing radiation in the low-LET class (LET, or Linear Energy Transfer). The very special nature of ionizing radiation and of Linear Energy Transfer, with respect to biological injury, is
The term "low-dose exposure" in this field refers to internal organ-doses below about 20 centi-grays (a centi-gray or cGy is the same as a rad). The estimates derived in this book, of cancer-risk per centi-gray, apply to the dose-range between zero and five centi-grays of internal organ-dose. And our risk-estimates apply to received instantaneously (acutely).
Our range of zero to five centi-grays is the applicable low-dose range for most environmental, occupational, medical (diagnostic), and dental exposures.
The term "an independent analysis" in the title refers to independence from the radiation community. We use the term "radiation community" in this book to mean all the industries, professions, and governments engaged in activities which cause exposure to ionizing radiation, plus the individuals who regard their jobs, their research grants, or their personal advancement as dependent on such sources.
The leading members of the radiation community are (A) governments -- which sponsor civilian and/or military uses of nuclear energy, and sponsor the overwhelming share of all research on radiation's health-hazards -- plus (B) the nuclear electric industry and (C) the professions of nuclear medicine and radiology.
The Prominent Radiation Committees :
The radiation community's most prominent committees on health effects are four: BEIR, ICRP, NCRP, and UNSCEAR, and they each issue sporadic reports. Their individual members receive recognition in our Chapter 37. BEIR and NCRP are American committees, and ICRP and UNSCEAR are international. Radiations, and the BEIR Committee is organized under the auspices of the National Research Council of the National Academy of Sciences, at the request and expense of the federal government, now via its Office of Science and Technology Policy, Committee on Interagency Radiation Research and Policy Coordination. NCRP stands for National Council on Radiation Protection, and the NCRP is funded by the radiation community too.
BEIR stands for Biological Effects of Ionizing ICRP stands for International Commission on Radiological Protection. Founded in 1928 by radiologists, it continues to select its own members from various segments of the radiation community. UNSCEAR stands for United Nations Scientific Committee on Effects of Atomic Radiation, and it reports to the U.N. General Assembly.
The Atomic-Bomb Survivors of Hiroshima and Nagasaki :
Of the five key findings in this book, the first three are directly related to the on-going Lifespan Study of 91,231 atomic-bomb survivors. Contrary to common assumption, the A-Bomb Study is primarily a low-dose study; very few of the survivors at Hiroshima and Nagasaki received high doses. Over half of the 91,231 survivors in this study are still alive, so the Lifespan Study is far from completed.
The A-Bomb Study is maintained in Hiroshima by the Radiation Effects Research Foundation (RERF), which is sponsored equally by the U.S. Department of Energy (through a contract with the National Academy of Sciences) and the Japanese Ministry of Health and Welfare.
Currently, there are two sets of dose-estimates in the A-Bomb Study. The set established in 1965 is called T65DR. A partial, interim set of new dose-estimates, introduced in 1986, is called DS86. In making our point about how few of the survivors received high doses, we will state the dose-estimates in both dosimetries. Doses shown on the next page refer to average whole-body internal organ-doses, and they are given in centi-sieverts (rems) instead of centi-grays (rads). This change is just the signal that adjustment for the survivors' small exposure to neutrons has been made, and that the doses are equivalent to doses in centi-grays (rads).Initial T65DR: Mean Organ- DS86: Mean Organ- Persons Dose (cSv or rems) Dose (cSv or rems) 66,028 0.66 0.88 14,943 10.99 14.56 4,225 35.36 40.62 6,035 71.31 and up 74.24 and up -------- 91,231
The five most important conclusions
of this book follow sequentially, below.
o -- Finding (1) :
Method for Handling
the Retroactive Alteration
of Dose-Estimates in the A-Bomb Study :
A clear rule in epidemiological research is that one does not change input to a study after any of the study's output is known. Such rules have been established in research not in order to be bureaucratic, but only to ensure believability for the results. It is virtually self-evident that retroactive revisions of a study's input can create Orwellian opportunities to alter the meaning of the existing results.
Nonetheless, the new DS86 dosimetry for the A-Bomb Study has become the occasion for retroactively altering the entire architecture of this study, and destroying its continuity. The details are thoroughly documented in our Chapters 5 and 10.
There is a "right" way and a "wrong" way to handle new insights about dosimetry in any study.
We emphatically welcome new insights, and Finding Number One of this book is the demonstration of a method for introducing the new DS86 dosimetry into the A-Bomb Study without putting the study's scientific credibility into peril. Our way of handling the new DS86 dosimetry is very different from its current handling elsewhere -- handling which we regard as at variance with acceptable practice in prospective epidemiologic research.
In Chapter 25, we show that the "wrong" approach to the new DS86 dosimetry has already raised a puzzling inconsistency on a key risk-issue, and that the problem can be resolved only by restoring the study's legitimate continuity.
We do not think that the meaningful rules of research can just be disregarded in this field. We consider our Finding Number One as more important than ever, because the 1988 UNSCEAR and 1990 BEIR-5 reports do not question the current handling of the retroactive alterations at all.
o -- Finding (2) :
Cancer-Risk at Moderate
and High Dose-Levels, Acute Delivery Only :
Substantial agreement exists between this book and the new UNSCEAR and BEIR reports with respect to cancer-risk per rad from moderate and high doses acutely delivered, now that those committees have greatly increased their past estimates. This finding indicates that our independent methods and theirs can lead to the same results.
o -- Finding (3) :
Cancer-Risk at Low Doses,
Acutely and Slowly Delivered :
Serious disagreement exists between this book and the radiation committees about the cancer-risk from low-dose exposure, either acutely or slowly received -- and acute-low and slow-low doses are the ones which occur in the overwhelming share of human exposures.
This book, using human evidence exclusively, arrives at risk-estimates for acute-low and slow-low exposures which are up to 30-fold higher than the wide range of values provided by UNSCEAR and BEIR. Chapters 22, 23, and 25 show that there is no mystery about the source of disagreement. The record shows that the radiation committees reach approximately the same conclusions as we do with respect to the relevant human evidence, but then the committees recommend use of what we call more "optimistic" (less disturbing) findings based on other species.
We wish our own risk-estimates were lower -- for no one welcomes potency in a carcinogen -- but we cannot ignore the direct human evidence.
o -- Finding (4) :
Disproof of Any Safe Dose or Dose-Rate :
Influential segments of the radiation community have been speculating (especially since the Chernobyl accident) about a "threshold" -- namely the notion that low doses and dose-rates may be completely safe. Indeed, some segments are speculating in print that there may be a positive net benefit for human health from low-dose exposure -- a speculation known as "hormesis." The 1988 UNSCEAR Report does not challenge either of the two speculations.
By contrast, we do.
In Chapter 35, we examine studies which are invoked in the name of hormesis, and we find that they provide no scientific basis to support such speculation.
In Chapters 18 through 21, we prove beyond reasonable doubt that no safe dose or dose-rate exists with respect to radiogenic cancer. Our disproof of a threshold is based on human evidence. Both the 1988 UNSCEAR and 1990 BEIR reports fail to address our disproof, although an earlier version of the disproof circulated widely in the radiation community.
In 1987, the U.S. Department of Energy or DOE released its report on the estimated health effects from the Chernobyl accident. The report, which we discuss in detail in our Chapter 24, asserts at every occasion that fallout from the accident may cause no extra cancers at all beyond the immediate vicinity -- which is the same as asserting that there may be a safe dose and dose-rate. The authors (one of whom is on the 1988 UNSCEAR Committee) call this the "zero risk model" (Doe87, p.J.8) and elsewhere, they state that, "There are no direct data that confirm that a few random ionizations in tissue cause fatal cancers" (Doe87, p.7.5).
This book provides those data. And, by reasonable scientific standards, these data rule out the threshold idea with regard to the radiation-induction of human cancer.
o -- Finding (5) :
Implications for Human Health :
The practical implications for human health, of realistic versus mistaken risk-estimates in this field, can be illustrated by evaluation of the Chernobyl accident, but this accident is just "the tip of the iceberg."
Proposals are pending to exclude very low-dose exposure of entire populations from consideration in risk-estimates, and also to handle a large share of radioactive waste as if it were not radioactive -- in other words, to declare a threshold by using edict to over-rule evidence.
It is self-evident that if a mistaken notion about safe doses and dose-rates prevails in this field, human exposures to ionizing radiation will rise dramatically -- from occupational, environmental, and medical doses. Quite aside from heritable genetic consequences, which are not discussed in this book, such a mistake would be far from trivial. Over time, it could mean cancer inflicted on a hundred million or more humans.
Indeed, low-dose ionizing radiation may turn out to be the most important single carcinogen to which huge numbers of humans are actually exposed. No one can possibly be sure yet, in the absence of comparable data on all the other human carcinogens and on the magnitude of exposure to them.
In short, Finding Number Five is that the practical implications for human health are extremely high in the so-called "radiation controversy."
Our independent analysis of the human evidence arrives at seriously different conclusions from those put forth by the radiation community. Readers who take our step-by-step journey in this book, from the evidence to the conclusions, will be in a position to judge for themselves whether or not our conclusions are believable.
The five key findings are reviewed in greater detail in our Closing Statement (Chapter 25).