(Key words: radiation, cancer, doses, ionizing radiation, risk)
AMERICAN JOURNAL OF PHYSICS
Effects of Ionizing Radiation at Low Doses
(Received 2 September 2011; accepted 27 October 2011)
University, Cambridge, MA 02138
(Updated on November 14th 2011)
I. Journals are listed in the following order. General journals, Cancer and Environment journals, and Radiation specific journals. Many of the most important results are published in the general journals, but detail is usually found in the radiation‑specific journals:
American Journal of Epidemiology
Journal of the American Medical Association
British Medical Journal
Cancer and Environment
New England Journal of Medicine
Science of the Total Environment
Journal of the National Cancer Institute
Journal of Radioanalytical and Nuclear Chemistry
Radiation Specific journals
Applied Radiation and Isotopes
International Journal of Radiation Biology
Journal of Environmental Radioactivity
Radiation and Risk (from Obninsk, Russia)
Radiation and Environmental Biophysics
II. Books and Major Compilations
Of the six books listed, the first is intended for physicians. Nonetheless, there is a lot of physics therein, and all can be read by physicists with great profit. The second is the classic text and the third a more recent text on radiation protection.
1. Medical Effects of Ionizing Radiation, edited by F.A.Mettler and A. C. Upton, 3nd edition. (W.B. Saunders, Philadelphia, 2008). (I)
2. Principles of Radiation Protection, K.Z. Morgan and J.E. Turner, (Wiley, New York, 1967). (E)
3. Radiation Protection: A Guide for Scientists and Physicians, J. Shapiro, 4th edition (Harvard University Press, Cambridge, MA, 2002). (E)
4. Radiation Carcinogenesis: Epidemiology and Biological Significance, J.D. Boice, Jr. and J.F. Fraumeni, Jr. (Raven Press, New York, NY, 1984). (I)
5. Health Effects of Low‑Level Radiation, S. Kondo. (Kinki University Press, Osaka, Japan, 1993). (E)
6. Health Effects of Exposure to Low‑Level Radiation, edited by W.R. Hendee and F.M. Edwards. (Institute of Physics Publishing, Bristol, UK, 1996). (E)
The reports of the United Nations Scientific Committee on the Effects of Atomic Radiation (abbreviated and pronounced UNSCEAR) are voluminous. They include reports on exposures from many countries and a summary of much of the scientific literature. Although in general the reader should look at the latest report first, they are not completely repetitive and earlier volumes contain some information not present in the later ones. In addition, a study of the changes helps the reader to follow the changes in scientific understanding.
7. Sources and Effects of Ionizing Radiation, Report of the United Nations Scientific Committee on the Effects of Atomic Radiation. United Nations, General Assembly Official Records: 13th Session, Suppl. 17 (A/3838), (UNSCEAR, 1958). (I)
9. Atomic Radiation Sources and Biological Effects of Ionizing Radiation, United Nations Scientific Committee on the Effects of Ionizing Radiation, Report to the General Assembly, United Nations, New York. (UNSCEAR, 1982). (I)
10. Genetic and Somatic Effects of Ionizing Radiation, United Nations Scientific Committee on the Effects of Atomic Radiation, Report to the General Assembly, with Annexes. United Nations, New York. (UNSCEAR, 1986). (I)
11. Sources, Effects, and Risks of Ionizing Radiation, United Nations Scientific Committee on the Effects of Ionizing Radiation, Report to the General Assembly, United Nations, New York. (UNSCEAR, 1988). (I)
12. Sources and Effects of Ionizing Radiation, United Nations Scientific Committee on the Effects of Atomic Radiation, Report to the General Assembly, including annexes, United Nations, New York. (UNSCEAR, 1993). (I)
13. Sources and Effects of Ionizing Radiation, United Nations Scientific Committee on the Effects of Atomic Radiation, Report to the General Assembly, with scientific annexes, United Nations Sales Publication E.94.1X.11, United Nations, New York. (UNSCEAR, 1994). (I)
14. Sources and Effects of Ionizing Radiation, United Nations Scientific Committee on the Effects of Atomic Radiation, Report to the General Assembly, with scientific annexes, United Nations Sales Publication E.08.IX.6, United Nations, New York. (UNSCEAR, 2006). (I)
15. Sources and Effects of Ionizing Radiation, United Nations Scientific Committee on the Effects of Atomic Radiation, Report to the General Assembly, with scientific annexes, United Nations Sales Publication E.10.XI.3, United Nations, New York. (UNSCEAR, 2008). (I)
The US National Academy of Sciences has a Committee on the Biological Effects of Ionizing Radiation (abbreviated and pronounced BEIR) that regularly surveys the literature on the effects of ionizing radiation. In contrast to the UNSCEAR reports, which are mainly a compilation of data, BEIR reports are judgmental.
16. The effects on populations of exposure to low levels of ionizing radiation, Report of the Advisory Committee on the Biological Effects of Ionizing Radiations (BEIR 1972) (National Academy Press, Washington, D.C., 1972). (I)
17. The effects on populations of exposure to low levels of ionizing radiation (BEIR III 1980) (National Academy Press, Washington, D.C., 1980). (I)
18. Health Risks of Radon and Other Internally Deposited Alpha Emitters (BEIR IV) (National Academy Press, Washington, D.C., 1988). (I)
19. Health Effects of Exposure to Low Levels of Ionizing Radiation (BEIR V, 1990) (National Academy Press, Washington, D.C., 1990). (I)
20. Health Effects of Exposure to Low Levels of Ionizing Radiation Health Effects of Exposure to Indoor Radon (BEIR VI, 1999) ( National Academy Press, Washington, D.C., 1999). (I)
21. Health Risks from Exposure to Low Levels of Ionizing Radiation (BEIR VII Phase2, 2006) (National Academy Press, Washington, D.C., 2006). (I)
The National Council of Radiological Protection and Measurements (NCRPM) has produced over 100 reports. Most are too detailed to be of general interest, but I list the following particularly useful ones here.
22. Influence of Dose and Its Distribution in Time on Dose‑Relationships for Low‑LET Radiation, National Council on Radiation Protection and Measurements, Report No. 64 (NCRPM, Bethesda, MD, 1980). (I)
23. Evaluation of Occupational and Environmental Exposures to Radon and Radon Daughters in the United States, National Council on Radiation Protection and Measurements, Report No. 78, (NCRPM, Bethesda, MD, 1984). (I)
30. Sources and Magnitude of Occupational and Public Exposures from Nuclear Medicine Procedures, National Council on Radiation Protection and Measurements, Report No. 124 (NCRPM, Bethesda, MD, 1996). (E)
International Commission on Radiological Protection (ICRP). Although no specific reports are referred to here, this commission, started in 1928, issues many reports.
III. Conference Proceedings
The International Atomic Energy Agency, a UN agency set up to promote peaceful uses of nuclear energy, and more recently to monitor (and aid in controlling) military uses, regularly holds conferences and issues a number of reports. The conference on low doses of radiation is particularly important since it contains reports from a number of people with divergent views.
34. International Conference: Low Doses of Ionizing Radiation: Biological Effects and Regulatory Control, International Atomic Energy Agency, Seville, Spain, IAEA‑TECDOC‑976, IAEA‑CN‑67/63, 223‑226 (1997). (I)
36. Catalogue of studies on human health effects of the Chernobyl accident, 1995 update. In: WHO European Center for Environment and Health. Rome, Italy: World Health Organization (1995).(I)
One crucial feature of the data is that radiation does not seem to cause any medical or biological effect that cannot also occur naturally. It merely increases the probability of the effect. This fact is very important both for understanding possible dose‑response curves and for deciding what if anything to do about radiation at low doses. It also leads us to ask a general question. Does radiation add an additional probability of developing cancer (an absolute-risk model) or does it multiply the probability that is there from natural or other causes (a relative-risk model). Although both are discussed in all the BEIR reports, it is noteworthy that the emphasis has changed from the absolute risk model in BEIR I (1970) to the relative risk model in BEIR III, BEIR V and BEIR VII.
International Atomic Energy Agency.
Radiation Protection Division of the Health Protection Agency (HPARPI) is the successor to the National Radiological Protection Board (NPRB) in the UK.
These sites all have information on important reports and papers on radiation from RERF, IAEA, NRPB/HPARPD, ICRP and NCRPM respectively. Some of the more recent can be downloaded.
The American NuclearSociety maintains this interactive webpage so that anyone may estimate his or her integrated dose. The author's dose in the previous 12 months was 2.4 Rems (0.024 Sv) mainly due to medical exposures.
V. What is the effect at moderate to high doses?
44. "Hazards of Ionising
Radiation: 100 Years of Observations on Man," R. Doll, Br. J.
Cancer 72, 1339‑1349
This very important review paper by the leading epidemiologist Sir Richard Doll discusses the effects that one might expect from general biological principles and the general status of the field. It is a good start to studying the subject. He asks several questions:
(1) Does radiation exposure lead to cancer?
(2) Does radiation exposure lead to heart disease?
(3) Does radiation exposure lead to other diseases?
(5) Does radiation exposure lead to birth defects?
Most of the studies address only (1) cancer, and the data do indeed suggest that cancer induction is the dominant adverse effect of radiation. The data are better than for the other outcomes largely because the observed effects are greater. Several groups of radiation‑induced cancer can be distinguished with different characteristics.
Leukemia was the first cancer to be noticed in the atomic-bomb survivors. Leukemias began to appear 5 years after the exposure and continued to appear for another 20 years, after which the number of leukemias (almost) ceased. Radiation induces leukemias more readily than other cancers. Therefore leukemias are often considered to be a "marker" for radiation effects. But the variation with age is clearly in great contrast to that of the "solid" cancers, and at old age even an "absolute-risk" model would overpredict the number of leukemias.
A small increase of leukemia has been seen in children of workers near nuclear sites such as Sellafield (U.K.) and Douneray (U.K.). Although statistical significant it is hard to reconcile the numbers with the measured doses. Reference 46 reviews the data. Kinlen found a bigger effect at Glenrothes new town north of Edinburgh (with no nuclear facilities), and postulates that the observed effect is a viral effect of a new population.
B. Solid Cancers (other than lung)
Also in reference 45 are data on cancers in tissues of the body (other than those connected with blood), hereinafter called solid cancers. These do not appear until 20 years after the exposure and have continued to appear for 50 years. The increase of cancer with radiation dose seems to follow a "Relative-Risk" pattern whereby the risk, after the latent period of 20 years, is increased by a constant fraction relative to the background at that age.
For the considered dose interval (1-300 mSv) and for the period 1991-2001, the spontaineous incidence rate of solid cancer among emergency workers agrees, within confidence intervals, with that for the general Russian population. The presented estimates of radiation risk should be treated as preliminary because the follow-up period is rather short and the number of cases considered in the analysis is relatively small.
C. Lung Cancers
Lung cancers have a special place
because the lung is also the point of entry for a major
exposure route. One of the surprises of the atomic age (i.e.
since 1945) was that an excess of lung cancers appeared among
uranium miners. In some of the early studies, they seemed to
appear only among Caucasian miners and not among native Americans (Indians). There was
some speculation of a racial difference in sensitivity. This
speculation was rejected and the data somewhat resolved by
further follow up, but also by the observation that there are
fewer tobacco smokers among the Indian miners. Most analysts
have assumed that the lung cancers are due to radon rather
than to any other pollution in the mines (dust, etc.) although
there is still room to question this. The main concern is that
inhaled particles or radionuclides
might cause lung cancer. For example radon gas in uranium
mines produces lung cancers by alpha particle irradiation to
the lung. This is reviewed in references 18 (BEIR IV,1988) and 23 (NCRPM,1984).
The work in this paper summarizes the evidence for the idea that radiation is synergistic with tobacco smoking, in that the effects multiply and do not merely add. This makes some intuitive sense since both smoke and radiation are highly irritant to the lung tissue. This idea can therefore be used to guide the questions which are asked of the data at low doses.
D. Childhood Cancers
52. "Cancer Mortality Among Atomic Bomb Survivors Exposed in utero or as Young Children (1950‑1992)," R.R. DeLongchamps, K. Mabuchi, Y. Yamamoto, D.L. Preston, Radiation Research 147, 385‑395 (1997). (E)
54. "Childhood Leukemia in Belarus Before and After the
Chernobyl Accident," E.P. Ivanov, G.V.
Tolochko, L.P. Shuvaeva, S. Becker, E. Nekolla and A.M.
Kellerer, Radiat. Environ. Biophys. 35(2), 75-80 (1996). (E)
The Chernobyl accident is now 25 years old and childhood cancers (leukemias, ref. 54, and thyroid, ref. 56 and 57 ) should have been seen within a few years. The lack of leukemias in the general population is consistent with a linear extrapolation from higher doses. But although the idea that X rays increase leukemia is generally accepted, it is still possible that causality works in the other direction, and that the reason for the X rays was a medical problem associated in some way with a latent leukemia. For that reason it is especially interesting to look at the pregnant women who were exposed at Hiroshima or at a radiation accident such as at Chernobyl. A small effect is seen. It is not larger than and could be smaller than the effect suggested by Stewart and Kneale (ref. 51).
56. "Chernobyl‑Related Thyroid Cancer in Children of Belarus: A Case‑Control Study," L.N. Astakhova, L.R. Anspaugh, G.W. Beebe, A. Bouville, V.V. Drozdovitch, V. Garber, Y.I. Gavrilin, V.T. Khrouch, A.V. Kuvshinnikov, Y.N. Kuzmenkov, V.P. Minenko, K.V. Moschik, A.S. Nalivko, J. Robbins, E.V. Shemiakina, S. Shinkarev, S.I. Tochitskaya, M.A. Waclawiw, Rad. Research 150, 349‑356 (1998). (I)
The childhood thyroid cancers from Chernobyl, while mostly non‑fatal are numerous. They were a surprise although in retrospect they should not have been.
of Thyroid Cancer After Exposure to 131I in Childhood," Cardis et al., Journal of the National
Cancer Institute 97(10),
E. Medical Exposures
60. "Mortality from Breast Cancer After Irradiation During Fluoroscopic Examination in Patients Being Treated for Tuberculosis," A.B. Miller, G.R. Howe, G.J. Sherman, J.P. Lindsay, M.J. Yaffe, P.J. Dinner, H.A. Risch, and D.L. Preston, N. Engl. J. Med. 321, 1285‑1289 (1989). (I)
F. The Other Outcomes
Shimuzu et al. (ref. 63) found an increase in several other medical outcomes as a result of the lower levels of exposure. In particular, heart disease appears with a frequency about one third of the frequency of cancer. Boice (ref. 62) and references therein discuss how radiation for cancer treatment can cause cardiac problems.
64. "Cardiac Exposure in Breast Cancer Radiotherapy: 1950s-1990s," Taylor, C.W., F.R.C.R., Nisbet, A., McGale, P., Darby, S.C., International Journal of Radiation Oncology, Biology and Physics 69(5), 1484-1495 (2007).(I)
65. "Cardiac Dose from Tangential Breast Cancer Radiotherapy in the Year 2006," Taylor, C.W., F.R.C.R., Povall, J.M., Nisbet, A., McGale, P., Dodwell, D., Smith, J.T., Darby, S.C., International Journal of Radiation Oncology, Biology and Physics 72(2), 501-507 (2008).(I)
of Parents Exposed to Atomic Bombs: Estimates of the Genetic
Doubling Doses of Radiation for Humans," J.V.Neel, W.J. Schull,
A.A. Awa, C. Satoh, H. Kato, M. Otake,
and Y. Yoshimoto, Amer. J. Human. Genet.
67. "The Growth and Development of Children Exposed in utero to the Atomic Bombs in Hiroshima and Nagasaki," J.W. Wood, R.J. Hoehn, S. Kawamoto and K.G. Johnson". Amer. J. Public Health 57, 1374‑1380 (1967). (A)
68. "Threshold for Radiation‑Related Severe Mental Retardation in Prenatally Exposed A‑bomb Survivors: a Reanalysis," M. Otake, M.J. Schull, and Lees Brit. J. Radiation Biology 70(6), 755‑763 (1996). (A)
V. The Effects of Dose Rate
From general principles one might guess that a high radiation dose given at a low rate over a period of years might have a different (probably smaller) effect from the same dose given in a short time, although the very use of a total DOSE summed over a long time period, of the order of a lifetime implies that the difference is unlikely to be large. Data from animal exposures to shows that there is a reduction in cancers (for the same total dose) at low dose rates. A Dose Rate Reduction Factor (DRRF) is usually introduced to describe this. The following papers can be used to address this directly.
70. "Issues in the Comparison of Risk Estimates for the Population in the Techa River Region and Atomic Bomb Survivors," M.M. Kossenko, M.O. Degteva, O.V. Vyushkova, D.L. Preston, K. Mabuchi, and V.P. Kozheurov, Radiation Research 148, 54‑63 (1997). (I)
71. "Studies on the Extended Techa River Cohort: Cancer Risk Estimation", M.M. Kossenko; D.L. Preston; L.Y. Krestinina; M.O. Degteva; N.V. Startsev; T. Thomas; V.P. Vyushkova; L.R. Anspaugh; B.A. Napier; V.P. Kozheurov; et al., Radiation and Environmental Biophysics 41(1), 45‑8 (2002). (I)
Radiation Exposure and Cancer Mortality in the Techa River Cohort", Krestinina, L.Y., Preston, D.L., Ostroumova, E.V., Degteva, M.O., Ron, E., Vyushkova, O.V., Startsev, N. V., Kossenko, M.M. and Akleyev, A.V., Radiation Research 164(5), 602-611 (2005).
In 1955‑56 radionuclides spilled from the reservoir in Lake Karachay into the Techa River. Villagers drank the water and ingested many radionuclides. For 40 years the health of 30,000 villagers around the Techa River has been studied. The exposures were mostly internal exposure from the bone seeker strontium 90. The doses can be moderately well determined by subsequent examination of radioactivity of teeth and other bones. This then enables a bone marrow dose to be determined, which is the appropriate organ dose for describing leukemia incidence. In contrast, the "solid" cancers depend upon external doses which are far less well determined. There are fewer leukemias than a linear plot from the Hiroshima-Nagasaki data. This could be a DRRF of 3 with a large error band from 2 to 6 or a quadratic relationship of effect with dose. The dose rate reduction factor for solid cancers is about 1 with a much larger error band.
For many years it had been rumored that the workers at the MAYAK atomic bomb plant in the Urals received large radiation doses. Attempts from the western countries to discover what they were fruitless until 1991 when a description was published in Russian in the journal Priroda. In this paper, these data are discussed and show that the cancer rate was less than suggested by the Japanese atomic bomb data by a Dose Rate Reduction Factor of about 3.
73. "Verification of Occupational Doses at the First Nuclear Plant in the Former Soviet Union," A. A. Romanyuka, D. Regulla, E. K. Vasilenko, A. Wierser, E.G. Drozhko, A. F. Lyzlov, N. A. Koshurnikova, N. S. Shilnikova, and A. P. Panfilov Appl. Radiat. Isot. 47, 11‑12, 1277‑1280 (1996). (A)
74. "Mortality Among Workers with Chronic Radiation Sickness," N. S. Shilnikova, N. A. Koshurnikova, M. G. Bolotnikova, N. R. Kabirova, V. V. Kreslov, A F. Lyzlov, and P. O. Okatenko., Health Physics 71(1), 86‑89 (1996). (A)
The doses to the MAYAK workers are in principle well determined by personal monitors. Personal monitors even at that early date were reliable in the USA. In principle it should be possible to determine a dose rate reduction factor both for leukemia and for the principal solid cancers.
76. "Cancer Mortality Risk among Workers at the Mayak Nuclear Complex", N.S. Shilnikova, D.L. Preston, E. Ron, E.S. Gilbert, E.K. Vassilenko, S.A. Romanov, I.S. Kuznetsova, M.E. Sokolnikov, P.V. Okatenko, V.V. Kreslov and N.A. Koshurnikova, Radiation Research 159, 787-798 (2003). (A)
An interesting subsidiary set of data comes from the MAYAK workers. This is because the workers were exposed to plutonium by inhalation and might be expected to develop lung cancer in the same way that uranium miners develop lung cancer from uranium. These are the only workers exposed to plutonium (239 mostly) at doses high enough to have an appreciable incidence of lung cancer. While the first studies suggested that the dose‑response relationship is quadratic with dose (in qualitative agreement with animal data) and therefore a low dose effect approaching zero seemed to make sense, a more careful look at the data suggests that a linear dose response relationship fits the data better. However the doses are not low and a threshold or reduced effect at low doses is possible.
77. "Estimated Long Term Health Effects of the Chernobyl Accident," E. Cardis, G. Anspaugh, V.K. Ivanov, et al., presented to the IAEA Conference: One Decade after Chernobyl: Summing up the Consequences of the Accident, International Atomic Energy Agency, Vienna (1996). (E)
VI. Low and Very Low Doses
A. The One-Hit Theory
The physicist Geoffrey Crowther produced the first theory of radiation‑induced cancer of which this author is aware. The idea is that when a cell was ionized by radiation it would initiate a cancer. The probability of ionizing a cell in a given time is clearly proportional to the radiation intensity and hence one gets a theory that cancer induction is linear with dose even at low doses. But this theory in its simplest form cannot be true. Cosmic rays and background radiation ionize millions of cells every day and yet lifetime cancer incidence is only about 30% in the US population. Other effects must modify this idea drastically. Cells can be repaired; they can be excreted without leading to a cancer, and so on. Whether cancer incidence is linear with dose depends therefore on whether these important mechanisms are constant with dose or otherwise. The concept that even small amounts of radiation can induce cancer is deeply embedded in the public consciousness and influences public policy and legal actions. It is often called the One-Hit Theory. This cannot be tested directly and remains an unprovable hypothesis. But it is vitally important to realize that the inverse is demonstrably false. Every cell ionization does not lead to a cancer. It becomes necessary to discuss what is the lowest level that is known to cause increases in cancer.
B. What is low dose?
The concept of what constitutes a low dose changed after 1945. A typical chest X ray gave a dose of 1 Rem (0.01 Sv) and at least one jurisdiction (UK) went as far as to propose mandating such an X ray every year. (The bill died in the House of Lords because of the objections of the physicist Lord Cherwell.) In contrast, in 1987 a proposal of the U.S. Nuclear Regulatory Commission to call a radiation exposure that gave no more than 1 milliRem (0.00001 Sv) to any person "Below Regulatory Concern" was withdrawn after some vocal public opposition. Yet natural background exposures are a few hundred milliRems or 100 times this amount. Thus "low dose" now means doses as low as, and usually well below background.
C . Variation of Cancer Incidence with Background Exposure
One way of attempting to understand the effect of radiation on people at low doses is to understand the variation of cancer mortality with natural radiation exposure. In many studies cancer mortality seems to be lower in areas with high radiation dose.
The radiation levels in the Rocky Mountain states are higher than in the Gulf states, yet the cancer rate is lower. This effect may be seen throughout the U.S. and Canada (see ref. 26), but confounding factors may exist. Many Mormons live in Utah and mountain states who do not smoke or drink alcohol or coffee and seem to have half the cancer rate of their non‑Mormon neighbors. In New Jersey also there is much (presumably polluting) industry. Thus many analysts conclude that the only fact of importance from these studies of geographical variation is that radiation at these levels (a few hundred milliRems per year of 10‑20 Rems per lifetime) is not an important factor in developing human cancers compared to other factors.
High background radiation in China does not seem to lead to high cancer rates. It is unclear how much this is due to life style factors or other pollutant effects.
80. "High Background Radiation Research in China", L. Wei, et al., Atomic Energy Press, Beijing, China (1996). (I)
D. The Relationship of Low Dose Effects and Background - Cancer Modeling.
When doses were called low even when they were more than background dose, it was possible to discuss logically the effects of radiation independently of whatever causes the background. Now that low means radiation doses 100 times smaller than background, it is necessary to consider them together. However, very few scientists and scientific papers do this logically. It is necessary to use theoretical models to suggest what the effects can be. The discussion below is primarily about cancer induction.
In the first of these papers, Guess, Crump and Peto point out that whatever the basic biological process relating a dose to cancer, a differential linearity results provided that the radiation dose and the background act on the biological system in the same way. Indeed this is implied in Doll and Armitage's well-known multistage theory of cancer. Since pathologists cannot distinguish the cancers produced by radiation and those produced by background, this is an assumption that has not been refuted. Crawford and Wilson went further and pointed out that the argument is a general one and can apply to other outcomes than cancer, and other causes than radiation such as respiratory problems caused by air pollution or cigarette smoking.
There is a possibility that the cancers from radiation and background can be distinguished, by DNA analysis for example. In which case the above argument might not apply. Rowley and Le Beau (ref. 84) have shown that the chromosome structure of an Acute Myelogenous Leukemia (AML) occurring subsequent to and presumably caused by radiotherapy was appreciably different from those that occur naturally. If this turns out to be a general result, the low dose extrapolation arguments of references 81, 82 and 83 must be drastically reconsidered.
E. Epidemiological studies of Low Dose Behavior
The following paper addresses the few epidemiological studies with a large enough data sample, and with systematic errors well enough controlled, that can be used to discuss directly the shape of the dose response curve below a total dose of 50 Rems (0.5 Sv). The paper focuses on the data on atomic-bomb survivors.
There have been
various studies of the cancer rates among workers in nuclear
power plants and other nuclear facilities. The most detailed
study in the United States was in reference 87. But a more
recent collaborative study in 15 countries (ref. 88) shows a
small effect. This is not merely a "meta‑analysis" of several
papers but a combined study of those groups where the data are
deemed reliable. The additional number of leukemias seen is
consistent with an extrapolation from the number at higher doses
(but the lower 95th percentile of the number is close to zero).
The number of additional "solid " cancers is close to zero but
the upper 95th percentile is close to the linear extrapolation
from higher doses. Taken together these data suggest that much
larger numbers suggested in references 88 and 89 can be
87. "Cancer in Populations Living Near Nuclear Facilities: A Survey of Mortality Nationwide and Incidence in Two States," S. Jablon, Z. Hrubec, J. D. Boice, Jr., J. Amer. Med. Assoc. 265(11), 1403‑1408 (1991). (E)
15-Country Collaborative Study of Cancer Risk among
Radiation Workers in the Nuclear Industry: Estimates of
Radiation-Related Cancer Risks", Cardis
et al., Radiation Research Society 167, 396-416 (2007). (E)
A distinguished epidemiologist challenges Cohen's studies and implicitly all other "ecological" studies.
95. "Residential Radon Exposure and Lung Cancer among Nonsmoking Women," M.C.R. Alavanja, R.C. Brownson, J.H. Lubin, J. Chang, C. Berger and J.D. Boice, Jr., J. Natl. Cancer Inst. 86, 1829‑1837 (1994). (A)
The following paper summarizes of the evidence that suggests that the mining cancer data underestimate the risk of uranium miners. Such an underestimate would be even harder to reconcile with the data of Cohen.
97. "Radon‑exposed Underground Miners and Inverse Dose‑rate (protraction enhancement) Effects," J.H. Lubin, J.D. Boice, Jr., C. Edling, R.W. Hornung, G. Howe, E. Kunz, R.A. Kusiak, H.I. Morrison, E.P. Radford, J.M. Samet, et al., Health Physics 69(4), 494‑500 (1995). (A)
F. Larger Effects
The following is the foremost and most logical of a set of claims that the effect of a low dose is greater than the "establishment" wisdom. At the time the "establishment" used an absolute risk model which gives a smaller effect than the relative risk model now accepted for solid cancers. But Gofman's estimate was still 5 times the relative risk model. Although primarily concerned with radiation exposures from peaceful nuclear energy, Gofman is consistent in also pointing out high medical exposures although he is clearly less eager to oppose them.
98. Radiation and Human Health, J.D. Gofman (Sierra Club Books, San Francisco, 1981). (I)
99. ECRR 2010 Recommendations of the European Committee on Radiation Risk The Health Effects of Exposure to Low Doses of Ionizing Radiation, C. Busby, R. Bertell, I. Schmitz‑Feuerhake, M. S. Cato, A. Yablokov (Regulators Edition, Green Audit, August 2010). (E)
This multinational group is the latest in the idea that the effect of the dose is undetermined.
The following paper discusses several claims that at radiation doses at or below the background cancers are produced. These reports often select data or otherwise fall into statistical "traps" or errors. Rarely (Gofman is an exception) is there a discussion of the effect of the background and why many more people are not dying naturally from cancer in high radiation areas, which would be expected if their claims were true.
G. Is radiation good for you?
101. "Health Effects of Low‑dose Radiation: Molecular, Cellular, and Biosystem Response," M. Pollycove, and C.J. Paperiello, in: Low Doses of Ionizing Radiation: Biological Effects and Regulatory Control, International Atomic Energy Agency, Vienna, IAEA‑TECDOC‑976, IAEA‑CN‑67/63, 223‑226 (1997). (A)
It is important to realize that there are many other possibilities. It is possible, for example, that radiation cures a commonly occurring cancer while increasing the less common ones. Although there are no good data on radiation effects this possibility has been suggested for the chemically induced effects. Also it is possible that radiation cures an infectious disease (such as by killing the bacteria) while increasing cancer. A clear example of a substance that is beneficial at low doses and very deleterious at higher ones is ethyl alcohol.
Alcohol is a substance which has been
studied for a much longer period (millenia)
than radiation. In this
paper Sir Richard Doll points out that at low doses it reduces
the risk of stroke, while it is carcinogenic also (especially
in conjunction with tobacco smoking) and at even higher doses
the narcotic effects can cause many adverse effects such as
car accidents. The implication here is that the same mixture
of outcomes can occur with radiation.
H. Policy Implications: Man Rems (Person‑Sievert) or Rems/man (Sv/Person)?
The first imperative is to understand what question you are asking. The relevant policy may be different for different questions.
In 1978 Dr. Dunster, while head of the Health and Safety Executive of the U.K., stated: " all politicians would prefer a dead body to a frightened voter." A dead body does not vote: a person who fears he may have cancer does. This dramatically brings out a potential bias in these discussions.
In this category are recommendations by the International Atomic Energy Agency (IAEA).
One criterion is for external acute exposure of 2.5 Gray at a depth of 0.5 cm in tissue. This criterion is more applicable to a localized radioactive source accident than for the effective whole body dose applicable to a nuclearor reactor or RDD device and must be used with caution.
There are few discussions, and none in the regulatory arena yet, of how such important individual decisions or decisions of small groups work in practice. Obviously a sensible decision involves careful balancing of alternative non-radiation hazards work out. Three examples are :
It is surprising that even 66 years after the detonations at Hiroshima and Nagasaki, mankind still has not come to grips with what might happen in another nuclear explosion. The above papers argue that an explosion at ground level, rather than the 500 feet altitude at Hiroshima and Nagasaki will increase the number of radiation casualties. They also argue that merely running directly away from the site may be the wrong thing to do. Sheltering in place can cut our exposure for the first day, and when the direction of the wind blown plume is know, walking sideways from the plume is the best response.
The following report discusses the evacuation decision at Fukushima and argues that it was deleterious to public health. It points out that as soon as there is an important adverse effect of any action then a risk-benefit comparison must take this into account. The IAEA and other guidance in the above references omit this in their documents and may therefore be deleterious to overall public health.
111. "Lessons from History of Radiation use and Nuclear Accidents particularly Fukushima", R. Wilson, The 44th Seminar on Planetary Emergencies World Federation of Scientists, Erice Sicily (August 20th, 2011). To be available in a full volume of the papers of the seminar at World Scientific. (E)
114. "Implementation of the Principle of As Low As Reasonably Achievable (ALARA) for Medical and Dental Personnel, National Council on Radiation Protection and Measurements, Report No. 107 (NCRPM, Bethesda MD, 1990). (E)
This reference also recommend a de minimis level for an individual dose of 1 milliRem (100 m Sv). Another suggestion was to note that the difference in radiation exposure of about 50 mRem/year (0.5 MSv/year) between sea level and in the Rocky Mountains due to cosmic rays and increased terrestrial radioactivity is generally accepted without question. Although the first was proposed by the NRC there were public political objections and the proposal was not finalized. Many scientists believe that their time and that of the public is better spent in insisting that these guidelines be followed (and not exceeded) with a coherent risk/cost/benefit analysis rather than addressing the possibility of a threshold at low doses that may be impossible to prove rigorously.