Health Risks of Ionizing Radiation: - Clark University

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10 PRECONCEPTION EXPOSURES Several epidemiological studies have examined the possible association between occupational exposure of parents to radiation and the development of cancer in their children. The theoretical mechanism for this kind of effect originally involved reproductive cells- if a sperm or egg is irradiated then the genetic material in the cell could be altered. These mutations would occur before conception but they would be passed on to the child and could increase the child’s risk of developing cancer. More complex mechanisms are now considered plausible, as discussed below and in appendix C. The majority of studies focus on exposure of fathers, largely because men are more frequently exposed to radiation in the workplace, and this type of exposure is typically referred to as paternal preconception irradiation, or PPI. The first disease to be highlighted as a possible effect of PPI was leukemia and it has subsequently received a great deal of attention. In these studies leukemia is commonly grouped with non-Hodgkin’s lymphoma, and these diseases are collectively referred to as LNHL (leukemia and non-Hodgkin’s lymphoma). The exposure of children in the womb is not addressed in this section because the effect would not be inherited, it would be caused by direct exposure to the child in an early stage of development. This topic is covered largely in the medical irradiation section (section 3). 10.1 The Seascale leukemia cluster and the Gardner hypothesis The case-control study by Martin Gardner et al. (1990) was the first to bring attention to a link between fathers’ occupational radiation exposure 117 and cancer in children. The study followed a journalist’s suggestion in 1983 that childhood leukemias in Seascale, England might be linked to the Sellafield nuclear installation. A government survey determined that the Millom rural district, including the village of Seascale, had 6 childhood leukemia deaths in 1968-78 when only 1.4 would be expected based on national rates. A follow-up case-control study (Gardner et al. 1990) revealed increased risks of leukemia and non-Hodgkin’s lymphoma (LNHL) in children born near Sellafield of fathers employed at the plant (RR 2.44, 1.04- 5.71). The risk was particularly high for children of fathers with total preconception doses (external) of greater than 100 mSv (RR 6.42, 1.57-26.3). In addition, the leukemias were occurring at younger ages than expected, indicating that the damage was occurring very early in the development of the child (Gardner and Snee 1990). The proposed explanation, an external radiation-induced heritable mutation in fathers that increased leukemia risk, became known as the “Gardner hypothesis”. The Gardner hypothesis was challenged on several grounds: • Children of nuclear workers in other places were generally not showing the same relationship as the Sellafield workers’ families living in Seascale (for example see Little et al. 1995). More information has since been collected and many studies do in fact demonstrate similar associations. This is discussed below. • No leukemia was observed in children of the atomic bomb survivors (discussed by Watson (1991) and others).
118 Preconception Exposures • The biological mechanism seemed unlikely. Doll et al. (1994) make this point with several arguments including the fact that radiation damages the genome randomly, so if preconception radiation is affecting sperm cells, other heritable diseases should show an increase along with leukemia. Evidence for these effects is discussed below. • There were other possible explanations for the excess in Seascale. Specifically, the external dose measurements used by Gardner may have been correlated with the dose received from radionuclides in the body (such as uranium, plutonium and tritium). In this case the internal dose or the combined external and internal dose may have been the true cause. Another proposed explanation for the Seascale cluster was that a high degree of population mixing in the communities that the workers lived in might have increased the general exposure to a virus; this virus may have played a role in the development of leukemia. 10.2 Further studies of the Gardner hypothesis in the UK Both of the alternative explanations for the Seascale cluster were explored in a follow-up cohort study of all 274,170 live births in the county of Cumbria 1950-1991 (Dickinson and Parker 2002a). The new cohort study included three more cases of leukemia in the children of workers and generally confirmed the Gardner result (RR 1.9, 1.0-2.2). Although dose estimates for internal radionuclides were apparently not available, researchers typically identify those workers who experienced significant internal exposures by looking at who was monitored, assuming that a worker would only be subjected to monitoring if they were potentially exposed. In the cohort study Dickinson and Parker found a 3-fold increase in LNHL risk in the children of monitored workers (controlling for external exposures), but the result was based on 3 leukemia cases and not significant (RR 2.9, 0.6-9.8). It is important to note that monitored workers were shown to have higher external doses than unmonitored workers (75 mSv median dose vs 27 mSv); this seems to suggest that internal and external dose could be correlated. If true, this would support the idea that the leukemia cluster might be at least partly attributable to internal exposures. Addressing another alternative explanation for the cluster, population mixing and viruses, Dickinson and Parker (2002a) found that population mixing could statistically account for a large part of the leukemia excess in the children of Sellafield workers: The observed excess during 1950-1991 gave a RR of 1.9 (1.0-3.1); this was reduced in the 1969-1991 time window to a RR of 1.1 (0.3-2.8) adjusted for population mixing 1 . On the other hand they showed a significant preconception radiation dose-response relationship within the Sellafield cohort that was not strongly affected by population mixing 2 . Several other studies have looked at LNHL and paternal preconception irradiation beyond Sellafield. One case-control study was based in Scotland (Kinlen et al. 1993) and found no significant associations between PPI and LNHL although all odds ratios calculated by the authors were positive. The case-control study reported by Roman et al. (1993) was important because it found a positive association with relatively low doses. The subjects in this study lived near the Aldermaston and Burghfield nuclear weapon plants in England. Although the fathers who worked at the plant had received less than 5 mSv of external preconception dose there was a significant LNHL risk associated with exposure to radiation on the job (RR 9.0, 1.0-107.8). In a later cohort study of UK nuclear workers Roman et al. (1999) again found an elevated LNHL rate in children of men who were monitored for radiation (rate ratio 3.0, 0.7-13.0). For those cases in which dose information was available there were elevated rates of LNHL that became significant for the highest dose groups 3 . There was also evidence 1 Among children of radiation workers born 1969-1991 and aged 0-6 years 63% of the cases were estimated to be attributable to population mixing and 18% were estimated to be attributable to PPI. (Dickinson and Parker 2002b). 2 The rate ratio per 100 mSv was 1.6 (1.0-2.2) before adjusting for population mixing and 1.4 (0.2-3.1) after adjustment. 3 Leukemia rate ratios were 3.9 (1.0-15.7) for cumulative external doses of ≥100 mSv and 5.4 (1.4-20.5) for doses of ≥10 mSv in the 6 months before conception.
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Health Risks of Ionizing Radiation:
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Contents List of Tables ...........
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Contents iii Rocky Flats ..........
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Contents v APPENDIX A .............
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List of Figures Figure 1-1 Average
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We are indeed grateful to those who
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2 Introduction 1.2 A brief history
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4 Introduction Figure 1-2. The evol
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6 Introduction Figure 1-5(a). Alpha
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8 Introduction In epidemiological s
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10 Introduction precision to detect
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12 Introduction available informati
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14 Background Radiation Figure 2-1.
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16 Background Radiation Figure 2-3.
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18 Background Radiation
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20 Medical Exposures Fi
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22 Medical Exposures
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24 Medical Exposures with national
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26 Medical Exposures localized expo
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28 Medical Exposures (2.1-28.7). Th
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30 Medical Exposures posed 2.69 tim
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32 Medical Exposures with diagnosti
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34 Medical Exposures Table 3-1. Stu
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44 Atomic Bomb Survivors Figure 4-2
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46 Atomic Bomb Survivors
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48 Atomic Bomb Survivors approximat
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50 Atomic Bomb Survivors (ALL), acu
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52 Atomic Bomb Survivors of the 8 t
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5 Nuclear Weapons Testing Over 500
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60 Nuclear Weapons Testing by disti
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62 Nuclear Weapons Testing Figure 5
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64 Nuclear Weapons Testing near the
Page 77 and 78: 66 Nuclear Weapons Testing
Page 79 and 80: 68 Nuclear Weapons Testing
Page 81 and 82: 6 RADIATION WORKERS Introduction Th
Page 83 and 84: 72 Radiation Workers • 50 rem (0.
Page 85 and 86: 74 Radiation Workers work, reports
Page 87 and 88: 76 Radiation Workers Figure 6-5. A
Page 89 and 90: 78 Radiation Workers Figure 6-8. To
Page 93 and 94: 82 Radiation Workers Feed Material
Page 95 and 96: 84 Radiation Workers by Beral et al
Page 99 and 100: 88 Radiation Workers Table 6-1. Leu
Page 101 and 102: 90 Radiation Workers No
Page 103 and 104: 92 Radiation Workers N
Page 105 and 106: 94 Radiation Workers S
Page 107 and 108: 96 Radiation Workers ERR estim
Page 109 and 110: 98 Mayak Workers Table 1. Dose (Gy)
Page 111 and 112: 100 Mayak Workers workers at the ra
Page 113 and 114: 102 Mayak Workers
Page 115 and 116: 104 Uranium Miners enrichment facil
Page 117 and 118: 106 Uranium Miners Samet et al. (19
Page 119: 108 Uranium Miners were selected 12
Page 122 and 123: Uranium Miners 111
Page 124 and 125: 9 RADIATION EXPOSURE IN FLIGHT The
Page 126 and 127: DNA damage (a chemical change in DN
Page 130 and 131: of risk in the lowest dose groups,
Page 132 and 133: found elevated solid cancer risk wi
Page 134 and 135: preconception doses between 2.5 and
Page 136 and 137: Table 10-1. Preconception irradiati
Page 138 and 139: Preconception Exposures 127
Page 140 and 141: Tracheoesophageal fistula and conge
Page 142 and 143: cancer were both associated with th
Page 144 and 145: 0.10-4.71) while respiratory system
Page 146 and 147: elationship was not significant for
Page 148 and 149: times higher than in less-contamina
Page 150 and 151: Nuclear Power Accidents 139
Page 156 and 157: 12 COMMUNITIES NEAR NUCLEAR FACILIT
Page 158 and 159: levels (this could not in itself be
Page 160 and 161: Figure 12-3. Native Americans from
Page 162 and 163: of leukemia was measured over a lar
Page 164 and 165: (RR 1.06; 1.00-1.11) and risks of s
Page 166 and 167: more that we can say about this app
Page 168 and 169: Communities Near Nuclear Facilities
Page 176 and 177: 54 observed vs. 46.1 expected death
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13 DISCUSSION Our intention in crea
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myeloid leukemia) was significantly
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0.1-3.5 WLM; this is roughly equiva
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adon (Lubin et al. 1997). These res
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Leukemia Leukemia, a general term t
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vical cancer. The doses to these pa
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England have found it convenient to
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Thyroid disease Thyroid cancer is a
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1986 through 1995. These workers sh
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dence of this disease includes elev
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Analysis of preconception exposure
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Paternal age, education, drinking O
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Gardner et al. 1990 Employed at Sel
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we consider this group of a few hun
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Leukemia risk (excluding CLL) among
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Glossary of Terms for Epidemiology
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Glossary 199 Beta radiation: Stream
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Dosimetry: Measurement or estimatio
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Glossary 203 Hypothyroidism: The cl
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Glossary 205 Metastasis: 1. Movemen
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Glossary 207 waves, ultra violet (U
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Glossary 209 Thyroid Disease: disea
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Bibliography ATSDR. Public Health A
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Bhatia S, Sklar C. Second cancers i
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Bibliography 215 Cavallo D, Tomao P
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Bibliography 217 Department of Ener
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Bibliography 219 Gardner MJ, Hall A
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Haldorsen T, Reitan JB, Tveten U. C
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Bibliography 223 Howe GR, Nair R, N
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of Mayak, A comparison of numerical
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Bibliography 227 Laird NM. Thyroid
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control population. International J
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Bibliography 231 Neel JV, Schull WJ
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2003.160:381-407. Bibliography 233
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Bibliography 235 Saccomanno G, Auer
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Bibliography 237 analysis of cancer
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Bibliography 239 Tokarskaya ZB, Sco
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Journal of Epidemiology 1987.125(2)
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Actinium, 84 Acute lymphocytic leuk
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and Nevada Test Site, 60-61, 62 nuc
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Hashimoto’s thyroiditis, 185 Heal
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studies, 101-2 Medical exposure, 19
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(RERF), 43 Radiation Exposure Compe
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Viruses, 118, 154, 193 West Germany
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