Sources, Effects and Risks of Ionizing Radiation
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SOURCES, EFFECTS AND RISKS OF IONIZING RADIATION United Nations Scientific Committee on the Effects of Atomic Radiation UNSCEAR 2016 Report to the General Assembly, with Scientific Annexes UNITED NATIONS New York, 2017 NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Seventy-first Session, Supplement No. 46 and corrigendum (A/71/46 and Corr.1). The report reproduced here includes the corrections of the corrigendum. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. UNITED NATIONS PUBLICATION Sales No. E.17.IX.1 ISBN: 978-92-1-142316-7 eISBN: 978-92-1-060002-6 © United Nations, January 2017. All rights reserved, worldwide. This publication has not been formally edited. Information on uniform resource locators and links to Internet sites contained in the present publication are provided for the convenience of the reader and are correct at the time of issue. The United Nations takes no responsibility for the continued accuracy of that information or for the content of any external website. Corrigendum to Sales No. E.17.IX.1 18 May 2018 Sources, Effects and Risks of Ionizing Radiation: UNSCEAR 2016 Report to the General Assembly, Scientific Annexes A, B, C and D Corrigendum Annex D, page 438, paragraph 319, last line should read (18.6 mBq/d) and not (18.6 mBq/L) V.18-03158 *1803158* ANNEX D BIOLOGICAL EFFECTS OF SELECTED INTERNAL EMITTERS—URANIUM 361 ANNEX D: BIOLOGICAL EFFECTS OF SELECTED INTERNAL EMITTERS—URANIUM 363 CONTENTS I. INTRODUCTION ................................................................................................................................. 365 II. SOURCES AND LEVELS .................................................................................................................... 367 A. Natural sources .......................................................................................................................... 367 B. Artificial sources ........................................................................................................................ 374 III. PHYSICAL, RADIOLOGICAL AND CHEMICAL CHARACTERISTICS ..................................... 378 A. Physical and radiological characteristics .......................................................................... 378 B. Chemical characteristics ......................................................................................................... 379 IV. HUMAN EXPOSURE .......................................................................................................................... 380 A. Exposure of members of the public ................................................................................... 380 B. Occupational exposure .......................................................................................................... 382 C. Measurement of uranium ...................................................................................................... 382 V. BIOKINETICS ........................................................................................................................................ 383 A. Inhalation ..................................................................................................................................... 384 B. Ingestion ...................................................................................................................................... 385 C. Absorption .................................................................................................................................. 386 D. Systemic distribution, retention and excretion ............................................................. 386 E. Materno-fetal transfer ............................................................................................................. 387 VI. DOSIMETRY ......................................................................................................................................... 388 VII. BIOLOGICAL EFFECTS ...................................................................................................................... 390 A. Chemical versus radiological toxicity ................................................................................ 390 B. Kidneys ......................................................................................................................................... 391 C. Bone ............................................................................................................................................... 397 D. Lungs ............................................................................................................................................. 399 E. Liver ............................................................................................................................................... 400 F. Brain ............................................................................................................................................... 401 G. Reproduction and development ........................................................................................ 405 H. Other organs .............................................................................................................................. 408 I. Relative biological effectiveness ......................................................................................... 414 J. Lethal effects .............................................................................................................................. 414 364 UNSCEAR 2016 REPORT VIII. EPIDEMIOLOGICAL STUDIES ......................................................................................................... 416 A. Studies of occupational exposure ...................................................................................... 416 B. Studies of Gulf War veterans ................................................................................................ 433 C. Studies of environmental exposure ................................................................................... 434 IX. RESEARCH NEEDS ............................................................................................................................. 437 X. GENERAL CONCLUSION ................................................................................................................. 438 XI. ACKNOWLEDGEMENTS .................................................................................................................. 439 APPENDIX A. TABLES SUMMARIZING URANIUM LEVELS IN WATER, STUDIES OF OCCUPATIONAL AND ENVIRONMENTAL EXPOSURE TO URANIUM ...................................... 441 REFERENCES ............................................................................................................................................... 467 ANNEX D: BIOLOGICAL EFFECTS OF SELECTED INTERNAL EMITTERS—URANIUM 365 I. INTRODUCTION 1. This annex provides a review of the scientific literature on characteristics of uranium, its biokinetics and dosimetry within the human body for various physical and chemical forms and routes of intake into the body, radiobiological and toxicological effects of exposure to uranium, and epidemiological studies of nuclear workers and the public who have been exposed to uranium. 2. Uranium was discovered by Martin Heinrich Klaproth in 1789 and its radioactive properties by Antoine Henri Becquerel in 1896. Uranium, element 92 in the periodic table, is present naturally in all rock and soil. Levels of uranium content in soil depend on local geology and range widely from a few mg/kg up to levels of several per cent in ore bodies. The Committee in its UNSCEAR 2008 Report [U10] reported a median activity concentration of around 30 Bq/kg (1.2 mg/kg) for uranium in rock and soil. Uranium is released to the environment through natural events such as forest fires and volcanoes and released from rock and soil through natural processes. It is distributed through mechanisms such as leaching to ground and surface water and through wind erosion of soil. In turn, uranium in water, soil and air is taken up by plants and animals. People may be exposed to uranium by inhalation of airborne particulates, through skin uptake and through ingestion of uranium in food and water. 3. There are three naturally-occurring, alpha-particle emitting, isotopes of uranium: 238U, 234U and 235U. Two of these, 238U and 235U, with radioactive half-lives of 4.47 × 109 and 7.04 × 108 years respectively, are the parents of radioactive decay chains that are major contributors to the background radiation exposure of the human population. Uranium-238 supports 14 decay products. The isotope 234U, with a half-life of 2.45 × 105 years, is a member of the 238U decay chain. In natural uranium, 238U is the most abundant isotope in terms of mass (99.2742%), while 234U and 235U constitute only 0.0054% and 0.7204%, respectively [N8, S15]. Figure I shows a simplified