Bølviken, B. (ed.): Natural Ionizing Radiation and HealthProceedings from a symposium held at the Norwegian Academy of Science and Letters, Oslo 67 June 2001 Preface This book contains a collection of papers presented at the symposium "Nat ural Ionizing Radiation and Health" held in Oslo June 5 6, 2001. The meeting was number 13 in a series of symposia organized from 1980 on by the Com mittee for Geomedicine of the Norwegian Academy of Science and Letters. Since 1986 these symposia have been arranged in