HSE Investigation of Leukaemia and other cancers in the children of male workers at Sellafield ld7 (nN 22501858335 Health & Safety Executive HSE Investigation of Leukaemia and other cancers in the chiidren of male workers at Sellafield X~OC INFORMS TI"! QENTRE HSE BOOKS vl 19 APR 1994 | Wellcome Centre for Medical Science © Crown copyright 1993 Applications for reproduction should be made to HMSO First published 1993 ISBN 0 7176 06597 CONTENTS ACKNOWLEDGEMENTS __ iv BACKGROUND TO HSE INVESTIGATION / INTRODUCTION TO THE HSE STUDIES 3 Aims and contribution of each study 3 Development of investigation protocol 4h Overall study management arrangements 5 THE CASE-ONLY STUDY 7 Objectives 7. Working methods 8 Findings of the case-only study 8 THE RADIATION DOSE STUDY 10 Objectives lO Working methods 10 Findings of the radiation dose study 14 MAIN CASE-CONTROL STUDY /5 Objectives and overall plan 15 identification of cases and controls 16 Extraction of information and production of dossiers 19 Statistical methods 23 Findings of the case-control study 28 DISCUSSION 47 The Case-only Study 47 The Radiation Dose Study and the main Case-control Study 47 CONCLUSIONS 54 REFERENCES 57 GLOSSARY 59 APPENDICES 1 Case-control study - identification of cases and controls 6/7 2 Data extraction 87 3 Statistical methods, definition of variables and detailed Results 109 ACKNOWLEDGEMENTS The Health and Safety Executive wishes to acknowledge the help provided by the following organisations and individuals, without whose co-operation, assistance and advice this investigation would not have been possible. Professor M Gardner, who provided valuable advice and assistance before his untimely death. The managements and workforces of British Nuclear Fuels ple and the United Kingdom Atomic Energy Authority, in particular; Mr K Binks, Dr A Britcher, Mr B Carpenter, Mrs M Frost, Dr A Slovak, Dr R Strong, Dr R Wood, Mr J Wraight. The Office of Population Censuses and Surveys, in particular; Dr J Fox; Mrs D Lewis, Mr J Davies and other staff in the Registration Division; and Mrs E Lea and staff in the Medical Research Section. Staff at the North Western, Mersey, Thames, Oxford, and South Western Regional Cancer Registries. Staff at the National Radiological Protection Board, in particular; Dr M R Bailey and Dr G Etherington. Professor V Beral Professor N Day Dr G Draper Mr C Stiller Dr A Craft Dr L Parker Mr B Pannett Dr R Sharpe Professor G Harnden Dr D Goodhead Dr E Wright Mr M Russell who provided data on the frequency of forenames. The authors of this report would also like to thank all the HSE clerical and secretarial staff involved, particularly Mrs A Hill and Mrs E Morris, and the staff in HSE’s Directorate of Information and Advisory Services, for their contribution to the investigation and with the compilation of this report. The investigation was carried out under the direction of Mr EJ Varney, Deputy Chief Inspector, Nuclear Installations. The main epidemiological case-control study was designed by Mr J T Hodgson, and the project was controlled through a Steering Committee with members as follows: Mr EJ Varney Mr J T Hodgson Dr J Osman Dr R McCaig Mrs S J Hutchings Mr L G Williams Mr BJ Furness Mr K Smith The work was carried out by the following: Team A1: Identification of candidate cases and controls: analysis of radiation dose study Dr R McCaig Mrs S J Hutchings Team A2: Matching of candidate cases and controls to the Sellafield workforces and preparation of dossiers Mr J S Griffiths Mr J Sandford Mr H K Robinson MissJ A Gibbs Mr I Johnson Miss S Dee Miss M Jennings Mr D A Adams Mr R Comaish Mr S A Bridge Miss L Blundell Team B: Assessment of external radiation dose for study subjects Mr K Smith Mr L Bevington Mr P Burrows Mr M Leach Mr D Brown Mr I F Robinson Mr D Marshall Team C: Assessment of potential chemical exposures Dr M Tew Mr J Lindsay Mrs J Rutherford Mr P Watson Mr D Daniels Mr W Thompson Dr R Elliot Team D: Data preparation and statistical analysis Mr J Hodgson Miss K Naylor Mr A Sweeney Miss G Grocott Mr S Clark Miss V Boardman Mrs K Hall Miss A Turpin BACKGROUND TO HSE INVESTIGATION 1 In November 1983, Yorkshire Television broadcast a programme: “Windscale - The Nuclear Laundry”. It suggested that in the village of Seascale, 3 km south of Sellafield, there was an excess of childhood leukaemia, and implied that this was due to the radioactive discharges from the plant. 2 Following the screening of the programme, the Minister of Health commissioned an independent advisory group chaired by Sir Douglas Black to investigate the claim. The Group published its findings’ in 1984. These included a review of earlier work which indicated that there was an excess of leukaemia in children in Seascale, but that for West Cumbria as a whole, the mortality from childhood cancer was near the national average. It concluded, inter alia, that the calculated radiation doses to young people in Seascale did not support the view that the radioactivity released from Sellafield* was responsible for the observed incidence of leukaemia in Seascale and its neighbourhood. 3 The Group recommended that epidemiological studies and research should be carried out on the subject, and that a specialist body with significant health representation should be set up to advise on the control of permitted radioactive discharges. This led to the setting up by the Minister for Health of the Committee on Medical Aspects of Radiation in the Environment (COMARE) in November 1985. Its terms of reference were “to assess and advise government on the health effects of natural and man-made radiation in the environment and to assess the adequacy of the available data and the need for further research”. 4 Professor Gardner, of the Medical Research Council Environmental Epidemiology Unit, was a member of Sir Douglas Black’s Advisory Group, later becoming a member of COMARE: he was one of a number of people who followed up the Group’s recommendation for further research. Professor Gardner set up a number of investigations including an epidemiological case-control study to examine the observed excess of childhood leukaemia and lymphoma near Sellafield in relation to certain behavioural or lifestyle variables (including those that might affect individual uptake of environmental radioactivity), and to radiation received during fathers’ employment at the Sellafield nuclear plant. 5 Using a variety of sources, the study identified 52 cases of leukaemia and 22 cases of non-Hodgkin’s lymphoma (NHL) in children who had been born and diagnosed of These discharges were later reassessed in a report’ issued by COMARE their illness in West Cumbria. Through the use of questionnaires and other methods, comparing the cases with other children as controls, the Gardner team examined the relative risks associated with various factors including paternal preconception radiation dose, maternal abdominal X-rays in pregnancy, paternal and maternal ages, maternal viral infection during pregnancy, family eating and children’s play habits, paternal occupation and proximity of residence to Sellafield. The results of the study’ were published on 15 February 1990. None of these potential explanatory factors showed any significant association with childhood leukaemia except fathers’ pre- conception radiation dose. Professor Gardner concluded that: “The raised incidence of leukaemia, particularly, and non-Hodgkin’s lymphoma among children near Sellafield was associated with paternal employment and recorded external dose of whole body penetrating radiation during work at the plant before conception. The association can explain statistically the observed geographical excess.” The highest relative risks* recorded were of the order of sixfold for fathers with total radiation doses of 100 mSv or greater before the date of their child’s conception, or doses of 10 mSv or greater during the six months before conception. The publication of this report caused considerable public and political interest. Discussions were held between the Department of Health and the Health and Safety Executive (HSE) to determine what action should be taken. It was clear that the Gardner findings suggested a possible occupational cause which was a matter that HSE should pursue, and it was agreed that HSE would carry out an investigation into occupational factors arising at Sellafield which might shed further light on these findings. The Health Minister announced the start of this investigation on 15 February 1990%. A group was formed for this purpose with staff drawn from HSE’s Nuclear Installations Inspectorate (NII) and the Epidemiology Unit of its Health Policy Division (which now forms part of the Technology and Health Sciences Division, THSD). The term "relative risk" in this report means the ratio of the probabilities that a case will occur in one group compared to another. In case-control studies, the relative risk is estimated by the “odds ratio" (OR): this i6 the ratio of the odds that a case will occur in one group compared to another.