A review of studies of childhood cancer and natural background radiation

Abstract

Purpose

The projected existence and magnitude of carcinogenic effects of ionizing radiation at low doses and low-dose rates is perhaps the most important issue in radiation protection today. Studies of childhood cancer and natural background radiation have the potential to throw direct light on this question, into a dose range below a few tens of mSv. This paper describes the studies that have been undertaken and their context, discusses some problems that arise and summarizes the present position.

Conclusions

Many such studies have been undertaken, but most were too small to have a realistic chance of detecting the small effects expected from such low doses, based on risk projections from higher exposures. Case–control or cohort studies are to be preferred methodologically to ecological studies but can be prone to problems of registration/participation bias. Interview-based studies of the requisite size would be prohibitively expensive and would undoubtedly also run into problems of participation bias. Register-based studies can be very large and are free of participation bias. However, they need to estimate the radiation exposure of study subjects using models rather than individual measurements in the homes of those concerned. At present, no firm conclusions can be drawn from the studies that have been published to date. Further data and perhaps pooled studies offer a way forward.

Keywords:

• Background radiation
• cancer
• epidemiology

Acknowledgements

We are grateful to numerous colleagues for their helpful discussions, most particularly to the authors of the earlier reviews that we cite. The two anonymous referees made helpful suggestions.

Disclosure statement

Richard Wakeford receives a consultancy fee as a member of the Technical Working Party of the Compensation Scheme for Radiation-linked Diseases (http://www.csrld.org.uk). Dr Kendall and Dr Little report no conflict of interest.

Additional information

Funding

The Intramural Research Program of the National Institutes of Health, the National Cancer Institute, Division of Cancer Epidemiology and Genetics supported the work of MPL.

Notes on contributors

Gerald M. Kendall

Gerald M. Kendall, PhD, worked for thirty years at the then UK National Radiological Protection Board. When he retired in 2005 he became an honorary senior research fellow at the Childhood Cancer Research Group, Oxford University. He is now a visitor in the Cancer Epidemiology Unit within the Nuffield Department of Population Health. His research interests are in the area of childhood cancer and ionising radiation, most particularly a large record-based study of childhood cancer and natural radiation. He has published widely in the peer-reviewed literature.

Mark P. Little

Mark P. Little, DPhil, joined NCI Radiation Epidemiology Branch (REB) in 2010, and was promoted to a Senior Investigator in 2012. Previously (2000–2010), he worked in Imperial College London, and before that (1992–2000) at UK National Radiological Protection Board (now part of Public Health England). He is a member of Council of NCRP, and has served as consultant to UNSCEAR, to IAEA, to ICRP (in particular as member of ICRP Task Group 91), to the UK COMARE, and to NCRP SC 1-21 and 1-26. In REB, Dr. Little is working on assessment of leukaemia risk in persons exposed at low doses and dose rates, cancer risk in various groups exposed as result of the Chernobyl accident, on risks of various health endpoints in the US radiologic technologists, and on treatment-related second cancer risks in various populations. He has particular statistical interests in machine learning algorithms and dose measurement error models. He has over 280 publications in the peer-reviewed literature.

Richard Wakeford

Richard Wakeford, PhD, before retiring at the end of 2019 was Professor in Epidemiology in the Centre for Occupational and Environmental Health of The University of Manchester, United Kingdom. He is now an Honorary Professor in the Centre.