[ RadSafe ] HPA Press Stament on (COMARE)'s Tenth Report]

[Marcel Schouwenburg]

News from the UK.

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Press Statement 

http://www.hpa.org.uk/hpa/news/articles/press_releases/2005/050610_childhood_cancer_nuclear.htm

10 June 2005

The incidence of childhood cancer around nuclear installations in Great Britain 

The Health Protection Agency (HPA) welcomes the Committee on Medical Aspects of Radiation in the Environment (COMARE)'s Tenth Report, an investigation into the incidence of childhood cancer around nuclear installations in Great Britain. The report uses advanced statistical techniques to see whether there are unusual aggregations (usually called clusters) of childhood cancer around these sites.

There have been several reports of clusters of childhood cancer around nuclear installations and HPA is concerned to understand the reasons for these. Attention has often concentrated on leukaemia, the most common childhood cancer, and sometimes on both leukaemia and the related disease, non-Hodgkin lymphoma (collectively referred to as "LNHL").

The average number of cases of childhood cancer to be expected in an area over a specified time period can be calculated based on the size of the population. If many areas are examined, then in certain localities the number of cases observed will be somewhat greater than the number expected on average simply by chance, and the frequency with which this will happen can also be calculated. However, earlier research (Draper et al, 1991) has indicated that more clusters of LNHL are found than would be expected on the basis of chance alone. These clusters are found all over the country, not only near certain nuclear installations. A future COMARE report will examine the geographical distribution of childhood cancer in detail.

The way that the extra clusters (those over and above those that would occur by chance) are distributed is complicated. Clustering can occur over a particular scale of distance or time - for example over a few miles rather than tens of miles or over a few years rather than tens of years. Moreover, there may be different types of clusters in different regions (e.g. counties). The new report uses sophisticated ways of investigating whether such clusters arise around nuclear installations. These statistical tests are sensitive both to a general increase in cancer in the area studied and to any tendency for rates to increase with proximity to the installation itself. Different statistical tests were selected as the most appropriate for different sites, based on their statistical power to detect trends in risks.

Using these techniques, the new report found no evidence for raised rates of LNHL or of other childhood cancer within 25 km of nuclear power stations. 

For other nuclear installations, increased rates of LNHL were confirmed around Burghfield, Dounreay and Sellafield. There was evidence which reached statistical significance of a tendency for LNHL rates to increase with increasing proximity to Rosyth, with borderline suggestions of a similar trend around Capenhurst. In both instances there was no evidence of an increased incidence in the general locality. COMARE noted that another published study (Sharp et al, 1996) using similar methods had not found an increase of LNHL near Rosyth and recommended that the reasons for the discrepancy should be investigated.

So far as other childhood cancers are concerned, there were raised incidence rates around the neighbouring sites Aldermaston, Burghfield and Harwell and also around Rosyth. COMARE suggests that the findings may largely reflect raised rates of solid cancers in these general areas. 

It is impossible for statistical tests to distinguish those clusters which arise solely because of the play of chance from the clusters which arise because of some specific cause. Extensive investigations have suggested that radiation doses from nuclear discharges are much too low to account for the extra cases of childhood cancer in the observed clusters (COMARE Fourth Report, 1996; Darby and Doll, 1987). Some investigations have provided support for a mechanism involving population mixing. A recent publication (Gilham et al, 2005) has provided support for the idea that lack of early exposure to infections may increase the risk of childhood leukaemia. However, it is likely that a number of factors are important.

The HPA supports further investigations around Rosyth and looks forward to the COMARE Eleventh Report which will investigate clustering of childhood cancer across the whole of Great Britain rather than specifically around nuclear installations. This will allow a better understanding of this complex question.

References

Committee on the Medical Aspects of Radiation in the Environment (COMARE) (2005). Tenth Report. The incidence of childhood cancer around nuclear installations in Great Britain. Downloads available from www.comare.org.uk and hard copies are available from the Information Office at the Health Protection Agency at Chilton. ISBN: 0-85951-561-3 (£13.50).

Committee on the Medical Aspects of Radiation in the Environment (COMARE) (1996). Fourth Report. The incidence of cancer and leukaemia in young people in the vicinity of the Sellafield site, West Cumbria: further studies and an update of the situation since the publication of the Black Advisory Group in 1984. Department of Health, London.

Darby S C and Doll R (1987). Fallout, radiation doses near Dounreay, and childhood leukaemia. 
BMJ, 294, 603-7.

Draper G J (ed) (1991). The geographical epidemiology of childhood leukaemia and non-Hodgkin lymphomas in Great Britain, 1966-83, Studies on Medical and Population Subjects No.53, OPCS, HMSO, London.

Gilham C, Peto J, Simpson J, et al. (2005). Day care in infancy and risk of childhood acute lymphoblastic leukaemia: findings from UK case-control study. BMJ, 330, 1294. 
This paper is available at http://bmj.bmjjournals.com/cgi/content/full/330/7503/1294?ehom

Sharp L, Black R J, Harkness E F and McKinney P A (1996). Incidence of childhood leukaemia and non-Hodgkin lymphoma in the vicinity of nuclear sites in Scotland, 1968-93. Occup Environ Med, 53, 823-831.


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