Gwynedd & Anglesey, North Wales
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National Public Health Service for Wales Childhood Cancer Incidence – Gwynedd & Anglesey, North Wales Childhood Cancer Incidence – Gwynedd & Anglesey, North Wales Discussion report by the National Public Health Service for Wales Version:9 Date:09/03/2005 Status: Final Author: Andrew Jones. Environmental Page: 1 of 18 Public Health Team National Public Health Service for Wales Childhood Cancer Incidence – Gwynedd & Anglesey, North Wales Executive Summary Background and context In February 2004 the alleged existence of an increased risk of childhood cancers in areas of the North Wales coastline, linked to radiation discharges from the nuclear installation at Sellafield in Cumbria, was reported through the media. The media reports followed analysis of information and the subsequent release of a report by an organisation known as ‘Green Audit’. Having compared information from different sources for the period 1982-1990 and 2000-2003, the ‘Green Audit’ report claimed to identify evidence of a continuing increased risk of childhood leukaemia and other childhood cancers (brain/spinal and retinoblastoma) in the population living close to the Menai Straits. The National Public Health Service for Wales (NPHS) was asked to support the Local Health Boards in Gwynedd and Anglesey in investigating these latest claims. The NPHS requested the Welsh Cancer Intelligence and Surveillance Unit (WCISU) to examine relevant validated cancer registry information and then separately reviewed the findings, together with those released by ‘Green Audit’. This report summarises the findings of the NPHS review. WCISU have prepared a separate report which includes details of the technical analysis and tables of results. It should be noted that the issues raised by the ‘Green Audit’ report are not new. Similar claims in relation to the North Wales coast have been made previously by ‘Green Audit’. These previous claims have been thoroughly investigated by an independent expert advisory committee – the Committee on Medical Aspects of Radiation in the Environment (COMARE) as recently as 1999. No evidence was found to support allegations of increased risk of childhood cancers close to the North Wales coastline. A public statement has previously been made by COMARE to this effect. This conclusion has also been supported by a complete analysis which was published in 2001. Methodology and Limitations These latest claims made by ‘Green Audit’ have been investigated by examining validated cancer registry information. Where possible the methodology described in the ‘Green Audit’ report has been followed. In addition cancer registry data has been examined for the whole 22 year period 1982-2003. The NPHS wishes to highlight that there are limitations to undertaking studies on small geographical areas, which must be reflected in the methodology used and subsequent interpretation of results. Data accuracy is paramount when undertaking small area studies. The NPHS has been advised that in investigating this issue, Version:9 Date:09/03/2005 Status: Final Author: Andrew Jones. Environmental Page: 2 of 18 Public Health Team National Public Health Service for Wales Childhood Cancer Incidence – Gwynedd & Anglesey, North Wales WCISU has worked closely with the clinicians who treat children with cancer, so as to ensure that the data which has been used is as accurate as possible. The NPHS acknowledges that cancer registration is a dynamic process and that it can take several years for incidence rates to stabilise. Childhood cancer is relatively rare. WCISU and NPHS operate under strict legal and ethical guidelines which prevent the disclosure of information which may break patient confidentiality. For this reason the NPHS report does not contain details of the statistical data which has been analysed by WCISU. It is also difficult to comment in detail publicly on the findings of the ‘Green Audit’ report, as this relates to small populations and very small numbers of cases. Results and Conclusions The NPHS has reviewed the statistical analysis undertaken by WCISU to date. Following analysis of the cancer registry information for the period 1982–2003, no credible evidence has been found to support the findings of an increased risk of childhood cancer in the Menai Straits/Caernarfon area of North Wales as claimed in the ‘Green Audit’ report. A continuing trend of increased incidence of childhood leukaemia has not been demonstrated during the period. Similarly, rates for brain (and spinal) tumours and retinoblastoma in children within the study areas have not been found to be significantly different from expected. Weak evidence for a slightly raised risk of childhood leukaemia in the study areas has been found in the 2000-2003 period. This is however based on a very small number of cases, notably in relation to the smaller of the two study areas. This is not apparent in any previous period and is most likely a chance finding. No significant results have been found for childhood leukaemia in either the Anglesey or Gwynedd LHB populations for the 2000-2003 period or any previous period. NPHS and WCISU can see no reason for public concern in respect of this latest ‘Green Audit’ report. NPHS will continue to work with WCISU and other partners in the surveillance of LHB populations across Wales. Any unusual occurrences of cancer will be brought to the attention of the NPHS as a matter of routine. Additional Comments The NPHS wishes to point out that there are many limitations associated with studies based on small areas of population and great care is required in undertaking analysis and interpretation of results. Errors in the methodology, analysis and interpretation of results have been found whilst undertaking the review of the ‘Green Audit’ report. The Version:9 Date:09/03/2005 Status: Final Author: Andrew Jones. Environmental Page: 3 of 18 Public Health Team National Public Health Service for Wales Childhood Cancer Incidence – Gwynedd & Anglesey, North Wales report is based upon very small numbers of cases and appears to overestimate the level of risk and the statistical significance of results leading to the potential for unnecessary public concern. The NPHS strongly recommends that all organisations adopt accepted procedures and processes for ethical approval and scientific peer review, prior to carrying out studies and releasing information to the public. Such processes are essential in ensuring that errors/ deficiencies in study design/methodology/interpretation are identified prior to publication. The NPHS is aware that ‘Green Audit’ have previously received such a recommendation from COMARE following reviews of previous reports. Version:9 Date:09/03/2005 Status: Final Author: Andrew Jones. Environmental Page: 4 of 18 Public Health Team National Public Health Service for Wales Childhood Cancer Incidence – Gwynedd & Anglesey, North Wales 1. Background In February 2004, televisioni and newspaperii reports appeared in the Welsh media referring to the existence of a ‘cluster’ of childhood cancers (leukaemia, brain cancer and retinoblastoma) along a section of the North Wales coastline and linking them to radiation releases from the Sellafield nuclear reprocessing plant in Cumbria. The reports followed investigation by media researchers and subsequent analysis of information and production of a reportiii by the organisation ‘Green Audit’. The NPHS wishes to point out that the methods used in this report do not appear to have been subject to ethical approval, and there was apparent no peer review process undertaken prior to the release of information into the public domains Following the initial allegations, a press release was issued by the Welsh Cancer Intelligence and Surveillance Unit (WCISU) (Appendix 1), which made clear that the questions raised by the report were not new and that investigations to date by WCISU and the Committee on Medical Aspects of Radiation in the Environment (COMARE) had not yet found any significant support for similar claims made previously by ‘Green Audit’. Following the media coverage, neither Gwynedd nor Anglesey Local Health Board reported receiving any requests for information from local communities. The Welsh Assembly Government, on receiving correspondence from the local Assembly Member for Caernarfon, requested the National Public Health Service for Wales to assist the Local Health Boards of Gwynedd and Anglesey by coordinating a response to the alleged findings. This short discussion document puts the subject in context and summarises the action taken to date. 2. Context Claims of increased childhood cancer incidence in North Wales are not new. A report previously released by ‘Green Audit’ made similar claims of increased childhood cancer risks across the North Wales coast. This reportiv, together with a report prepared by WCISUv (which did not support such conclusions), were reviewed by COMARE, who issued a statementvi concluding that they had found no evidence to support the contention that there was an increased incidence of childhood leukaemia or other cancers close to the North Wales Coast. This conclusion was supported by a complete analysis, which was published by Steward et al vii in 2001. The COMARE statement concluded that ‘Green Audit’ had used incorrect data and requested the authors to withdraw the conclusions of the analysis, which had given rise to considerable public concern. Version:9 Date:09/03/2005 Status: Final Author: Andrew Jones. Environmental Page: 5 of 18 Public Health Team National Public Health Service for Wales