HC Deb 16 June 1994 vol 244 cc656-7W

Investigation of the Incidence of Cancer around Wylfa and Trawsfynydd Nuclear Installations

Background A detailed investigation of the incidence of cancer around the Trawsfynydd and Wylfa nuclear installations has been undertaken by the Welsh Cancer Registry. The study has now been published.

The Study The object of the study was to investigate the incidence rates from 1974–1986 of the following groupings of cancer: all leukaemias, lymphoid leukaemia, all lymphomas, Hodgkin's disease, multiple myeloma, brain cancer and thyroid cancer. These cancers were selected because of their suggested links with radiation in the medical literature at the time the study was undertaken. The geographical regions were defined as the pre-1974 local authority areas within Gwynedd. The time span was the years for which data were available from the Welsh Cancer Registry. Data were analysed by Stone's method for all ages combined and further analyses of lymphoid leukaemia and thyriod cancer were undertaken for three age groups (0–24 years, 25–64 years and 65 years and over).

Results

  1. (i) For both Trawsfynydd and Wylfa no significant results were found for all leukaemias, all lymphomas, Hodgkin's disease, multiple myeloma, brain cancer or thyroid cancer.
  2. (ii) The analysis of lymphoid leukaemia was undertaken separately for acute lymphoblastic leukaemia (ALL) and chronic lymphocytic leukaemia (CLL). However, in attempting to undertake these analyses account had to be taken of the approximately 9 per cent. of registrations which were recorded neither as ALL (ICD code: 204.0) nor CLL (ICD code: 204.1) but as 'other and unspecified lymphoid leukaemia' (ICD codes: 204.2, 204.8 and 204.9). It was not possible to determine the type of lymphoid leukaemia for such cases and therefore the analysis was undertaken in two ways, either with the cases recorded as unspecified lymphoid leukaemia analysed as if they were all ALL or with the cases recorded as unspecified lymphoid leukaemia analysed as if they were all CLL;
The results analysed in these two ways were as follows:

Acute Lymphoblastic Leukaemia (ALL)

  1. (a) Trawsfynydd. No significant results were obtained.
  2. (b) Wylfa. No significant results for ALL were found for all ages and in the age groups 0–24 and 25–64. If the single case of unspecified lymphoid leukaemia was included as ALL a significant result was obtained in the age group 65 and over (P=0.027, two cases observed in the area containing Wylfa compared to 0.25 expected).

Chronic Lymphocytic Leukaemia (CLL)

  1. (a) Trawsfynydd. No significant results were obtained for CLL when analysis was undertaken for all ages and for the age group 65 and over. Considering the age group 25–64 four cases were observed in the 657 area containing the installation compared to 0.57-0.66 expected with the relative risk decreasing as the distance from Trawsfynydd increased (p< 0.01).
  2. (b) Wylfa. No significant results were obtained.
(iii) Data for 1987 and 1988 became available during the period of the study. No further cases of lymphoid leukaemia were recorded in the local authority areas containing either installation.

COMARE'S ADVICE TO GOVERNMENT

COMARE considered and welcomed this study.

The Committee endorsed the statistical methods used.

In interpreting the results on ALL at Wylfa, the Committee noted that the statistically significant increase in ALL rests on a single case of unspecified leukaemia being included as acute lymphoid leukaemia rather than chronic lymphoid leukaemia. It was considered that this finding could be disregarded for the following reasons: Statistical associaton based on a single case is extremely unreliable. Placing weight of opinion on a finding based on reclassification of a case of unspecified leukaemia to ALL in the 65 years and over age group was felt to be unreasonable, since in this age group chronic leukaemia is very much more common than acute leukaemia.

Equally, the finding of cases of CLL around Trawsfynydd should not give rise to public concern because: The overwhelming weight of evidence from international studies leads to the conclusions that CLL is a leukaemia sub-type which has not been shown to be associated with, or induced, by ionising radiation. This fact alone should be sufficient to allay concern that environmental radiation might have played a part in causing such cases observed in this study. CLL is an indolent disease, predominantly of the elderly, which may cause few symptoms over long periods. Diagnosis is often the result of investigation of an unrelated complaint and incidence in a geographical area depends on the intensity of such investigations. Hence the baseline incidence is uncertain, particularly for relatively small areas and it is unwise to calculate rates, raised or otherwise, in subgroups in such areas. Given the number of statistical tests undertaken on this body of data there is a strong likelihood that at least one subgroup will show a statistical association by chance.

The Committee noted the considerable effort that had been made to confirm the diagnosis in the cases investigated. Further research to establish the diagnosis with greater certainty was not felt to be justified.

The Committee concluded that the study demonstrated no association between the incidence of the cancers studied and residence near Trawsfynydd and Wylfa nuclear stations. No further work to investigate such an association is recommended.

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