Assessment of Radiation Exposure in the National Cohort

URN: urn:nbn:de:101:1-201309164745

A project sponsored by the Helmholtz Association, the German Federal Ministry of Education and Research (BMBF) and the German Länder plans to establish a National Cohort that will provide data for epidemiological studies of the influence of environmental factors and lifestyle on the development of disease. It is envisaged that two hundred thousand participants will be recruited for the cohort. The National Cohort may help to provide information on two key issues relating to protection against ionizing radiation.

The SSK recommends retrospective and prospective recording of the organ doses of members of the National Cohort as a result of medical, occupational and external natural radiation exposure for the following reasons. The study has the potential:

• to provide information about the distribution of medical exposure.
• to measure the level and distribution of natural external exposure.
• to collect data on medical, occupational and natural exposure for each individual cohort member that is not available in any other existing cohort.
• to provide an estimate of the upper limit of the confidence interval of the risk from doses that reflect the variability of doses from all exposure to ionizing radiation (except radon) in the German population.
• o create a dataset with a wide range of behavioural and health parameters that in combination with exposure information could be very useful for future investigations.

In view of the open questions that have been described in relation to

• validation of the reconstruction of medical exposure,
• the expected dose distribution among cohort members, which is key to the statistical usefulness of the study,
• the uncertainty of the dose estimates and their impact on the risk assessment

the SSK recommends that the next step should be to use the baseline assessment of the National Cohort for a larger feasibility study (several thousand participants) of the determination of organ doses from medical use of ionizing radiation and from occupational, natural and technologically enhanced radiation exposure. The information on medical radiation exposure provided by cohort members should, for example, be validated against data held by providers of statutory health insurance. To reconstruct the exposure of people with higher levels of medical exposure, medical records should also be evaluated. X-ray record cards should be issued as part of the feasibility study; during follow-up their use should be checked and reminders issued. The uncertainties about dose distribution that arise because radon exposure is not measured and data on internal exposure as a result of food consumption is not collected should be taken into account when analysing the data. It is worth investigating whether questions about building characteristics can be asked in such a way that collection of information on radon exposure becomes possible. Consideration should also be given to collecting some basic information on radiation exposure for all 200,000 cohort members at the time of the baseline assessment. Finally, the costs and benefits of capturing radiation exposure in the entire cohort should be discussed.

The later assessment of radiation exposure in the entire National Cohort during the follow-up investigation would then have the advantage that the procedure used would have been validated. For the subgroup investigated in the feasibility study, the time history of medical and natural external radiation exposure can be determined.

The SSK also recommends that other European countries be encouraged to collect information on radiation exposure in their national cohorts with a view to later pooling of the data. Cooperation with other large European cohorts (UK: 500,000, SE: 500,000, FR: 200,000, NL: 160,000) could provide a broader statistical basis with more than one million participants and potentially make a genuine risk assessment possible rather than simply an estimate of the upper limit of the confidence interval.