HPA response statement: Advisory Group on Ionising Radiation's report on circulatory disease risk

HPA welcomes the Advisory Group on Ionising Radiation (AGIR) report on Circulatory Disease Risk.  All members involved in writing the report are thanked for their diligent and thorough work in reviewing a complex area.   The report makes seven recommendations as set out below and the HPA response to each is given following each recommendation.

1. There are multiple contributory risk factors to circulatory disease, including genetic, environmental and lifestyle factors.  HPA should continue to advocate avoidance of these risk factors where possible to minimise the incidence of such diseases in the population and to reduce the impact of any synergies with radiation.
   HPA provides general health protection advice when considering radiation specifically, a good example being avoidance of tobacco smoking to reduce risk of radon associated lung cancer.  Such an approach will be adopted in provision of advice by the HPA Centre for Radiation, Chemical and Environmental Hazards (CRCE) should evidence accrue that  circulatory disease is caused by  low doses of radiation.
   
2. Given the evidence for radiation of critical vasculature at high and very high doses leading to health problems, notably heart disease and stroke, AGIR recommend that HPA encourage medical practitioners who deliver radiation for either therapeutic or diagnostic purposes and their professional associations to examine current practice with a view to minimising radiation of critical vasculature while maintaining effective clinical outcome and to consider a follow up programme for exposed patients to improve estimation of risk.
   The Medical Exposure Department of CRCE is engaged in work on modelling of radiation doses to tissues as a consequence of diagnostic examinations; data on average doses delivered in UK practice are also gathered and collated.  In their work and engagement with radiotherapy units and professional bodies, staff will encourage the examination of current practice, consistent with the AGIR recommendations.  Copies of the AGIR report will be sent to the relevant professional bodies.
   
3. The uncertainties on radiation causality of atherosclerotic disease are likely to be reduced only when an improved understanding of the impact of radiation at different dose levels on the development, destabilization and rupture of atherosclerotic plaques is available.  Many processes such as cell senescence, cell death, thrombosis, mitochondrial dysfunction, inflammation and fibrosis are implicated in atherogenesis and are also induced by radiation exposure.  AGIR note that atherogenesis in rodent models and humans has important differences as well as significant similarities.  AGIR recommend HPA develop research to improve mechanistic understanding of the impact of radiation on atherosclerotic plaque formation and destabilization, where possible using human systems.
   The Biological Effects Department of CRCE has recently started a research project  on the impact of radiation exposure on atherosclerotic plaque development using an in vitro human cell model system and work will be coordinated with international initiatives on radiation-induced circulatory disease. 
   
4. Biomarkers of circulatory disease risk are not, in general, well developed; any research that might identify such markers should be encouraged by HPA.  Such biomarkers would be of value in establishing whether radiation is causal for circulatory disease.  These biomarkers could be biochemical, cellular or physiological.  Imaging methods to assess vascular function might be especially useful as non-invasive techniques.
   The Biological Effects Department at CRCE  will keep biomarker research under review and consider developing appropriate research projects on the basis of such markers.
   
5. AGIR recommends that in retrospective health risk assessments of individuals exposed to doses of 0.5Gy and above, consideration of circulatory disease risk should be included.
   HPA agrees with this recommendation.
   
6. In anticipation of the possible future emergence of evidence for radiation causality of circulatory disease below 0.5 Gy, AGIR recommends HPA considers the implications of such evidence for radiation protection. 
   This issue is being discussed by CRCE staff internally and in the context of contributions to international level advice, notably to ICRP. 
   
7. Further follow-up of the atomic bomb survivors and various occupationally-exposed groups (e.g., nuclear workers, Chernobyl liquidators) is strongly recommended, and is likely to be increasingly informative of risks at moderate and low doses. 
   HPA CRCE is leading an epidemiological  study of UK nuclear workers, the National Registry for Radiation Workers, which includes analysis of risks of non-cancer diseases.  CRCE is also participating in collaborative research on cancer and  non-cancer diseases in workers at the former Soviet Union Mayak plant that produced plutonium for atomic weapons.

HPA recognises the importance of research to improve our understanding of the risks of radiation-induced circulatory disease and will collaborate in epidemiological and experimental studies to quantify risks and determine mechanistically whether risks apply at low doses. HPA will keep this topic under review and will anticipate any requirement for inclusion of circulatory disease in risk estimates at doses below 0.5 Gy.

Last reviewed: 8 October 2010