NAG meeting: February 2010: New Studies on the Impact of Low Level Radiation

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NAG's guest at our Spring meeting was Dr Ian Fairlie, an independent consultation on radiation and the environment, who spoke about new research work on the impacts of low-level radiation, and particularly the recent German study 'Kinderkrebs in der Umgebung von KernKraftwerken ' (KiKK).

Despite substantial interest in childhood leukemia clusters around nuclear sites at Dounreay, Windscale, and Burghfield in the 1980s and 1990s, there has been little debate on this issue in recent years. However, the KiKK study has re-ignited the controversy over the link between child cancers and nuclear installations. The study was commissioned by the German government and used case-controlled studies to investigate the incidence of cancer near nuclear reactors. It was conducted using a robust methodology by a team of pro-nuclear epidemiologists, and demonstrated a strong linkage between the risk of infant leukemias and solid cancers in babies and distance of place of residence from a nuclear reactor.

Although these results confirm the findings of a range of earlier studies, its thoroughness leaves little room for disagreement with the conclusions. Dr Fairlie likened the study to the epidemiological equivalent of Galileo's discovery that the earth rotates around the sun – with the nuclear establishment finding it as difficult to accept the findings as the Church did with Galileo's.

The study discounted confounding factors, co-incidence, and the possibility of population mixing, viruses, or chemicals as causes of the link. Radiation was a possible factor, and although the KiKK report stated that radiation doses were too low to be the cause, the researchers made no estimate of actual doses.

There are large uncertainties in estimates of radiations doses and risks near nuclear reactors, because doses are estimated on the basis of a set of different models. Each model has its own uncertainties, and combined they act to increase the distribution in the range of a dose estimate. Because of these uncertainties, radiation cannot be ruled out as a cause of childhood cancer near reactors.

The German researchers discounted the possibility of direct radiation shine, radiation from power lines, or emissions from cooling towers as causes of cancer increases, leaving reactor emissions and discharges as the only remaining possible cause. Dr Fairlie outlined a possible mechanism to explain the KiKK findings. Episodic spikes in releases from reactors – for example, when radioactive gases are vented when a reactor is opened for refuelling - could expose pregnant women in the vicinity to radionuclides, resulting in large radiation doses to embryos and foetusus. These babies are born pre-leukemic, and later develop full leukemia.

This view is supported by evidence from the German nuclear industry, which shows that nuclear reactor releases do occur in spikes, and in computer modelling of exposure to tritium doses from a Romanian nuclear reactor. Dr Farlie advised that regulators should insist that reactors are only vented at night, when most of the population is indoors, and when there is a strong wind in a seaward direction. The local population should also be advised of the potential risks.

A recent UK study by Bithell et al has investigated the increase in childhood leukemias near British nuclear power stations, although this study was conducted to a less robust standard than the KiKK study and also, without explanation, omitted the Calder Hall nuclear reactor. The Bithell study showed a 24% increase in the number of observed cancers over expected cancers. Because of the low sample size, the study was not able to demonstrate a statistically significant linkage between cancer and distance from nuclear installations at the 95% confidence interval, although the link was significant at an 85% confidence level. Despite this, Bithell et al concluded that there was “no evidence” of a link between childhood cancer and nuclear installations in the UK, in contrast to the findings of the KiKK study. These conclusions have been challenged in the academic press by Dr Fairlie and Alfred Korblein, who have pointed out that, unlike the case-controlled KiKK study, Bithell's team used a less robust desk study approach to their research.

Tritium, in particular, poses risks to health as it is can combine with hydrogen and oxygen to form a radioactive form of water. There is little information about tritium levels around nuclear power stations in the academic literature, but a Canadian government publication shows a logarithmic relationship between distance from nuclear power stations and concentrations of tritium both in the air and in food moisture.

Tritiated water is mobile and easily able to enter the human body. Although it is rapidly excreted it can also bind to organic complexes and can remain in close proximity to DNA structures within the cell. This makes it potentially more dangerous than more powerful radiation emitters, and it is likely that official models significantly underestimate the risks from tritium.

Dr Fairlie recommended that a precautionary approach should be taken with respect to radiation doses from nuclear reactors, and this should be taken into account in the current Justification process for the new nuclear power stations the government is planning to build. Further studies EU-wide should be undertaken to investigate the risks of low-level radiation, and local people should be advised of the potential risks and given health advice near nuclear reactor sites.

Click on the links below to download copies of Dr Fairlie's presentation and the new MEDACT briefing on tritium and health.