In the late1980s and early 1990s, a number of UK studies revealed increased incidences of childhood leukemias near the nuclear facilities at Windscale (now Sellafield), Burghfield and Dounreay. The official reaction to these increases was that the estimated radiation doses from intakes of nuclides released by these facilities were too low (by 2 to 3 orders of magnitude) to explain the increased leukemias. Various explanations were offered for the increases, including population mixing, however these increases are still occurring despite the existence of long-stabilised populations.
The UK Governments Committee on the Medical Aspects of Radiation in the Environment (COMARE) then concluded that the explanation for the increased leukemias remained unknown but was unlikely to be radiation. In 2004, the CERRIE Committee discussed the matter and its Report (www.cerrie.org) stated that there could be very large cumulative uncertainties in internal dose estimates because of uncertainties in the biokinetic and dosimetric models used which had to be multiplied together. From the examples discussed by the CERRIE Committee, net uncertainties in dose could be large enough to explain the increased leukemias in populations near the UK facilities.
Three recent epidemiological studies have, somewhat startlingly, rekindled the childhood leukemia debate. In June 2007, a study by Baker and Hoel (2007) at the Medical University of South Carolina lent new support to the idea that increased leukemias were linked to nuclear facilities. The authors carried out a sophisticated meta-analysis of 17 research papers covering 136 nuclear sites in the UK, Canada, France, US, Germany, Japan and Spain. They found that death rates for children up to the age of 9 were elevated by 5 to 24 per cent, depending on their proximity to nuclear facilities, and by 2 to 18 per cent in children and young people up to the age of 25. Incidence rates were increased by 14 to 21 per cent in 0 to 9 year-olds and 7 to 10 percent in 0 to 25 year-olds.
But it is two very recent German studies which have dramatically re-opened the matter. They provide much stronger evidence of an association between increased incidences of childhood leukemias and nuclear installations than previous studies. They are also significant because of their unequivocal establishment of an inverse distance- effect relationship and because of the involvement of the German Governments BfS the equivalent of the UKs HPA in the KiKK study.
The first German study was published in June 2007 by Hoffmann et al. The authors found 14 cases of leukemia between 1990 and 2005 in children living within 5 km of the Krümmel nuclear plant in Geesthacht and a neighbouring nuclear research facility in northern Germany. The 14 observed leukemia cases significantly exceeded the 0.45 predicted cases based on county and national incidence rates. The team concluded that the Geesthacht cluster was (then) the largest series of childhood leukemia cases among the various leukemia clusters near other European nuclear facilities, including Dounreay and Sellafield, UK and La Hague, France.
However the second German study is the most important of the three. This is the KiKK study published in two articles by Spix et al in January 2008 and by Kaatsch et al in February 2008. (KiKK = Epidemiologische Studie zu Kinderkrebs in der Umgebung von Kernkraftwerken = Childhood Cancer in the Vicinity of Nuclear Power Plants).
The study covered 16 (out of 20) large nuclear reactor locations in Germany between 1980 and 2003, and examined 1,592 under-fives with cancer with a control group of 4,735 children. The KiKK studys main findings were a 0.60 fold increase in solid cancers and a 1.17 fold increase in leukaemias among young children living near German nuclear reactors. These increases are very large compared with the increases near other nuclear facilities (see Baker and Hoel above).
But more importantly, and controvertially, the study found an inverse distance - effect relationship linking the cancers directly to the nuclear facilities. The study tested this relationship by examining whether other risk factors (confounders) could have had an appreciable effect on the result. This proved not to be the case: the proximity of residence to the nuclear power plant remained the most likely explanation.
The KiKK study had been commissioned in 2003 by the Bundesampt fur Strahlenshutz (the German Federal Office for Radiation Protection, the equivalent of the UKs HPA) following prolonged pressure by IPPNW Germany and other citizen groups. The publication of the KiKK study in December 2007 resulted in a public outcry and considerable public debate in Germany which continues to this day and which has been unreported in the UK.
The KiKK authors stated they were surprised by their results, but as a result of the furore, they issued a further report to allay public fears (BfS, 2007). The authors stated that study only found a small number of cases of cancer: 37 observed cases where 17 would have been expected statistically. This meant that less than one additional leukaemia case occurred per year. However the authors failed to explain that leukemia is a rare disease and that the cancers had occurred in a sparsely populated region. The authors said that the 20 additional cases were only found within a 5 km radius. However they did not consider that the reciprocal distance rule would add many more cases if applied to the whole region.
With a touch of déjà vu for UK readers, the KiKK authors then alleged that the raised levels of childhood cancer could not be explained by radioactive emissions from the nuclear power plants because the estimated radiation doses were too low. The authors, seemingly, were unable to countenance the possibility that their estimated doses could contain the large uncertainties discussed in the CERRIE Report www.cerrie.org.
What is the cause of the increased cancers?
In both studies, the authors explained that population mixing was unlikely to account for the leukemia incidence because the populations had remained stable over the years studied. Coincidence as an explanatory model for these raised incidences was held improbable by the External Expert Group commissioned by the German Governments Bundesampt fur Strahlenschutz to supervise the drafting, the execution and evaluation of the KiKK study. Instead, it is now officially accepted in Germany (Weiss, 2007) that children living near nuclear power plants develop cancer and leukaemia more frequently than those living further away.
If nuclide emissions have been correctly measured (as claimed by the nuclear operators and regulatory authorities), then current environmental transport models may be wrong, or current biokinetic models for determining radiation doses to local residents may be incorrect, or the biological effects of incorporated radionuclides may have been underestimated. Or, more likely, all three.
An interesting aspect is that many of the reactors in the KiKK study are boiling water reactors (BWRs) notable for their relatively high tritium emissions. Tritium is the radioactive isotope of hydrogen and its most common form is radioactive water. Recently, the UK Governments AGIR group published a report (AGIR, 2007) which examined a number of unusual aspects of tritium and discussed questions surrounding its biokinetic and dosimetric models. The report concluded that tritiums hazards (ie its dose coefficient) should be doubled.
These 3 new studies (Baker and Hoel, Hoffmann et al, KiKK) are important in radiation protection terms, as they provide good evidence of strong associations between increased cancers and closeness to nuclear facilities. They raise questions about the wisdom of the UK Governments recent decision to build more nuclear reactors in the UK.
For more information, please refer to www.ippnw.de www.bfs.de
AGIR (2007) Review of Risks from Tritium. Independent Advisory Group on Ionising Radiation. UK Health Protection Agency Radiation Protection Division. Harwell, Oxon. www.hpa.org.uk/radiation/publications/hpa_responses/hpa_response_rce_4_december_2007.htm
Baker PJ and Hoel D (2007) Meta-analysis of standardized incidence and mortality rates of childhood leukaemia in proximity to nuclear facilities. European Journal of Cancer Care. 16, pp 355-363. July 2007.
BfS (2007) Unanimous Statement by the Expert Group commissioned by the German Federal Office for Radiation Protection (BfS) on the KiKK Study (in German, no English version available) 5 Dec 2007. www.bfs.de/de/kerntechnik/papiere/Expertengremium.html
Hoffmann W, Terschueren C, and Richardson DB (2007) Childhood Leukemia in the Vicinity of the Geesthacht Nuclear Establishments near Hamburg, Germany. Environmental Health Perspectives. Vol 115, No 6, June 2007. www.ehponline.org/members/2007/9861/9861.pdf
Kaatsch P, Spix C, Schulze-Rath R, Schmiedel S, Blettner M (2008) Leukaemia in young children living in the vicinity of German nuclear power plants. Int J Cancer. 2008 Feb 15; 122(4) pp 721-6.
Spix C, Schmiedel S, Kaatsch P, Schulze-Rath R, Blettner M (2008) Case-control study on childhood cancer in the vicinity of nuclear power plants in Germany 1980 2003. Eur J Cancer. 2008 Jan; 44(2) pp 275-84.
Weiss W (2007) Background information on the KiKK Study, Federal Office for Radiation Protection. see www.bfs.de/en/kerntechnik/papiere/kikk.html
By Dr IAN FAIRLIE