Epidemiological studies of leukaemia in children and young adults around nuclear facilities: a critical review

Infectious triggers and novel therapeutic opportunities in childhood B cell leukaemia

B cell acute lymphoblastic leukaemia (B-ALL) is the most common form of childhood cancer. Although treatment has advanced remarkably in the past 50 years, it still fails in ~20% of patients. Recent studies revealed that more than 5% of healthy newborns carry preleukaemic clones that originate in utero, but only a small percentage of these carriers will progress to overt B-ALL. The drivers of progression are unclear, but B-ALL incidence seems to be increasing in parallel with the adoption of modern lifestyles. Emerging evidence shows that a major driver for the conversion from the preleukaemic state to the B-ALL state is exposure to immune stressors, such as infection. Here, we discuss our current understanding of the environmental triggers and genetic predispositions that may lead to B-ALL, highlighting lessons from epidemiology, the clinic and animal models, and identifying priority areas for future research.

The truth will out: a reflection on the life and times of Alice Stewart

CONCLUSIONS

Dr Alice Stewart's research was pioneering, fundamental and challenging, and is now widely accepted.

Ionising radiation and childhood leukaemia revisited

Increased incidences of childhood acute leukaemia were noted among survivors of the atomic bombings of Hiroshima and Nagasaki. In Western societies, Childhood Acute Lymphoblastic Leukaemia has a distinct epidemiology peaking at 3 years old. Exposure to ionising radiation is an established hazard but it is difficult to gauge the precise risk of less than 100 mSv. Since 1983 significant leukaemia incidences have been reported among families residing near nuclear installations. The target cells (naïve neonatal lymphocytes) get exposed to multiple xenobiotic challenges and undergo extraordinary proliferation and physiological somatic genetic change. Population movements and ionising radiation are considered taking account of updated understanding of radiation biology, cancer cytogenetics and immunological diversity. Double Strand Breaks in DNA arise through metabolic generation of Reactive Oxygen Species, and nearly always are repaired; but mis-repairs can be oncogenic. Recombinant Activating Gene enzymes in rapidly dividing perinatal pre-B lymphocytes being primed for antibody diversity are targeted to Signal Sequences in the Immunoglobulin genes. off target pseudo-sequences may allow RAG enzymes to create autosomal DSBs which, when mis-repaired, become translocated oncogenes. Immunogens acting by chance at crucial stages may facilitate this. In such circumstances, oncogenic DSBs from ionising radiation are less likely to be significant.

Childhood cancer research in oxford III: The work of CCRG on ionising radiation

BACKGROUND

High doses of ionising radiation are a known cause of childhood cancer and great public and professional interest attaches to possible links between childhood cancer and lower doses, particularly of man-made radiation. This paper describes work done by the Childhood Cancer Research Group (CCRG) on this topic METHODS: Most UK investigations have made use of the National Registry of Childhood Tumours and associated controls. Epidemiological investigations have included national incidence and mortality analyses, geographical investigations, record linkage and case-control studies. Dosimetric studies use biokinetic and dosimetric modelling.

RESULTS

This paper reviews the work of the CCRG on the association between exposure to ionising radiation and childhood cancer, 1975-2014.

CONCLUSION

The work of CCRG has been influential in developing understanding of the causes of 'clusters' of childhood cancer and the risks arising from exposure to ionising radiation both natural and man-made. Some clusters around nuclear installations have certainly been observed, but ionising radiation does not seem to be a plausible cause. The group's work has also been instrumental in discounting the hypothesis that paternal preconception irradiation was a cause of childhood cancers and has demonstrated an increased leukaemia risk for children exposed to higher levels of natural gamma-ray radiation.

The Krümmel (Germany) Childhood Leukaemia Cluster: a review and update

The debate surrounding possible adverse health effects from the civil use of nuclear power under normal operating conditions has been on-going since its introduction. It was particularly intensified by the detection of three leukaemia clusters near nuclear installations, i.e. near the reprocessing plants in Sellafield and Dounreay, UK, and near the Krümmel nuclear power plant, Germany, the last of which commenced between 1990 and 1991 and was first described in 1992; it continued until 2003, and an elevated risk up to 2005 has been reported in the literature. A number of expert commissions and working groups were set up by the governments of the German federal states of Lower Saxony and Schleswig-Holstein to investigate the possible causes of the cluster. An overview of the many risk factors that were investigated as a possible explanation of the Krümmel cluster is given here, focussing on radiation, but also including other risk factors. Further, results from related epidemiological and cytogenetic studies are described. In summary, the cause of the occurrence of the Krümmel cluster has to be considered as unknown. Further research on the causes of childhood leukaemia is needed, focussing on epigenetics and on gene-environment interaction. An update of the leukaemia incidence around the Krümmel site shows that the incidence rates are now comparable to the average rate in Germany.

Paternal programming of offspring cardiometabolic diseases in later life

Early - intrauterine - environmental factors are linked to the development of cardiovascular disease in later life. Traditionally, these factors are considered to be maternal factors such as maternal under and overnutrition, exposure to toxins, lack of micronutrients, and stress during pregnancy. However, in the recent years, it became obvious that also paternal environmental factors before conception and during sperm development determine the health of the offspring in later life. We will first describe clinical observational studies providing evidence for paternal programming of adulthood diseases in progeny. Next, we describe key animal studies proving this relationship, followed by a detailed analysis of our current understanding of the underlying molecular mechanisms of paternal programming. Alterations of noncoding sperm micro-RNAs, histone acetylation, and targeted as well as global DNA methylation seem to be in particular involved in paternal programming of offspring's diseases in later life.

Radiation Safety in Nuclear Medicine Procedures

Since the nuclear disaster at the Fukushima Daiichi Nuclear Power Plant in 2011, radiation safety has become an important issue in nuclear medicine. Many structured guidelines or recommendations of various academic societies or international campaigns demonstrate important issues of radiation safety in nuclear medicine procedures. There are ongoing efforts to fulfill the basic principles of radiation protection in daily nuclear medicine practice. This article reviews important principles of radiation protection in nuclear medicine procedures. Useful references, important issues, future perspectives of the optimization of nuclear medicine procedures, and diagnostic reference level are also discussed.

Updated investigations of cancer excesses in individuals born or resident in the vicinity of Sellafield and Dounreay

BACKGROUND

Earlier studies have shown raised risks of leukaemia and non-Hodgkin lymphoma in children, teenagers and young adults resident either at birth or diagnosis in Seascale. Some increases in cancer risk in these age groups have also been noted among those living around Dounreay. We aimed to update previous analyses relating to areas close to these nuclear installations by considering data from an additional 16 years of follow-up.

METHODS

Cross-sectional analyses compared cancer incidence rates for 1963-2006 among those aged 0-24 years at diagnosis living in geographically specified areas around either Sellafield or Dounreay with general population rates. Cancer incidence for the period 1971-2006 among the cohort of Cumbrian births between 1950 and 2006 was compared to national incidence for 1971-2006 using person-years analysis. Cancer among those born in the postcode sector closest to Dounreay was compared with that among those born in the three adjoining postcode sectors. Analyses considered both cancer overall and ICD-O-3 defined diagnostic subgroups including leukaemia, central nervous system tumours and other malignancies.

RESULTS

Apart from previously reported raised risks, no new significantly increased risks for cancer overall or any diagnostic subgroup were found among children or teenagers and young adults living around either nuclear installation. Individuals born close to the installations from 1950 to 2006 were not shown to be at any increased risk of cancer during the period 1971 to date.

CONCLUSIONS

Analysis of recent data suggests that children, teenagers and young adults currently living close to Sellafield and Dounreay are not at an increased risk of developing cancer. Equally, there is no evidence of any increased cancer risk later in life among those resident in these areas at birth.

Epidemiological evidence of childhood leukaemia around nuclear power plants

A few reports of increased numbers of leukaemia cases (clusters) in children living in the vicinity of nuclear power plants (NPP) and other nuclear installations have triggered a heated debate over the possible causes of the disease. In this review the most important cases of childhood leukaemia clusters around NPPs are described and analyzed with special emphasis on the relationship between the environmental exposure to ionizing radiation and the risk of leukaemia. Since, as indicated, a lifetime residency in the proximity of an NPP does not pose any specific health risk to people and the emitted ionizing radiation is too small to cause cancer, a number of hypotheses have been proposed to explain the childhood leukaemia clusters. The most likely explanation for the clusters is 'population mixing', i.e., the influx of outside workers to rural regions where nuclear installations are being set up and where local people are not immune to pathogens brought along with the incomers.

Childhood leukaemia risks: from unexplained findings near nuclear installations to recommendations for future research

Recent findings related to childhood leukaemia incidence near nuclear installations have raised questions which can be answered neither by current knowledge on radiation risk nor by other established risk factors. In 2012, a workshop was organised on this topic with two objectives: (a) review of results and discussion of methodological limitations of studies near nuclear installations; (b) identification of directions for future research into the causes and pathogenesis of childhood leukaemia. The workshop gathered 42 participants from different disciplines, extending widely outside of the radiation protection field. Regarding the proximity of nuclear installations, the need for continuous surveillance of childhood leukaemia incidence was highlighted, including a better characterisation of the local population. The creation of collaborative working groups was recommended for consistency in methodologies and the possibility of combining data for future analyses. Regarding the causes of childhood leukaemia, major fields of research were discussed (environmental risk factors, genetics, infections, immunity, stem cells, experimental research). The need for multidisciplinary collaboration in developing research activities was underlined, including the prevalence of potential predisposition markers and investigating further the infectious aetiology hypothesis. Animal studies and genetic/epigenetic approaches appear of great interest. Routes for future research were pointed out.

A hypothesis to explain childhood cancers near nuclear power plants

Over 60 epidemiological studies world-wide have examined cancer incidences in children near nuclear power plants (NPPs): most of them indicate leukemia increases. These include the 2008 KiKK study commissioned by the German Government which found relative risks (RR) of 1.6 in total cancers and 2.2 in leukemias among infants living within 5 km of all German NPPs. The KiKK study has retriggered the debate as to the cause(s) of these increased cancers. A suggested hypothesis is that the increased cancers arise from radiation exposures to pregnant women near NPPs. However any theory has to account for the >10,000 fold discrepancy between official dose estimates from NPP emissions and observed increased risks. An explanation may be that doses from spikes in NPP radionuclide emissions are significantly larger than those estimated by official models which are diluted through the use of annual averages. In addition, risks to embryos/fetuses are greater than those to adults and haematopoietic tissues appear more radiosensitive in embryos/fetuses than in newborn babies. The product of possible increased doses and possible increased risks per dose may provide an explanation.

Thyroid cancer incidence in the vicinity of nuclear sites in Belgium, 2000-2008

BACKGROUND

Public health concern about nuclear activities have existed since the 1980s. Most studies on this subject investigated childhood leukemia. Thyroid cancer may be another health outcome of interest, because some nuclear installations are a potential source of radioactive iodine isotopes in the environment and because thyroid cancer is known to occur after exposure to these isotopes.

METHODS

This study describes an ecological study investigating whether there is excessive thyroid cancer incidence among residents living in the vicinity of nuclear sites. Single-site analyses using indirect standardization (standardized incidence ratios [SIRs]) and Poisson regression modeling (rate ratios [RRs]) were conducted. The proximity area is typically defined as a circular zone with a radius of 20 km centered on the site. However, the choice of the size of this area is somewhat arbitrary. Therefore, a sensitivity analysis was carried out to investigate whether the results vary with radii of increasing proximity.

RESULTS

No increased thyroid cancer incidence was found within the 20 km proximity area around the nuclear power plants of Doel (SIR=0.74 [95% confidence interval (CI)=0.64; 0.84] and RR=0.72 [95% CI=0.63; 0.83]) and Tihange (SIR=0.86 [95% CI=0.70; 1.01] and RR=0.85 [95% CI=0.70; 1.02]). For the sites of Mol-Dessel and Fleurus, where a combination of nuclear research and industrial activities are located, the incidences of thyroid cancer within the 20 km proximity area were higher than expected (Mol-Dessel: SIR=1.19 [95% CI=1.01; 1.36] and RR=1.19 [95% CI=1.02; 1.38]; Fleurus: SIR=1.15 [95% CI=1.02; 1.28] and RR=1.17 [95% CI=1.04; 1.33]). For Chooz, a French nuclear power plant close to the Belgian border, the results were unstable as a result of the small population denominator. For all Belgian nuclear sites, the results were generally insensitive to the choice of the proximity area.

CONCLUSIONS

No evidence for excessive thyroid cancer incidence around the Belgian nuclear power plants was found. On the other hand, an increased incidence of thyroid cancer was observed around the sites with other nuclear activities. Further research is recommended to verify whether the observed increases could be related to the site-specific nuclear activities.

A paternal environmental legacy: evidence for epigenetic inheritance through the male germ line

Literature on maternal exposures and the risk of epigenetic changes or diseases in the offspring is growing. Paternal contributions are often not considered. However, some animal and epidemiologic studies on various contaminants, nutrition, and lifestyle-related conditions suggest a paternal influence on the offspring's future health. The phenotypic outcomes may have been attributed to DNA damage or mutations, but increasing evidence shows that the inheritance of environmentally induced functional changes of the genome, and related disorders, are (also) driven by epigenetic components. In this essay we suggest the existence of epigenetic windows of susceptibility to environmental insults during sperm development. Changes in DNA methylation, histone modification, and non-coding RNAs are viable mechanistic candidates for a non-genetic transfer of paternal environmental information, from maturing germ cell to zygote. Inclusion of paternal factors in future research will ultimately improve the understanding of transgenerational epigenetic plasticity and health-related effects in future generations.

Independent analysis of the radiation risk for leukaemia in children and adults with mortality data (1950-2003) of Japanese A-bomb survivors

A recent analysis of leukaemia mortality in Japanese A-bomb survivors has applied descriptive models, collected together from previous studies, to derive a joint excess relative risk estimate (ERR) by multi-model inference (MMI) (Walsh and Kaiser in Radiat Environ Biophys 50:21-35, 2011). The models use a linear-quadratic dose response with differing dose effect modifiers. In the present study, a set of more than 40 models has been submitted to a rigorous statistical selection procedure which fosters the parsimonious deployment of model parameters based on pairwise likelihood ratio tests. Nested models were consequently excluded from risk assessment. The set comprises models of the excess absolute risk (EAR) and two types of non-standard ERR models with sigmoidal responses or two line spline functions with a changing slope at a break point. Due to clearly higher values of the Akaike Information Criterion, none of the EAR models has been selected, but two non-standard ERR models qualified for MMI. The preferred ERR model applies a purely quadratic dose response which is slightly damped by an exponential factor at high doses and modified by a power function for attained age. Compared to the previous analysis, the present study reports similar point estimates and confidence intervals (CI) of the ERR from MMI for doses between 0.5 and 2.5 Sv. However, at lower doses, the point estimates are markedly reduced by factors between two and five, although the reduction was not statistically significant. The 2.5 % percentiles of the ERR from the preferred quadratic-exponential model did not fall below zero risk in exposure scenarios for children, adolescents and adults at very low doses down to 10 mSv. Yet, MMI produced risk estimates with a positive 2.5 % percentile only above doses of some 300 mSv. Compared to CI from a single model of choice, CI from MMI are broadened in cohort strata with low statistical power by a combination of risk extrapolations from several models. Reverting to MMI can relieve the dilemma of needing to choose between models with largely different consequences for risk assessment in public health.

An ecological study of cancer incidence in Port Hope, Ontario from 1992 to 2007

A plant processing radium and uranium ores has been operating in the town of Port Hope since 1932. Given the nuclear industry located in the community and ongoing public health concerns, cancer incidence rates in Port Hope were studied for a recent 16 year period (1992-2007) for continued periodic cancer incidence surveillance of the community. The cancer incidence in the local community for all cancers combined was similar to the Ontario population, health regions with similar socio-economic characteristics in Ontario and in Canada, and the Canadian population. No statistically significant differences in childhood cancer, leukaemia or other radiosensitive cancer incidence were observed, with the exception of statistically significant elevated lung cancer incidence among women. However, the statistical significance was reduced or disappeared when the comparison was made to populations with similar socio-economic characteristics. These findings are consistent with previous ecological, case-control and cohort studies conducted in Port Hope, environmental assessments, and epidemiological studies conducted elsewhere on populations living around similar facilities or exposed to similar environmental contaminants. Although the current study covered an extended period of time, the power to detect risk at the sub-regional level of analysis was limited since the Port Hope population is small (16,500). The study nevertheless indicated that large differences in cancer incidence are not occurring in Port Hope compared to other similar communities and the general population.

The risk of childhood leukaemia following exposure to ionising radiation--a review

Since the early years of follow-up of the Japanese atomic-bomb survivors, it has been apparent that childhood leukaemia has a particular sensitivity to induction by ionising radiation, the excess relative risk (ERR) being expressed as a temporal wave with time since exposure. This pattern has been generally confirmed by studies of children treated with radiotherapy. Case-control studies of childhood leukaemia and antenatal exposure to diagnostic x-rays, a recent large cohort study of leukaemia following CT examinations of young people, and a recent large case-control study of natural background γ-radiation and childhood leukaemia have found evidence of raised risks following low-level exposure. These findings indicate that an ERR/Sv for childhood leukaemia of ~50, which may be derived from risk models based upon the Japanese atomic-bomb survivors, is broadly applicable to low dose or low dose-rate exposure circumstances.

Geographical variation in dementia: systematic review with meta-analysis

BACKGROUND

Geographical variation in dementia prevalence and incidence may indicate important socio-environmental contributions to dementia aetiology. However, previous comparisons have been hampered by combining studies with different methodologies. This review systematically collates and synthesizes studies examining geographical variation in the prevalence and incidence of dementia based on comparisons of studies using identical methodologies.

METHODS

Papers were identified by a comprehensive electronic search of relevant databases, scrutinising the reference sections of identified publications, contacting experts in the field and re-examining papers already known to us. Identified articles were independently reviewed against inclusion/exclusion criteria and considered according to geographical scale. Rural/urban comparisons were meta-analysed.

RESULTS

Twelve thousand five hundred and eighty records were reviewed and 51 articles were included. Dementia prevalence and incidence varies at a number of scales from the national down to small areas, including some evidence of an effect of rural living [prevalence odds ratio (OR) = 1.11, 90% confidence interval (CI) 0.79-1.57; incidence OR = 1.20, 90% CI 0.84-1.71]. However, this association of rurality was stronger for Alzheimer disease, particularly when early life rural living was captured (prevalence OR = 2.22, 90% CI 1.19-4.16; incidence OR = 1.64, 90% CI 1.08-2.50).

CONCLUSIONS

There is evidence of geographical variation in rates of dementia in affluent countries at a variety of geographical scales. Rural living is associated with an increased risk of Alzheimer disease, and there is a suggestion that early life rural living further increases this risk. However, the fact that few studies have been conducted in resource-poor countries limits conclusions.

Childhood cancer and nuclear power plants in Switzerland: a census-based cohort study

BACKGROUND

Previous studies on childhood cancer and nuclear power plants (NPPs) produced conflicting results. We used a cohort approach to examine whether residence near NPPs was associated with leukaemia or any childhood cancer in Switzerland.

METHODS

We computed person-years at risk for children aged 0-15 years born in Switzerland from 1985 to 2009, based on the Swiss censuses 1990 and 2000 and identified cancer cases from the Swiss Childhood Cancer Registry. We geo-coded place of residence at birth and calculated incidence rate ratios (IRRs) with 95% confidence intervals (CIs) comparing the risk of cancer in children born <5 km, 5-10 km and 10-15 km from the nearest NPP with children born >15 km away, using Poisson regression models.

RESULTS

We included 2925 children diagnosed with cancer during 21 117 524 person-years of follow-up; 953 (32.6%) had leukaemia. Eight and 12 children diagnosed with leukaemia at ages 0-4 and 0-15 years, and 18 and 31 children diagnosed with any cancer were born <5 km from a NPP. Compared with children born >15 km away, the IRRs (95% CI) for leukaemia in 0-4 and 0-15 year olds were 1.20 (0.60-2.41) and 1.05 (0.60-1.86), respectively. For any cancer, corresponding IRRs were 0.97 (0.61-1.54) and 0.89 (0.63-1.27). There was no evidence of a dose-response relationship with distance (P > 0.30). Results were similar for residence at diagnosis and at birth, and when adjusted for potential confounders. Results from sensitivity analyses were consistent with main results.

CONCLUSIONS

This nationwide cohort study found little evidence of an association between residence near NPPs and the risk of leukaemia or any childhood cancer.

Cancer risks near nuclear facilities: the importance of research design and explicit study hypotheses

BACKGROUND

In April 2010, the U.S. Nuclear Regulatory Commission asked the National Academy of Sciences to update a 1990 study of cancer risks near nuclear facilities. Prior research on this topic has suffered from problems in hypothesis formulation and research design.

OBJECTIVES

We review epidemiologic principles used in studies of generic exposure-response associations and in studies of specific sources of exposure. We then describe logical problems with assumptions, formation of testable hypotheses, and interpretation of evidence in previous research on cancer risks near nuclear facilities.

DISCUSSION

Advancement of knowledge about cancer risks near nuclear facilities depends on testing specific hypotheses grounded in physical and biological mechanisms of exposure and susceptibility while considering sample size and ability to adequately quantify exposure, ascertain cancer cases, and evaluate plausible confounders.

CONCLUSIONS

Next steps in advancing knowledge about cancer risks near nuclear facilities require studies of childhood cancer incidence, focus on in utero and early childhood exposures, use of specific geographic information, and consideration of pathways for transport and uptake of radionuclides. Studies of cancer mortality among adults, cancers with long latencies, large geographic zones, and populations that reside at large distances from nuclear facilities are better suited for public relations than for scientific purposes.

Multi-model inference of adult and childhood leukaemia excess relative risks based on the Japanese A-bomb survivors mortality data (1950-2000)

Some relatively new issues that augment the usual practice of ignoring model uncertainty, when making inference about parameters of a specific model, are brought to the attention of the radiation protection community here. Nine recently published leukaemia risk models, developed with the Japanese A-bomb epidemiological mortality data, have been included in a model-averaging procedure so that the main conclusions do not depend on just one type of model or statistical test. The models have been centred here at various adult and young ages at exposure, for some short times since exposure, in order to obtain specially computed childhood Excess Relative Risks (ERR) with uncertainties that account for correlations in the fitted parameters associated with the ERR dose-response. The model-averaged ERR at 1 Sv was not found to be statistically significant for attained ages of 7 and 12 years but was statistically significant for attained ages of 17, 22 and 55 years. Consequently, such risks when applied to other situations, such as children in the vicinity of nuclear installations or in estimates of the proportion of childhood leukaemia incidence attributable to background radiation (i.e. low doses for young ages and short times since exposure), are only of very limited value, with uncertainty ranges that include zero risk. For example, assuming a total radiation dose to a 5-year-old child of 10 mSv and applying the model-averaged risk at 10 mSv for a 7-year-old exposed at 2 years of age would result in an ERR=0.33, 95% CI: -0.51 to 1.22. One model (United Nations scientific committee on the effects of atomic radiation report. Volume 1. Annex A: epidemiological studies of radiation and cancer, United Nations, New York, 2006) weighted model-averaged risks of leukaemia most strongly by half of the total unity weighting and is recommended for application in future leukaemia risk assessments that continue to ignore model uncertainty. However, on the basis of the analysis presented here, it is generally recommended to take model uncertainty into account in future risk analyses.

Childhood leukaemia, nuclear sites, and population mixing

The excess of childhood leukaemia (CL) in Seascale, near the Sellafield nuclear reprocessing site in rural NW England, suggested that an epidemic of an underlying infection, to which CL is a rare response, is promoted by marked population mixing (PM) in rural areas, in which the prevalence of susceptibles is higher than average. This hypothesis has been confirmed by 12 studies in non-radiation situations. Of the five established CL excesses near nuclear sites, four are associated with significant PM; in the fifth, the Krummel power station in Germany, the subject has not been thoroughly investigated.

Temporal trends in childhood leukaemia incidence following exposure to radioactive fallout from atmospheric nuclear weapons testing

Notably raised rates of childhood leukaemia incidence have been found near some nuclear installations, in particular Sellafield and Dounreay in the United Kingdom, but risk assessments have concluded that the radiation doses estimated to have been received by children or in utero as a result of operations at these installations are much too small to account for the reported increases in incidence. This has led to speculation that the risk of childhood leukaemia arising from internal exposure to radiation following the intake of radioactive material released from nuclear facilities has been substantially underestimated. The radionuclides discharged from many nuclear installations are similar to those released into the global environment by atmospheric nuclear weapons testing, which was at its height in the late-1950s and early-1960s. Measurements of anthropogenic radionuclides in members of the general public resident in the vicinity of Sellafield and Dounreay have found levels that do not differ greatly from those in persons living remote from nuclear installations that are due to ubiquitous exposure to the radioactive debris of nuclear weapons testing. Therefore, if the leukaemia risk to children resulting from deposition within the body of radioactive material discharged from nuclear facilities has been grossly underestimated, then a pronounced excess of childhood leukaemia would have been expected as a consequence of the short period of intense atmospheric weapons testing. We have examined childhood leukaemia incidence in 11 large-scale cancer registries in three continents for which data were available at least as early as 1962. We found no evidence of a wave of excess cases corresponding to the peak of radioactive fallout from atmospheric weapons testing. The absence of a discernible increase in the incidence of childhood leukaemia following the period of maximum exposure to the radioactive debris of this testing weighs heavily against the suggestion that conventional methods are seriously in error when assessing the risk of childhood leukaemia from exposure to man-made radionuclides released from nuclear installations.

Childhood cancer near German nuclear power stations

In 2008, the Kinderkrebs in der Umgebung von Kernkraftwerken (KiKK) study in Germany reported a 60% increase in solid cancers and a 120% increase in leukemias among children living within 5 km of all German nuclear power stations. The study has triggered debates as to the cause(s) of these increased cancers. This article reports on the findings of the KiKK study; discusses past and more recent epidemiological studies of leukemias near nuclear installations around the world, and outlines a possible biological mechanism to explain the increased cancers. This suggests that the observed high rates of infant leukemias may be a teratogenic effect from radionuclides incorporated by pregnant women living near nuclear reactors. Doses and risks from environmental emissions to embryos and fetuses may be larger than suspected. Hematopoietic tissues appear to be considerably more radiosensitive in embryos/fetuses than in newborn babies. Recommendations for advice to local residents and for further research are made.

Cancer incidence in the vicinity of Finnish nuclear power plants: an emphasis on childhood leukemia

The objective of this paper was to study cancer incidence, especially leukemia in children (<15 years), in the vicinity of Finnish nuclear power plants (NPPs). We used three different approaches: ecological analysis at municipality level, residential cohorts defined from census data, and case–control analysis with individual residential histories. The standardized incidence ratio of childhood leukemia for the seven municipalities in the vicinity of NPPs was 1.0 (95% CI 0.6, 1.6) compared to the rest of Finland. The two cohorts defined by censuses of 1980 and 1990 gave rate ratios of 1.0 (95% CI 0.3, 2.6) and 0.9 (95% CI 0.2, 2.7), respectively, for childhood leukemia in the population residing within 15 km from the NPPs compared to the 15–50 km zone. The case–control analysis with 16 cases of childhood leukemia and 64 matched population-based controls gave an odds ratio for average distance between residence and NPP in the closest 5–9.9 km zone of 0.7 (95% CI 0.1, 10.4) compared to ≥30 km zone. Our results do not indicate an increase in childhood leukemia and other cancers in the vicinity of Finnish NPPs though the small sample size limits the strength of conclusions. The conclusion was the same for adults.

Childhood leukemia and cancers near German nuclear reactors: significance, context, and ramifications of recent studies

A government-sponsored study of childhood cancer in the proximity of German nuclear power plants (German acronym KiKK) found that children < 5 years living < 5 km from plant exhaust stacks had twice the risk for contracting leukemia as those residing > 5 km. The researchers concluded that since "this result was not to be expected under current radiation-epidemiological knowledge" and confounders could not be identified, the observed association of leukemia incidence with residential proximity to nuclear plants "remains unexplained." This unjustified conclusion illustrates the dissonance between evidence and assumptions. There exist serious flaws and gaps in the knowledge on which accepted models for population exposure and radiation risk are based. Studies with results contradictory to those of KiKK lack statistical power to invalidate its findings. The KiKK study's ramifications add to the urgency for a public policy debate regarding the health impact of nuclear power generation.

Commentary: childhood cancer near nuclear power stations

In 2008, the KiKK study in Germany reported a 1.6-fold increase in solid cancers and a 2.2-fold increase in leukemias among children living within 5 km of all German nuclear power stations. The study has triggered debates as to the cause(s) of these increased cancers. This article reports on the findings of the KiKK study; discusses past and more recent epidemiological studies of leukemias near nuclear installations around the world, and outlines a possible biological mechanism to explain the increased cancers. This suggests that the observed high rates of infant leukemias may be a teratogenic effect from incorporated radionuclides. Doses from environmental emissions from nuclear reactors to embryos and fetuses in pregnant women near nuclear power stations may be larger than suspected. Hematopoietic tissues appear to be considerably more radiosensitive in embryos/fetuses than in newborn babies. Recommendations for advice to local residents and for further research are made.