A cluster of childhood leukemia near a nuclear reactor in northern Germany

A Short Latency between Radiation Exposure from Nuclear Plants and Cancer in Young Children

Previous reports document a short latency of cancer onset in young children exposed to low doses of radioactivity. The standard mortality ratio (SMR) for cancer in children dying before age ten rose in the period 6–10 years after the Three Mile Island and Chernobyl accidents in populations most exposed to fallout. SMRs near most nuclear power plants were elevated 6–10 years after startup, particularly for leukemia. Cancer incidence in children under age ten living near New York and New Jersey nuclear plants increased 4–5 years after increases in average strontium-90 in baby teeth, and declined 4–5 years after Sr-90 averages dropped. The assumption that Sr-90 and childhood cancer are correlated is best supported for a supralinear dose-response, meaning the greatest per-dose risks are at the lowest doses. Findings document that the very young are especially susceptible to adverse effects of radiation exposure, even at relatively low doses.

Thyroid cancer incidence around the Belgian nuclear sites: surrogate exposure modelling

BACKGROUND

In a recent ecological study among residents living around Belgian nuclear sites (the NUCABEL study), significant increased incidences of thyroid cancer were observed around the two nuclear facilities with industrial and research activities (Mol-Dessel and Fleurus), prompting further research.

METHODS

The data from the NUCABEL study were reanalysed to test the hypothesis of a gradient in cancer incidence with increasing levels of exposure from these sites using three measures of surrogate exposure, being (i) residential proximity, (ii) prevailing wind directions and (iii) simulated dispersion of radioactive discharges. Single-site focussed hypothesis tests were complemented with Generalized Additive Models to estimate the exposure-response relationships.

RESULTS

For Mol-Dessel, the results of the focussed hypothesis tests were far from significant. For Fleurus, the p-values were much closer to significance with p=0.05 for Bithell's Linear Risk Score using radioactive discharge estimates as surrogate.

CONCLUSIONS

The re-analyses refute an association with the nuclear facilities for the site of Mol-Dessel. For the site of Fleurus, one of Europe's major production sites of radio-iodines, the results were less conclusive and further research suggests itself.

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.

The 'Kinderkrebs in der Umgebung von Kernkraftwerken' study: results put into perspective

A German case-control study on leukaemia in children below 5 y of age near nuclear installations showed a trend of increasing risk with decreasing distance of place of residence from the sites. The radiation exposure from the sites is considered as being too low by a factor of at least 1000 to explain the observed effect, but little is known about radiation effects from pre- or postnatal exposures on the leukaemia risk for ages up to 4 y. Within the study, it was shown that the observed trend in risk decreases over time. That could be indicative of some agent being involved for which the prevalence is reduced over time. Previous ecological studies showed increased risks among the youngest age groups in the closest vicinity of the sites, but no elevated risks for children of all ages (0-14). This could implicate a shift towards an earlier onset of the disease.

Population-based research on occupational and environmental factors for leukemia and non-Hodgkin's lymphoma: the Northern Germany Leukemia and Lymphoma Study (NLL)

BACKGROUND

The Northern Germany Leukemia and Lymphoma Study (NLL) is a population-based study designed to provide a quantitative basis for investigations into occupational and environmental risk factors for leukemia and lymphoma.

METHODS

All incident cases of leukemia and lymphoma diagnosed between 1/1/1986 and 12/31/1998 in six counties in Northern Germany were actively ascertained. Controls were selected from population registries. Use of pesticides, sources of food supply, time spent at home and work, medical and family history were assessed via face-to-face interview. This self-reported information was used in conjunction with direct environmental measurements of pesticides in household dust and electromagnetic fields (EMFs). In addition, geographical information system (GIS) data were used to derive estimates of environmental exposure to pesticides, EMFs associated with transmission lines, and ionizing radiation from routine nuclear power reactor operations. Occupational exposure assessment was based on lifetime work history. For each job, information on branch of industry, company, job description, and duration of employment were ascertained.

RESULTS

Fourteen hundred thirty cases and 3041 controls were recruited. Lifetime residential and workplace histories totaled 49,628 addresses. Occupational exposure to pesticides was reported by 15% of the male participants (women: 16%). Four percent of the men (women: 8%) were occupationally exposed to ionizing radiation for >or=1 year over their lifetime. Sixty four percent of the participants had lived in the vicinity (20 km) of a nuclear power plant in operation.

CONCLUSIONS

The NLL illustrates the successful application of innovative methods to simultaneously assess occupational and environmental risk factors for leukemia and lymphoma including radiological hazards, pesticides, and EMFs.

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

The existence of an increased risk of childhood leukaemia near nuclear installations is a recurrent issue. A review of the related epidemiological literature is presented here. Results for 198 nuclear sites throughout 10 countries were included in the review. In addition to local studies, 25 multi-site studies have been published for eight countries. A large variability was noticed in the quality of the data as well as in the definition of the study population and in the methods of analysis. Many studies present important limits that make the results difficult to interpret. The review confirms that some clusters of childhood leukaemia cases exist locally. However, results based on multi-site studies around nuclear installations do not indicate an increased risk globally. Many studies were launched to investigate possible origins of the observed clusters around specific sites, but up to now, none of the proposed hypotheses have explained them.

Childhood leukemia in the vicinity of the Geesthacht nuclear establishments near Hamburg, Germany

BACKGROUND

During 1990-1991 a childhood leukemia cluster was observed in the sparsely populated region surrounding two nuclear establishments southeast of Hamburg, Germany. Since then, several new cases have been reported. Recently a possible accidental release of radionuclides in 1986 was hypothesized.

OBJECTIVE

The objective of this study was to analyze the childhood leukemia incidence in this area since 1990.

METHODS

All incident cases (< 15 years of age) were ascertained during 1990-2005 within a 5-km radius of the Krümmel nuclear power plant. We derived standardized incidence ratios (SIRs) using county and national leukemia incidence rates as referents. We stratified analyses by calendar period and attained age, and by subdividing the study region into areas north versus south of the Elbe river.

RESULTS

Fourteen cases were ascertained in the study area, whereas 4.0 were expected based on national referent rates [1990-2005: SIR = 3.5; 95% confidence interval (CI), 1.9-5.9]. The excess was not confined to the early 1990s; for the more recent time period 1999-2005, the SIR is still elevated (SIR = 2.7; 95% CI, 0.9-6.2). SIRs of greatest magnitude were observed for children 0-4 years of age (SIR = 4.9; 95% CI, 2.4-9.0) and for residents south of the Elbe (SIR = 7.5; 95% CI, 2.8-16.4).

CONCLUSIONS

The incidence in this region is significantly higher than the childhood leukemia incidence for Germany as a whole. To date, no unique hazards have been identified in this population. The fact that the elevated rates have persisted in this community for > 15 years warrants further investigation.

The Elbmarsch leukemia cluster: are there conceptual limitations in controlling immission from nuclear establishments in Germany?

The childhood leukemia cluster in the proximity of the German nuclear establishments of Geesthacht is unique in its spatial and temporal concentration. After a steep increase in cases in 1990, the cluster continues to show a significant increase up to the present. Early investigations of blood samples from a casual sample of local residents showed an increase in dicentric chromosomes in lymphocytes, indicating exposure exceeding dose limits. Analyses of the immission data revealed several unexpected deliveries of fission and activation products in the environment but provided no explanation of the source. Because of the observed overdispersion of dicentric chromosomes in cells, the idea of a contribution by densely ionizing emitters was compelling. The routine programs, however, do not include alpha emitters. These were measured in specific studies that proved contamination by transuranic nuclides. As shown in the present investigation, routine environmental surveillance programs support the occurrence of an accidental event near Geesthacht in September 1986. Until now, neither the cause nor the complete scenario of the activity release could be established. The ongoing discussion highlights limitations in the immission-control concept, which is predominantly based on gamma-radiation monitoring.

Transuranic isotopes and 90Sr in attic dust in the vicinity of two nuclear establishments in northern Germany

Attic dust was chosen as the test medium in order to search for traces of man-made bone seeking alpha and beta emitters. The samples were taken from 5 houses in the community of Elbmarsch situated at the river Elbe, adjacent to the Krümmel nuclear power plant and the nuclear research center of Geesthacht. Five houses in other regions of northern Germany were taken as a control. 238Pu, (239,240)Pu, 241Am, and 244Cm were measured by alpha spectrometry after chemical separation. Additionally, 241Pu was measured by liquid scintillation spectrometry, and the fission product 90Sr was measured in a separate investigation. All nuclides except 244Cm showed activities above the detection limit in the Elbmarsch samples and an elevated mean concentration compared to the control. It can be concluded from the activity ratio 241Am/(239,240)Pu that the Elbmarsch contamination cannot be accounted for by the background levels of transuranic nuclides resulting from weapons fallout. The derived release of alpha emitters is assumed to have contributed to the induction of a leukemia cluster in children, which was observed in Elbmarsch between 1990 and 1996.

Elevated childhood cancer incidence proximate to U.S. nuclear power plants

Numerous reports document elevated cancer rates among children living near nuclear facilities in various nations. Little research has examined U.S. rates near the nation's 103 operating reactors. This study determined that cancer incidence for children < 10 yr of age who live within 30 mi (48 km) of each of 14 nuclear plants in the eastern United States (49 counties with a population > 16.8 million) exceeds the national average. The excess 12.4% risk suggests that 1 in 9 cancers among children who reside near nuclear reactors is linked to radioactive emissions. If cancer incidence in 5 western states is used as a baseline, the ratio is closer to 1 in 5. Incidence is particularly elevated for leukemia. Childhood cancer mortality exceeds the national average in 7 of the 14 study areas.

Clusters and clustering of childhood cancer: a review

Methodological considerations in the study of clusters and clustering of childhood cancer are reviewed briefly. A selection of 11 studies of individual clusters of childhood leukaemia which are either particularly notable or recent and have been reported in peer review journals is then considered. Focus is placed on sources of alerts, descriptive studies, field-work studies, conclusions and communication management. Some of these studies are probably essential but they are unlikely to yield firm conclusions; studies of large data sets are recommended. No causal factor has been identified which can explain a single cluster of childhood leukaemia.

Leukaemia in the vicinity of two tritium-releasing nuclear facilities: a comparison of the Kruemmel Site, Germany, and the Savannah River Site, South Carolina, USA

In 1991, an increased rate of childhood leukaemia was reported from the small northern German community of Elbmarsch, which is located on the banks of the River Elbe opposite the Kruemmel nuclear power plant. Owing to the fact that the increase occurred six years after the start-up of the plant, radioactive discharges were suspected as being implicated in the development of the cases. Previous investigations have failed to identify any exposure which might be associated with the cluster. Nonetheless, concern regarding the increased tritium burden in the environment remains. To further assess the impact of tritium releases to the environment upon population cancer rates, the releases and leukaemia rates at the Savannah River site, USA, were compared with the Kruemmel site. Based on the data from 1991 to 1995, the incidence of childhood leukaemia in the vicinity of the Savannah River site was non-significantly less than expected compared with the significantly higher than expected rates close to the German plant. In contrast, tritium releases from the Savannah River site exceed those from the Kruemmel site by several orders of magnitude. The results of this observational study suggest that factors other than environmental tritium releases are associated with the increased number of leukaemia cases near the Kruemmel site.

The causes of acute leukemia

Although impressive biologic advances have increased understanding of leukemogenesis, we know little about the causes of the acute leukemias. Epidemiologic studies have focused primarily on children. Higher birth weight is associated with an increased risk of childhood acute leukemia. Several theories have been advanced that may account for these observations, and additional biologic studies are needed. Some epidemiologic studies suggest that the acute leukemias in children may have an infectious component. Again, further work, especially in the area of specific causative agents, is necessary. Another area for future epidemiologic study includes investigation of exposure to natural and synthetic DNA topoisomerase II inhibitors. Preliminary evidence suggests that exposure to these agents, which are found in certain foods and medications, may be related to the subsequent development of acute leukemia in infants.