Fallout from Chernobyl and incidence of childhood leukaemia in Finland, 1976-92.

OBJECTIVE--To assess effects of fallout from Chernobyl on incidence of childhood leukaemia in Finland. DESIGN--Nationwide cohort study. External exposure measured for 455 Finnish municipalities with instruments driven 19,000 km throughout the country. Values specific to municipalities corrected for shielding due to houses and fallout from A bomb testing. Internal exposure estimated from whole body measurements on a random sample of 81 children. Mean effective dose for two years after incident calculated from these measurements. Data on childhood leukaemia obtained from Finnish cancer registry and verified through hospitals treating childhood cancers. SETTING--Finland, one of the countries most heavily contaminated by the Chernobyl accident; the population was divided into fifths by exposure. SUBJECTS--Children aged 0-14 years in 1976-92. MAIN OUTCOME MEASURES--Standardised incidence ratio of childhood leukaemia and relative excess risk of childhood leukaemia per mSv. From incidence data of Finnish cancer registry for 1976-85, expected numbers specific to sex and age group (0-4, 5-9, and 10-14 years) were calculated for each municipality for three periods (1976-85, 1986-8, and 1989-92) and pooled as exposure fifths. Dose response was estimated as regression slope of standardised incidence ratios on mean doses for fifths for each period. RESULTS--Population weighted mean effective doses for first two years after the accident were 410 microSv for the whole country and 970 microSv for the population fifth with the highest dose. In all Finland the incidence of childhood leukaemia did not increase 1976-92. The relative excess risk 1989-92 was not significantly different from zero (7% per mSv; 95% confidence interval -27% to 41%). CONCLUSIONS--An important increase in childhood leukaemia can be excluded. Any effect is smaller than eight extra cases per million children per year in Finland. The results are consistent with the magnitude of effect expected.     

Neonatal vitamin K administration and childhood cancer in the north of England: retrospective case-control study.

OBJECTIVE: To explore the possible association between intramuscular vitamin K given to neonates and the subsequent development of childhood cancer. DESIGN: Retrospective case-control study on the basis of hospital records. SETTING: The former Northern Health region of England. SUBJECTS: 685 children who were born and lived in the region and who developed cancer before their 15th birthday, and 3442 controls also born between 1960 and 1991 and matched only for date and hospital of birth. The notes of a further 701 index cases were untraceable. MAIN EXPOSURE MEASURE: Administration of intramuscular vitamin K versus no exposure to vitamin K. RESULTS: There was no association between the administration of vitamin K and the development of all childhood cancers (unadjusted odds ratio 0.89; 95% confidence interval 0.69 to 1.15) or for all acute lymphoblastic leukaemia (1.20; 0.75 to 1.92), but there was a raised odds ratio for acute lymphoblastic leukaemia developing 1-6 years after birth (1.79; 1.02 to 3.15). No such association was seen in a separate cohort-based study not dependent on case note retrieval in which the rates of acute lymphoblastic leukaemia in children born in hospital units where all babies received vitamin K were compared with those born in units where less than a third received prophylaxis. CONCLUSIONS: It is not possible, on the basis of currently published evidence, to refute the suggestion that neonatal intramuscular vitamin K administration increases the risk of early childhood leukaemia. Any association may have been masked in earlier studies that did not use controls matched for time and locality by other unidentified factors affecting the spatiotemporal variations in incidence of leukaemia.     

Trends in childhood leukaemia in the Nordic countries in relation to fallout from atmospheric nuclear weapons testing.

OBJECTIVE--To obtain further information about the risks of childhood leukaemia after exposure to ionising radiation at low doses and low dose rates before or after birth or to the father''s testes shortly before conception. DESIGN--Observational study of trends in incidence of childhood leukaemia in relation to estimated radiation exposures due to fallout from atmospheric nuclear weapons testing during the 1950s and 1960s. SETTING--Nordic countries. SUBJECTS--Children aged under 15 years. MAIN OUTCOME MEASURES--Incidence rates of leukaemia by age at diagnosis, sex, country, and calendar year of diagnosis or year of birth; exposure category; relation between leukaemia and exposure for children aged 0-14 and 0-4 separately. RESULTS--During the high fallout period the average estimated dose equivalent to the fetal red bone marrow was around 140 mu Sv and the average annual testicular dose 140 mu Sv. There was little evidence of increased incidence of leukaemia among children born in these years. Doses to the red bone marrow of a child after birth were higher, and during the high exposure period children would have been subjected to an additional dose equivalent of around 1500 mu Sv, similar to doses received by children in several parts of central and eastern Europe owing to the Chernobyl accident and about 50% greater than the annual dose equivalent to the red bone marrow of a child from natural radiation. leukaemia incidence and red marrow dose was not related overall, but rates of leukaemia in the high exposure period were slightly higher than in the surrounding medium exposure period (relative risk for ages 0-14: 1.07, 95% confidence interval 1.00 to 1.14; for ages 0-4: 1.11, 1.00 to 1.24). CONCLUSIONS--Current predicted risks of childhood leukaemia after exposure to radiation are not greatly underestimated for low dose rate exposures.     

Vitamin K and childhood cancer: a population based case-control study in Lower Saxony,Germany.

OBJECTIVE--To confirm or refute a possible association of parenteral vitamin K prophylaxis and childhood cancer. DESIGN--Population based case-control study. Comparison of vitamin K exposure in children with leukaemia or other common tumours with two control groups. SETTING--State of Lower Saxony (north western part of Germany); case recruitment from the German childhood cancer registry. SUBJECTS--272 children with leukaemia, nephroblastoma, neuroblastoma, rhabdomyosarcoma, and tumours of the central nervous system diagnosed between 1 July 1988 and 30 June 1993; children were aged between 30 days and 15 years at diagnosis. 334 population based controls without diagnoses of cancer matched to the leukaemia cases for age and sex. MAIN EXPOSURE MEASURES--Parenteral vitamin K prophylaxis (intramuscular and subcutaneous) versus oral and no vitamin K prophylaxis. RESULTS--An association between parenteral vitamin K exposure and childhood cancer (leukaemias and other tumours combined) could not be confirmed (odds ratio 1.04, 95% confidence interval 0.74 to 1.48). For leukaemias the observed odds ratio was only 0.98 (0.64 to 1.50) (comparison of leukaemia cases with local controls 1.24 (0.68 to 2.25); state controls 0.82 (0.50 to 1.36)). These odds ratios remained almost unchanged when several potential confounders were considered in the logistic regression model. CONCLUSIONS--This population based study adds substantial evidence that there is no association between parenteral vitamin K and childhood cancer.     

15 years after the accident at the Chernobyl Nuclear Power Plant

Health effects as a result of the accident at the Chernobyl nuclear power plant occurred in 1986 are considered in the paper. Wrong prognosis of the health effects with respect to mortality and morbidity among the population exposed to low radiation doses is shown. Proven increase in thyroid cancer cases among people who were children aged from 0 to 18 at the time of the accident is shown. Linear relationship between thyroid cancer cases and dose to thyroid ranged from 0.2 to 4.0 Gy is considered. An additional absolute risk of thyroid cancer in children varies in the range 1.9-2.6 cases per 10(4) person-year Gy. During the fifteen years following the accident no cases of acute and chronic radiation sickness have been revealed because the population living in contaminated areas received low radiation doses. Also, exposures to low radiation doses did not result in excess of malignant tumors among population. In some cases the outcomes of acute radiation sickness were as follows: radiation damages to the skin, cancer cataracts, development of oncopathology.     

The effect of Chernobyl accident on the development of malignant diseases--situation after 20 years

The accident that occurred at the Chernobyl Nuclear Power Plant in 1986, released large quantities of radionuclides--among them radioiodine--into the atmosphere, thereby raising public concerns about its influence on thyroid structure and function, especially the development of malignancy. There were even reports about 700 deaths due to thyroid carcinoma in Russian Federation, Ukraine and Belarus, resulting from the accident. In this review we discussed the incidence of thyroid cancer in different parts of the world, especially in heavily contaminated countries, as Ukraine and Belarus, and the possible link between radioisotope activity in the thyroid and the development of malignancy. The study carried out in Minsk showed 40-fold increase of the incidence of thyroid cancer in the years 1986-1994, in comparison to the period 1977-1985. An increase of the incidence of thyroid cancer has generally been observed in many countries after the Chernobyl accident. We focused on the factors that may have an influence on this phenomenon, especially diagnostic tests, health care, social and environmental factors, like iodine level in water and soil. The results of molecular biology studies, e.g. RET translocation in carcinoma type RET/PTC1 in elderly and RET/PTC3 in children, and expression Ax1 and Gas6 in children were reviewed as well. We also mentioned other thyroid diseases, like nodular goitre, cysts, the disturbance of thyroid function and autoimmunity, possibly linked to the radiation after Chernobyl accident. Data obtained from the regions near Chernobyl showed no increased risk of other types of malignancy (leukaemia, Hodgkin's and non Hodgkin's lymphoma) in 1986-1996. In this article the epidemiology of thyroid diseases in Poland was also reviewed.     

Distribution of Acute Leukaemia in Time and Space. Studies in New Zealand

The distribution of leukaemia in time and space was examined by tracing the date of onset and the place of residence in all cases of childhood leukaemia and of acute leukaemia in adults, totalling 1,003 cases, which occurred in New Zealand during the 12 years from 1953 to 1964.Significant seasonal variations in the onset were found in adults but not in children. Time-space clustering did not occur in adults, but a significant tendency towards it was found in children aged less than 6 years. Since a similar tendency has previously been found by two other groups of investigators it is suggested that leukaemia in young children may have a different aetiology from that occurring at other ages.     

Age specific formation of doses in children exposed to radioactive caesium following the accident in the Chernobyl Nuclear Power Plant

Individual measurement data on radiological surveillance of people residing in the territories most radioactively contaminated following the Chernobyl accident are analyzed to provide a comparison of doses from caesium radionuclides to children and adults. The external doses to children does not exceed those to adult inhabitants of the same settlement. By the results of surveillance in 1986 more than 80 thousand inhabitants of the western areas of Bryansk region, a specific activity of caesium radionuclides and corresponding internal radiation dose rate in a number of settlements appeared at children age under 3 years old exceeding the appropriate parameters for adult inhabitants. Among persons evacuated from the contaminated areas, such excess in day of departure from an area averaged 3.8 for surveyed pairs the child-parent.     

The effect of Chernobyl accident on the development of non malignant diseases

The early medical complications of Chernobyl accident include post radiation disease, which were diagnosed in 134 subjects affected by ionizing radiation. 28 persons died during the first 100 days after the event. The increase occurrence of coronary heart disease, endocrine, haematological, dermatological and other diseases were observed after disaster in the contaminated territories. We also discussed the impact of ionizing radiation from Chernobyl accident on pregnancy and congenital defects occurrence. Changes following the Chernobyl accident, as the inhabitants migration from contaminated regions, political and economic conversions, led to depression, anxiety, and even to "epidemic" of mental diseases. Increased suicide rate, car accidents, alcohol and drug abuse have been observed in this population. Nowadays vegetative neurosis is more often diagnosed in Ukrainian children. Epidemiological studies were conducted on the ionising radiation effect on the health and on the dose of received radiation after Chernobyl accident face numerous problems as the absence of reliable data regarding diseases in the contaminated territories.     

Dietary habits during the 2 months following the Chernobyl accident and differentiated thyroid cancer risk in a population-based case–control study

BackgroundThe Chernobyl nuclear power plant accident occurred in Ukraine on April 26th 1986. In France, the radioactive fallout and thyroid radiation doses were much lower than in highly contaminated areas. However, a number of risk projections have suggested that a small excess in differentiated thyroid cancer (DTC) might occur in eastern France due to this low-level fallout. In order to investigate this potential impact, a case–control study on DTC risk factors was started in 2005, focusing on cases who were less than 15 years old at the time of the Chernobyl accident. Here, we aim to evaluate the relationship between some specific reports of potentially contaminated food between April and June 1986 – in particular fresh dairy products and leafy vegetables – and DTC risk.MethodsAfter excluding subjects who were not born before the Chernobyl accident, the study included 747 cases of DTC matched with 815 controls. Odds ratios were calculated using conditional logistic regression models and were reported for all participants, for women only, for papillary cancer only, and excluding microcarcinomas.ResultsThe DTC risk was slightly higher for participants who had consumed locally produced leafy vegetables. However, this association was not stronger in the more contaminated areas than in the others. Conversely, the reported consumption of fresh dairy products was not statistically associated with DTC risk.ConclusionBecause the increase in DTC risk associated with a higher consumption of locally produced vegetables was not more important in the most contaminated areas, our study lacked power to provide evidence for a strong association between consumption of potentially contaminated food and DTC risk.     

Trends in infant leukaemia in West Germany in relation to in utero exposure due to the Chernobyl accident

A temporary increase in the incidence of infant leukaemia in Greece was reported by Petridou et al., which was attributed to in utero exposure to ionising radiation resulting from the Chernobyl accident. We performed a similar analysis based on the data of the German Childhood Cancer Registry in order to check whether the observation could be confirmed by means of independent data. Applying the same definitions as Petridou et al., we also observed an increased incidence of infant leukaemia in a cohort of children born after the Chernobyl accident. More detailed analyses, regarding areas with different contamination levels and dose rate gradients over time after the accident, showed, however, no clear trend with regard to exposure. It would therefore appear less likely that the observed effect was caused by exposure to ionising radiation due to the Chernobyl accident. Received: 30 January 1998 / Accepted in revised form: 23 April 1998     

Effect of population mixing and socioeconomic status in England and Wales, 1979-85, on lymphoblastic leukaemia in children.

OBJECTIVE: To examine the effects of migration, diversity of migrant origins, commuting, and socioeconomic status on the incidence of acute lymphoblastic leukaemia in childhood. DESIGN: Poisson regression analysis of incidence rates in relation to the variables of interest. SETTING: The 403 county districts of England and Wales during 1979-85. SUBJECTS: Children aged under 15 years. RESULTS: There were significant trends in the incidence of lymphoblastic leukaemia at ages 0-4 and 5-9 years with the proportion of children in a district who had recently entered the district. While there was no consistent relation between the proportion of recent incomers in the total population of a district and its incidence rate, the combination of higher migration with greater diversity of origins or distance moved was associated with higher incidence in both age groups. Incidence increased significantly at age 0-4 with the level of employment in a district and at age 5-9 with the proportion of households with access to a car. No significant trends were found with commuting. CONCLUSIONS: The results for level of child migration and diversity of total migration provide evidence of an effect of population mixing on the incidence of childhood leukaemia which is not restricted to areas experiencing the most extreme levels of mixing.     

Population based survival rates for childhood cancer in Britain, 1980-91.

OBJECTIVES--To investigate the survival of children with cancer diagnosed during 1980-91 in order to assess the impact of developments in medical care on a population basis. DESIGN--Retrospective cohort study. SETTING--Great Britain. SUBJECTS--14973 children with cancer diagnosed during 1980-91 and included in the population based National Registry of Childhood Tumours. MAIN OUTCOME MEASURES--Actuarial survival rates. RESULTS--For all cancers combined, two year survival increased from 66% to 76% between 1980-2 and 1989-91, and five year survival increased from 57% to 65% between 1980-2 and 1986-8. Significant increases in survival rates occurred among children with acute lymphoblastic leukaemia, acute nonlymphocytic leukaemia, retinoblastoma, osteosarcoma, Ewing''s sarcoma, rhabdomyosarcoma, and malignant gonadal germ cell tumours. No trend in survival was seen for children with Hodgkin''s disease, central nervous system tumours, neuroblastoma, or Wilms''s tumour. CONCLUSIONS--Nearly two thirds of children who have cancer diagnosed can now expect to survive at least 10 years.     

Mutation rates in scots pine (Pinus sylvestris L.) from the Chernobyl exclusion zone evaluated with amplified fragment-length polymorphisms (AFLPs) and microsatellite markers

Ionizing radiation is a strong mutagenic factor and, accordingly, elevated mutation rates would be expected in plants exposed to high chronic or acute radiation after the Chernobyl accident in 1986. Somatic mutations were analyzed in pines (Pinus sylvestris L.) planted before and after the Chernobyl accident and in control material of the same origin planted in sites with natural radiation. Microsatellites (SSRs) and amplified fragment-length polymorphisms (AFLPs) were investigated. The mutation rates for microsatellites were estimated as 2.8 × 10(-4)-7.1 × 10(-4) per locus for different irradiated tree populations; no mutations were detected in the controls. In the case of AFLPs, the observed mutation rates were 3.74 × 10(-3) -3.99 × 10(-3) and 1.06 × 10(-3) per locus for contaminated and control areas, respectively. Thus a statistically highly significant three-fold increase in number of mutations was found by the use of AFLP markers, indicating that ionizing radiation causes strong DNA damage across the entire genome and that AFLPs may be the appropriate marker system for this kind of analysis.     

Analysis of blood lymphocyte subsets in children living around Chernobyl exposed long-term to low doses of cesium-137 and various doses of iodine-131

Epidemiological studies have found that children living around Chernobyl have rates of respiratory tract illness that are higher than those seen in the area before the Chernobyl accident. The present study investigates the possible effects of radiation exposure on the composition of peripheral blood lymphocyte subsets in children living around Chernobyl. Two hundred nineteen healthy children and children suffering from recurrent respiratory diseases aged 6-14 years who received both low doses of radiation to the whole body from (137)Cs and various doses of radiation to the thyroid from (131)I as fallout from the accident were assessed 5 (1991) and 8-10 years (1994-1996) after the accident. A total of 148 healthy children and children suffering from recurrent respiratory diseases living in noncontaminated areas were also evaluated as controls. Children with recurrent respiratory diseases who lived around Chernobyl had a significantly lower percentage of T cells and a higher percentage of NK cells compared to control children with recurrent respiratory diseases during the study period. In contrast to the findings in 1991, a significant decrease in the percentage of helper-inducer cells was observed in children with recurrent respiratory diseases in 1994-1996. In contrast to 1991, there is a positive correlation between the percentage of helper-inducer cells, the helper-inducer/cytotoxic-suppressor cell ratio, and the dose of radiation to the thyroid of healthy children from (131)I in 1994-1996. There was a positive correlation between the dose of radiation to the thyroid from (131)I and the percentage of helper-inducer cells in children with recurrent respiratory diseases 5 years (1991) after the accident. Further, the dose of radiation to the thyroid from (131)I correlated negatively with the percentage of T and B cells and positively with the percentage of NK cells in children with recurrent respiratory diseases 8-10 years (1994-1996) after the accident. These results raise the possibility that long-term exposure to low doses of (137)Cs may have altered the composition of the T-cell subsets and NK cells in children with recurrent respiratory diseases. The differences in the composition of the peripheral blood lymphocyte subsets between healthy children and those with recurrent respiratory diseases may be attributed to long-term low-dose exposure of the whole body to radiation from (137)Cs and exposure of the thyroid to radiation from (131)I subsequent to the Chernobyl accident.     

Bronchiectasis in acute leukaemia.

Five children in remission from acute lymphoblastic leukaemia developed bronchiectasis when on chemotherapy. Persistent collapse or consolidation on chest radiographs was helpful in suggesting the diagnosis. Necropsy established the diagnosis in one child who died of massive haemoptysis when in complete remission, and bronchography confirmed the diagnosis in three. In a further child the diagnosis was based on clinical and chest X-ray findings alone. The surviving children were treated with prophylactic rotating antibiotics. Routine chest radiographs are recommended in children with acute lymphoblastic leukaemia, as bronchiectasis may otherwise be underdiagnosed.     

Wartime evacuation and mortality from childhood leukaemia in England and Wales in 1945-9.

OBJECTIVE--To discover whether the wartime government evacuation of children from London and other population centres to rural districts was associated with any increase in childhood leukaemia. DESIGN--Observational study of mortality from leukaemia among the childhood population of England and Wales in relation to the unique population movements during the second world war. The 476 rural districts of England and Wales were ranked according to the ratio of government evacuees (two thirds of them children) to local children in September 1941. The districts were divided into three categories, each with similar numbers of children in 1947 but with different ratios of evacuees to local children ("low," "intermediate," "high"). Mortality from childhood leukaemia was examined in these three rural categories in 1945-9. Urban areas were also examined according to their exposure to evacuees. SETTING--Local authority areas of England and Wales. SUBJECTS--Children aged under 15. RESULTS--47% excess of leukaemia at ages 0-14 years occurred in 1945-9 in the rural "high" category for evacuees relative to the "low" category, with a significant trend across the three categories. There were increases in both the 0-4 and 5-14 year age groups, but these were larger in the older age group. Rates 25% lower than average occurred in rural areas with few evacuees. CONCLUSION--These findings suggest that wartime evacuation increased the incidence of childhood leukaemia in rural areas and that other forms of population mixing may have contributed to the increases in past decades. Overall, they add to the appreciable evidence for an infective basis in childhood leukaemia.