Radiation-epidemiological studies of thyroid cancer incidence in Russia after the Chernobyl accident (estimation of radiation risks, 1991-2008 follow-up period)

This study presents an analysis of the thyroid cancer incidence in the population of the most contaminated territories of Bryansk, Kaluga, Oryol and Tula oblasts affected by the Chernobyl accident. The follow-up period is 1991-2008, and the cohort size is 309 130 people. For that period 978 thyroid cancer cases were detected. The excess relative risk per 1 Gy (ERR/Gy) is found to be statistically significant for children and adolescents (0-17 y of age) at the time of the Chernobyl accident (ERR/Gy=3.22; 95 % confidence interval (1.56; 5.81). In boys, the ERR/Gy was higher than in girls -6.54 and 2.24, respectively. A statistically significant decrease in ERR/Gy with time since exposure, by a factor of 0.37 per 10 y, was observed for the whole cohort and for boys separately, but not for girls. No radiation risks of a thyroid cancer among people of 18 y of age at exposure and older were found.     

A case-control study of child bicycle injuries: relationship of risk to exposure

In order to assess the relationship of the risk of injury requiring hospital attendance in children riding bicycles to sociodemographic factors and to measures of exposure, a population-based case-control study is being undertaken in a large area of suburban Melbourne, Australia. Particular attention is given to the measurement of individual exposure in several dimensions. Analysis of interim data from 109 cases and 118 controls shows that 51% of injuries occurred while the child was playing rather than making a trip on the bicycle and only 22% involved another vehicle. Boys used bicycles more commonly than girls but there was minimal evidence of an increased risk of injury in boys, adjusting for exposure. There was no evidence for an age trend in injury risk, but children from families in the lowest income category were at significantly increased risk. Exposure measures showed complex patterns of association with injury risk. Estimated time spent riding was more closely associated with risk than distance travelled, with an odds ratio of 2.2 (95% confidence interval 1.1–4.2) for children riding for more than 3 hours per week compared to children riding less than 1 hour. Riding more than 5 km on the sidewalk was also associated with increased risk (odds ratio 3.1, 95% CI 1.1–8.5). The elevated risk associated with sidewalk riding may be due to difficulties in negotiating uneven surfaces. The case-control study provides an ideal design for this type of investigation but valid and reliable measurement of exposure is difficult.     

Radiation dose survey in a paediatric cardiac catheterisation laboratory equipped with flat-panel detectors

Flat-panel X-ray detectors for fluoroscopy represent a modern imaging equipment that is being implemented in paediatric cardiac catheterisation laboratories. Infants and children represent a group of patients with a high radiosensitivity. A survey of 273 (126 diagnostic and 147 therapeutic) paediatric catheterisations was performed to investigate the radiation doses delivered by the new X-ray system. Statistical parameters (75th, 50th and 25th percentiles) of dose-area product (DAP) and fluoroscopy time are reported for patients divided into six age groups: 0-30 d, >1-12 m, >1-3, >3-5, >5-10 and >10-15 y. For accurate risk estimation, effective dose (E) has been determined for all patients using the PCXMC software. For diagnostic procedures, the third quartile of E ranges from 11.3 mSv for newborns to 7 mSv for children of 10-15 y. Therapeutic procedures are more complex than diagnostic. Consequently, the third quartile of E is 22.6 mSv (0-30 d), 18.6 (>1-12 m), 13.3 (>1-3 y), 21.5 (>3-5 y), 17.8 (>5-10 y) and 34.1 mSv (>10-15 y). Dose conversion factors, which relate the DAP and E, have been estimated for each age group. The results of this study may serve as a first step in the optimisation process, in order to make full use of the dose reduction potential of flat-panel systems.     

Leukaemia following childhood radiation exposure in the Japanese atomic bomb survivors and in medically exposed groups

Incidence and mortality risks of radiation-associated leukaemia are surveyed in the Japanese atomic bomb (A-bomb) survivors exposed in early childhood and in utero. Leukaemia incidence and mortality risks are also surveyed in 16 other studies of persons who received appreciable doses of ionizing radiation in the course of treatment in childhood and for whom there is adequate dosimetry and cancer incidence or mortality follow-up. Relative risks tend to be lower in the medical series than in the Japanese A-bomb survivors. The relative risks in the medical studies tend to diminish with increasing average therapy dose. After taking account of cell sterilisation and dose fractionation, the apparent differences between the relative risks for leukaemia in the Japanese A-bomb survivors and in the medical series largely disappear. This suggests that cell sterilisation largely accounts for the discrepancy between the relative risks in the Japanese data and the medical studies. Excess absolute risk has also been assessed in four studies, and there is found to be more variability in this measure than in excess relative risk. In particular, there is a substantial difference between the absolute risk in the Japanese atomic bomb survivor data and those in three other (European) populations. In summary, the relative risks of leukaemia in studies of persons exposed to appreciable doses of ionizing radiation in the course of treatment for a variety of malignant and non-malignant conditions in childhood are generally less than those in the Japanese A-bomb survivor data. The effects of cell sterilisation can largely explain the discrepancy between the Japanese and the medical series.     

Relative radiological risks derived from different TENORM wastes in Malaysia

In Malaysia technologically enhanced naturally occurring radioactive materials (TENORM) wastes are mainly the product of the oil and gas industry and mineral processing. Among these TENORM wastes are tin tailing, tin slag, gypsum and oil sludge. Mineral processing and oil and gas industries produce large volume of TENORM wastes that has become a radiological concern to the authorities. A study was carried out to assess the radiological risk related to workers working at these disposal sites and landfills as well as to the members of the public should these areas be developed for future land use. Radiological risk was assessed based on the magnitude of radiation hazard, effective dose rates and excess cancer risks. Effective dose rates and excess cancer risks were estimated using RESRAD 6.4 computer code. All data on the activity concentrations of NORM in wastes and sludges used in this study were obtained from the Atomic Energy Licensing Board, Malaysia, and they were collected over a period of between 5 and 10 y. Results obtained showed that there was a wide range in the total activity concentrations (TAC) of nuclides in the TENORM wastes. With the exception of tin slag and tin tailing-based TENORM wastes, all other TENORM wastes have TAC values comparable to that of Malaysia's soil. Occupational Effective Dose Rates estimated in all landfill areas were lower than the 20 mSv y(-1) permissible dose limit. The average Excess Cancer Risk Coefficient was estimated to be 2.77×10(-3) risk per mSv. The effective dose rates for residents living on gypsum and oil sludge-based TENORM wastes landfills were estimated to be lower than the permissible dose limit for members of the public, and was also comparable to that of the average Malaysia's ordinary soils. The average excess cancer risk coefficient was estimated to be 3.19×10(-3) risk per mSv. Results obtained suggest that gypsum and oil sludge-based TENORM wastes should be exempted from any radiological regulatory control and should be considered radiologically safe for future land use.     

Childhood leukaemia following medical diagnostic exposure to ionizing radiation in utero or after birth

A statistical association between childhood leukaemia and an abdominal X-ray examination of the pregnant mother was first reported in 1956 from a case-control study of childhood cancer mortality conducted in Great Britain. This study, later called the Oxford Survey of Childhood Cancers (OSCC), was continued and eventually showed a highly statistically significant approximately 50% proportional increase in the risk of childhood leukaemia associated with antenatal diagnostic radiography. The association has been confirmed by many case-control studies carried out around the world, the appropriately combined results of which show a highly statistically significant increase in risk that is compatible with the OSCC finding. There is no doubt about the reality of the statistical association, but a causal interpretation has been questioned. On balance, however, the evidence points to low-level irradiation of the fetus increasing the risk of leukaemia in childhood, with an excess relative risk coefficient of around 50 Gy(-1) (equivalent to an excess absolute risk coefficient of about 3% Gy(-1)), although the uncertainty associated with these coefficients is considerable and they are likely to be overestimates. In contrast to exposure in utero, the evidence from case-control studies for an association between childhood leukaemia and postnatal exposure to medical diagnostic irradiation is equivocal and sometimes conflicting. Since standard radiation risk models predict that low-level exposure in the early years of life should produce an increased risk of childhood leukaemia that is roughly similar to that arising from fetal exposure, this absence of persuasive evidence is likely to be due to various problems with the studies. This is unfortunate given the rise in relatively high dose diagnostic procedures (e.g. paediatric CT scans) that would be predicted to materially increase the relative risk of childhood leukaemia.     

Estimating cancer risks to adults undergoing body CT examinations

The purpose of the study is to estimate cancer risks from the amount of radiation used to perform body computed tomography (CT) examination. The ImPACT CT Patient Dosimetry Calculator was used to compute values of organ doses for adult body CT examinations. The radiation used to perform each examination was quantified by the dose-length product (DLP). Patient organ doses were converted into corresponding age and sex dependent cancer risks using data from BEIR VII. Results are presented for cancer risks per unit DLP and unit effective dose for 11 sensitive organs, as well as estimates of the contribution from 'other organs'. For patients who differ from a standard sized adult, correction factors based on the patient weight and antero-posterior dimension are provided to adjust organ doses and the corresponding risks. At constant incident radiation intensity, for CT examinations that include the chest, risks for females are markedly higher than those for males, whereas for examinations that include the pelvis, risks in males were slightly higher than those in females. In abdominal CT scans, risks for males and female patients are very similar. For abdominal CT scans, increasing the patient age from 20 to 80 resulted in a reduction in patient risks of nearly a factor of 5. The average cancer risk for chest/abdomen/pelvis CT examinations was ～26 % higher than the cancer risk caused by 'sensitive organs'. Doses and radiation risks in 80 kg adults were ～10 % lower than those in 70 kg patients. Cancer risks in body CT can be estimated from the examination DLP by accounting for sex, age, as well as patient physical characteristics.     

Radiation protection dosimetry for diagnostic radiology patients

The radiation protection of patients undergoing medical X-ray examinations is governed by the principles of justification and optimisation. Radiation dosimetry is required to inform medical practitioners of the levels of exposure and hence the risks from the diagnostic procedures that they have to justify and to assist the operators of X-ray imaging equipment to determine whether their procedures are optimised. This paper describes the main dosimetric methods that have been developed to meet these requirements. Suitable radiation risk projection models are used to predict the risks to patients in the UK from computed tomography examinations, as a function of age at exposure and sex, and show that the lifetime risk of fatal cancer can reach 1 in 1000 for children. The concept of 'diagnostic reference levels' as an aid to the optimisation of medical exposures is described, and progress in implementing them in the UK is reported.     

Factors associated with fatal and injurious car crash among learner drivers in New South Wales,Australia

This exploratory study investigated factors associated with car crash injury among learner drivers across difference ages by using data routinely collected by the NSW police. The results obtained indicated that some factors are commonly associated with car crash injury across nearly all ages. On the other hand, some others are more age specific. On the whole, female learner drivers were more at risk of being killed or injured as compared to males. The drivers of 16 years old had an increased risk of crash injury due to environmental factors, such as special road feature, and distraction outside the vehicle. The increased risk of crash injury for older drivers (> or =25 years) was associated with distractions from both inside and outside vehicle. Night time driving posed a special risk to learner drivers aged 20-24 years old, but not other age groups. Speeding was a common factor for the increased risk of crash injury across all age groups. The implication of the results and limitations of the study were discussed.     

Health Canada's approach to manage risks to populations at risk during a radiological emergency

The approach that Health Canada uses to manage risks to individuals and to populations who might be exposed to ionising radiation is based upon the risk management paradigm. The paradigm differs little between an emergency and a non-emergency situations. In both events, technical experts assess the risk by determining the exposure to the source of radiation. They usually calculate the radiation dose and then assess the potential for any health effects. The initial technical assessments often use scoping calculations. The calculations for children recognise that they are smaller and have different metabolic rates and different behaviour from adults. However, most rigorous quantitative models for dosimetry do not differentiate between children and adults. The risk assessments that were conducted to evaluate the contamination of Canadians who were in London during the Litvenenko poisoning are a good example to illustrate this general approach. The scoping risk assessment concluded that the risks to children and adults were low. No Canadian children were exposed to polonium during this event and, to date, there have been no radiation emergencies in Canada where children have been exposed to a significant source of radiation. Therefore, the comparisons between theory and practice are very limited and conclusions are drawn from international experience and other incidents or sources of radiation exposure such as radon and medical exposures.     

'Lifestyle' and cancer rates in former East and West Germany: the possible contribution of diagnostic radiation exposures

Breast and prostatic cancer as well as leukaemia in childhood have remarkably increased over some decades in the Federal Republic of Germany as well as in several other highly developed industrial nations. Such increase was much less or not observable in East Germany between 1960 and 1989 where diagnostic exposures were applied to a lesser extent. Low-level radiation can cause these diseases and the difference of cancer rates gives rise to renewed evaluation of current risk estimates. Risk factors for radiation-induced childhood leukaemia and breast cancer are derived from the literature, considering a higher relative biological effectiveness of diagnostic X rays in comparison to the A-bomb gamma rays in Hiroshima and Nagasaki. The prostate is not considered as radiation sensitive by the ICRP. But following a variety of low-level findings in the last two decades it was shown by Myles et al. in the UK that prostatic cancer is inducible by diagnostic X-ray procedures. From their study in men below the age of 60, a doubling dose of about 20 mSv can be estimated. Medical exposures of the considered tissues are taken from published data for East and West Germany. The difference in breast cancer mortality can be explained by diagnostic exposures. The contribution of these to prostatic cancer and childhood leukaemia must be regarded as relevant in current incidences. Reduction of diagnostic exposures would be an important measure for preventing several prominent cancer diseases.     

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.     

Aetiology of childhood acute leukaemias: current status of knowledge

Acute leukaemia is a consequence of malignant transformation of a haematopoetic progenitor cell. Molecular studies have revealed a prenatal origin of many childhood leukaemias. According to current models, a preleukaemic stem cell clone is generated by a first mutation in utero which, in a minority of children, progresses to leukaemia after receiving further postnatal genetic hits. The nature of pre- and postnatal events involved in leukaemogenesis in children is not well understood. Although genetic predisposition and specific environmental exposures may account for individual cases, the bulk of childhood leukaemia cannot be explained by any of these factors. The higher incidence of the most common leukaemia subtype in affluent societies, as well as the age peak between 2-5 y, suggest a contributory role of socioeconomic factors. An abnormal immune response during delayed exposure to common infections provides a plausible mechanism for malignant progression of preleukaemic clones in a subgroup of children. As highlighted in this review, a common cause for all types and subtypes of childhood leukaemia is highly unlikely. Deeper insights into the pathogenesis of childhood leukaemia will rely on large-scale and combined epidemiological and biomolecular studies.     

Risk estimates for meningiomas and other late effects after diagnostic X-ray exposure of the skull

This study aims to investigate the contribution of diagnostic exposures to the rising rates of brain tumours and other neoplasms which are observed in several industrial nations. Included are benign tumours in the head and neck region and cataracts which are neglected in usual risk estimates by international and national radiation protection committees. Dose-effect relationships for tumours of the brain, skin, thyroid and other sites of the head region, leukaemia and cataracts are taken from the literature. Risk estimates are derived for paediatric head computed tomographies (CTs) as well as for brain tumours in adults. On the basis of estimates for Germany about the number of head scans, the annual rate of radiation-induced diseases is calculated. About 1000 annual paediatric CT investigations of the skull will lead to about three excess neoplasms in the head region, i.e. the probability of an induced late effect must be suspected in the range of some thousands. Additionally, a relevant increase of cataracts must be considered. The radiation-induced occurrence of meningiomas and other brain tumours most probably contributes to the continuously increasing incidence of these diseases which is observed in several industrial nations, as well as the exposure of the bone marrow by CT to the increase of childhood leukaemia.     

Younger black patients have a higher risk of infection mortality that is mostly non‐dialysis related: A national study of cause‐specific mortality among U.S. maintenance dialysis patients

Introduction: While it has been well documented that in the U.S., black and Hispanic dialysis patients have overall lower risks of death than white dialysis patients, little is known whether their lower risks are observed in cause‐specific deaths. Additionally, recent research reported that younger black patients have a higher risk of death, but the source is unclear. Therefore, this study examined cause‐specific deaths among US dialysis patients by race/ethnicity and age. Methods: This national study included 1,255,640 incident dialysis patients between 1995 and 2010 in the United States Renal Data System. Five cause‐specific mortality rates, including cardiovascular (CVD), infection, malignancy, other known causes (miscellaneous), and unknown, were compared across blacks, Hispanics, and whites overall and stratified by age groups. Findings: After multiple adjustments, Hispanic patients had the lowest risk of mortality for every major cause in almost all ages. Compared with whites, blacks had a lower risk of death from CVD, malignancy and miscellaneous causes in most age groups, but not from infection. In fact, blacks had a higher risk of infection death than whites in ages 18–30 years (HR [95% CI] 1.94 [1.69–2.23]; P < 0.001), 31–40 years (HR 1.51 [1.40–1.63]; P < 0.001) and 41–50 years (HR 1.07 [1.02–1.12]; P = 0.009), which were partially attributed to their higher prevalence of AIDS nephropathy. For each race/ethnicity, more than two‐thirds of infection deaths were due to non‐dialysis related infections. Discussion: Hispanics had the lowest risk for each major cause of death. Blacks were less likely to die than whites from most causes, except infection. The previously reported higher overall mortality rate for younger blacks is attributed to their two‐fold higher infection mortality, which is mostly non‐dialysis related, suggesting a new direction to improve their overall health status. Research is greatly needed to determine social and biological factors that account for the survival gap in dialysis among different racial/ethnic groups.     

Family planning and the health of women and children

Use of family planning has the potential to produce reductions of 10–20% in infant and child mortality. Similar reductions in the mortality rate associated with pregnancy can be expected for mothers. A larger impact on maternal mortality is possible through fertility reduction with decreased exposure to the risks of pregnancy. First births carry excess risks for mothers and children, but these are, by definition, unavoidable. Births to young mothers also pose increased risks for mothers and children. High birth order and older age of mothers probably have been overemphasized as risk factors for children. Very high parity does pose risks to mothers. Poor spacing of births is associated with increased health risks to children. Estimation of mortality reduction through family planning requires knowledge of risk distribution as well as relative risk. High-risk births are relatively rare, and most deaths occur to mothers and babies at average or low risk. Family planning does not avert all high-risk pregnancies because of a lack of acceptance and imperfect use.     

Dosimetric characteristics of Li2B4O7:Cu,Ag,P solid TL detectors

A two-mutation carcinogenesis (TMC) model is used as a bridge between cellular radiation biological effects and the incidence of cancer. This model has been applied to several sets of experimental animal and epidemiological data. In this paper the advantage of the model and the implications for radiation risks at low doses are discussed with respect to the age and dose dependence of cancer incidence and the effect of age at exposure on radiation risk; the link between the radiation effect and background cancer incidence and the transfer of radiation risk across different population groups; the implications of acute and protracted radiation exposures for risks at low doses and the dose-effect relationship for radium induced bone cancer.     

A review of some epidemiological studies on cancer risk from low-dose radiation or other carcinogenic agents

It is extremely difficult to assess cancer risks accurately due to health effects of low-dose radiation exposure or other carcinogens based on epidemiological studies. For the detection of minute increases of the risk at low-level exposure, most of epidemiological studies lack statistical power, and they involve various complicated confounding factors. This paper reports on a literature survey of epidemiological studies published since 2000 on cancer risks associated with low-dose radiation and other carcinogens to gather major epidemiological data. Integrated risk indices were derived from those data by using, where possible, statistical models. Regarding risk assessment of low-dose radiation exposure, it is important to lower the degree of uncertainty arising from risk estimation. Risk assessment of low-dose radiation exposure could be scientific evidence when uncertainty is considered in comparing carcinogenic risks of radiation with those of other carcinogens.     

Evidence of children's vulnerability to radiation in the context of radiological/nuclear events and considerations for emergency response

International organisations, such as International Atomic Energy Agency, United Nations Scientific Committee on the Effects of Atomic Radiation and World Health Organisation, together with committees of experts such as Biological Effects of Ionising Radiation and Committee on Medical Aspects of Radiation in the Environment, have assessed the effects of radiation on large exposed populations (Chernobyl accident, and Hiroshima/Nagasaki atomic bombings) and on nuclear energy workers and people living near nuclear facilities. Childhood and in utero exposure to moderate and high levels of ionizing radiation, such as those experienced during the atomic bombings of Japan, or from radiotherapy, is an established cause of leukaemia and solid cancer. There is no evidence of increase in solid cancers (excluding thyroid cancer) or leukaemia in the children from Chernobyl, and no evident link between worker's exposure to radiation and leukaemia in their offspring or with the presence of leukaemia clusters around nuclear power plants. It has also not been possible to demonstrate the evidence of radiation hereditary effects in human populations. In accordance with international guidance, Canadian Nuclear Safety Commission recommends optimisation of protection strategies to reduce doses to children. The development of credible radiological/nuclear event scenarios would assist in identifying probable sources of radioactivity and pathways of exposure for children. Such scenarios should then be used to identify protection strategies appropriate for children.