Pediatric Exposures to Ionizing Radiation: Carcinogenic Considerations

Children are at a greater risk than adults of developing cancer after being exposed to ionizing radiation. Because of their developing bodies and long life expectancy post-exposure, children require specific attention in the aftermath of nuclear accidents and when radiation is used for diagnosis or treatment purposes. In this review, we discuss the carcinogenic potential of pediatric exposures to ionizing radiation from accidental, diagnostic, and therapeutic modalities. Particular emphasis is given to leukemia and thyroid cancers as consequences of accidental exposures. We further discuss the evidence of cancers that arise as a result of radiotherapy and conclude the review with a summary on the available literature on the links between computer tomography (CT) and carcinogenesis. Appropriate actions taken to mitigate or minimize the negative health effects of pediatric exposures to ionizing radiation and future considerations are discussed.

A review of post-nuclear-catastrophe management

The purpose of this paper is to make radioactive risk more generally understandable. To that end, we compare it to smoking tobacco. Further, we show that the concept of loss of life expectancy permits a quantitative comparison between various aggressions. The demystification of radioactive risk should lead to basic changes in post-catastrophe management, allowing victims to choose whether or not to leave contaminated areas. A less emotional appreciation of radioactive risks should lead to the adaptation of legal practices when dealing with probabilistic situations.

Risk assessment of component failure modes and human errors using a new FMECA approach: application in the safety analysis of HDR brachytherapy

Failure mode, effects and criticality analysis (FMECA) is a safety technique extensively used in many different industrial fields to identify and prevent potential failures. In the application of traditional FMECA, the risk priority number (RPN) is determined to rank the failure modes; however, the method has been criticised for having several weaknesses. Moreover, it is unable to adequately deal with human errors or negligence. In this paper, a new versatile fuzzy rule-based assessment model is proposed to evaluate the RPN index to rank both component failure and human error. The proposed methodology is applied to potential radiological over-exposure of patients during high-dose-rate brachytherapy treatments. The critical analysis of the results can provide recommendations and suggestions regarding safety provisions for the equipment and procedures required to reduce the occurrence of accidental events.

[Medical and biological consequences of nuclear disasters]

Medical risks of radiation exaggerated; psychological risks underestimated. The discussion about atomic energy has become topical again following the nuclear accident in Fukushima. There is some argument about the gravity of medical and biological consequences of prolonged exposure to radiation. The risk of cancer following a low dose of radiation is usually estimated by linear extrapolation of the incidence of cancer among survivors of the atomic bombs dropped on Hiroshima and Nagasaki in 1945. The radiobiological linear-quadratic model (LQ-model) gives a more accurate description of observed data, is radiobiologically more plausible and is better supported by experimental and clinical data. On the basis of this model there is less risk of cancer being induced following radiation exposure. The gravest consequence of Chernobyl and Fukushima is not the medical and biological damage, but the psychological and economical impact on rescue workers and former inhabitants.

Comparison of mortality and incidence solid cancer risk after radiation exposure in the Techa River Cohort

In the present paper, analysis of solid cancer mortality and incidence risk after radiation exposure in the Techa River Cohort in the Southern Urals region of Russia is described. Residents along the Techa River received protracted exposure to ionizing radiation in the 1950s due to the releases of radioactive materials from the Mayak Production Association. The current follow-up through December 2003 includes individuals exposed on the Techa riverside within the Chelyabinsk and Kurgan oblasts using mortality data, and within the Chelyabinsk oblast using incidence data. The analysis was performed by means of the biologically based two-stage clonal expansion (TSCE) model and conventional excess relative risk models. For the mortality and incidence cohorts, central estimates of the excess relative risk per dose of 0.85 Gy(-1) (95% CI 0.36; 1.38) and 0.91 Gy(-1) (95% CI 0.35; 1.52) were found, respectively. For both the mortality and incidence cohorts, the best description of the radiation risk was achieved with the same TSCE model including a lifelong radiation effect on the promotion rate of initiated cells. An increase in the excess risk with attained age was observed, whereas no significant change of risk with age at exposure was seen. Direct comparison of the mortality and incidence cohorts showed that the excess relative risk estimates agreed very well in both cohorts, as did the excess absolute risk and the hazard after correction for the different background rates.

[Causes of death in the Sverdlovsk region's population suffered from emergency radiation situations at the Mayak production association]

Mortality rates were found to increase in three districts of the region (Kamensky, Bogdanovichsky, and Kamyshlovsky ones) after radiation accidents. The highest rate was characteristic of the Kamensky District. A substantial rise in mortality rates was recorded in the first decade following radiation accidents and in the 1980s and 1990s. In these study areas, the change in death rate was most evident for causes, such as circulatory diseases, malignancies, and infectious diseases. An increase in the rates of mortality from perinatal abnormalities and congenital defects was observed in children.

Accidental or intentional exposure to ionizing radiation: biodosimetry and treatment options

The potential risk of accidental and especially intentional radiation exposure in the form of a terrorist attack is growing. The dangers are potentially devastating. There is an urgent need for building a greater infrastructure for teaching and research in this area. Medical contingency planning and preparedness is also essential. Such planning should include an examination of our current resources, projected medical needs, management guidelines, and personnel training. Exposure to whole-body irradiation can induce acute radiation syndrome, with the resultant damage to hematopoiesis and immune suppression. In addition, acute toxicity to the skin, gut, and central nervous system are also prevalent. Complex injuries such as burns, multi-organ injury, and trauma will increase the morbidity and mortality from acute radiation syndrome. Our ability to understand and rapidly obtain data on the absorbed dose and have access to radiation mitigators are of critical importance if we are to have a beneficial impact in the exposed population.

Revisiting therapeutic strategies in radiation casualties

OBJECTIVE

Nuclear/radiological threats have evolved and scenarios for terrorist attacks involving radioactive material have been identified as complex situations. Mass casualty scenarios may happen, and individuals may be exposed to intentionally hidden sources of high activity, resulting in delayed diagnosis and treatment of acute radiation syndrome (ARS). Moreover, ARS must be considered as an emergency in order to better anticipate delayed radiation toxicity. In this context, therapeutic strategies in radiation casualties have to be revisited and new pharmacological approaches developed.

METHODS

B6D2F1 mice were total-body irradiated (TBI) with a 9 Gy gamma dose and then received intraperitoneal doses of either early (stem cell factor + FLT-3 ligand + thrombopoietin + interleukin-3 [SFT3] +/- keratinocyte growth factor (KGF); stem cell factor + erythropoietin + Peg-filgrastim [SEG]) or delayed treatments (SFT3 +/- KGF, erythropoietin, or hyaluronic acid). Survival was monitored and bone marrow hematopoiesis evaluated at 300 days following early treatments.

RESULTS

SFT3 anti-apoptotic cytokine combination administered early (2 hours and 24 hours) after lethal TBI induced 60% survival versus 5% in controls. Early SEG treatment may be an alternative to SFT3 in terms of survival (55%), but SEG benefit might be obtained at the expense of long-term hematopoiesis. SFT3 + KGF induced 75% survival. No effectiveness was observed, over antimicrobial supportive care, when administration of SFT3 or its tested combinations was delayed at 48 hours.

CONCLUSION

As a potentially multi-organ failure, ARS requires global therapy, beyond the hematopoietic syndrome, which may include pleiotropic cytokines such as KGF.

[20-year morpholoogical findings in the study of medical aftereffects of the Chernobyl accident]

Presented are the results of morphological studies of radiation sickness, congenital malformations and malignant tumors which have developed in Chemobyl victims. Until now consequences of the accident remain a subject of practical and research medicine. Scope of relevant topical problems the pathologists will have to investigate in the future is discussed.

[Oncoepidemiologic situation in the Kaluga region of the Russian Federation ten years after the Chernobyl accident]

Cancer morbidity and mortality in radionuclide-contaminated areas of Kaluga Region have been investigated. The study was mainly concerned with the extent of radiation pollution influence on the present-day cancer morbidity and mortality rates. The correlations between the latter factors, on the one hand, and relevant population risks, on the other, have been analysed. It was found that the present-day neoplasm morbidity rates recorded in Chernobyl-stricken areas are chiefly accounted for by a combination of factors which were there before the disaster. The trends of morbidity and mortality from neoplasms of the respiratory tract in females are still unfavorable. There is still no statistical verification of the radiation effect on cancer morbidity except that of thyroid cancer in women in contaminated areas. The morbidity and lethality rates in these areas basically conform to the general trends. The findings are in conformity with those reported worldwide on radiation-related cancer induction latency and biological effects observed in the inhabitants of contaminated regions.

The Chernobyl accident: predicting cardio-vascular disease in the ex-workers

This paper describes a computer package that has been used to predict the likelihood of the onset of cardiovascular diseases in these patients who were former workers (liquidators) on the Chernobyl site in the Ukraine, Chernobyl being the place where the Nuclear Power Station was destroyed when the atomic reactor got out of control and spread radiation over a very wide area both on the ground and into the atmosphere. The programme predicts the future morbidity in those patients with an accuracy of 90%.

[Mortality indices for hemoblastoses in Rivno Province before and after the accident at the Chernobyl Atomic Electric Power Station]

In-depth study of mortality rates for hemoblastoses in Rivno region in which six Northern territories are known to be contaminated with radionuclides, over the period 1981-1991, revealed increase in mortality in postaccident period from hemoblastoses both on the whole and some of its nosologic entities. The statistical analysis of mortality rates for hemoblastoses did not show any significant difference in the corresponding figures between radionuclide contaminated and uncontaminated parts of the Rivno region.

High mortality in the Thule cohort: an unhealthy worker effect

BACKGROUND

The objective was to study mortality in the Thule cohort in order to clarify whether it is a selected population and to ascertain the possibility of misinterpretation when national mortality rates are used as reference in the analysis of occupational mortality.

METHODS

The cohort consists of 4322 Danish men who were employed between 1963 and 1971 at the Thule air base in Greenland. One part of the cohort were employed during the clean-up period after the crash, in 1968, of a US bomber carrying nuclear weapons, the other part had been employed only outside the clean-up period. The cohort was followed up until 1992.

RESULTS

After 30 years of follow-up, SMR was 1.38 for all causes (95% confidence interval [CI]: 1.28-1.49), 1.25 for cancer (95% CI: 1.07-1.45), 1.17 for circulatory diseases (95% CI: 1.01-1.34), 1.58 for other natural causes (95% CI: 1.35-1.84), and 1.46 for violent deaths (95% CI: 1.22-1.74). Marked excess mortality measured by SMR was found from lung cancer 1.70, AIDS 3.55, alcoholism 4.04, cirrhosis of the liver 2.45, symptoms and ill-defined conditions 1.93, and suicide 1.63. The SMR was 1.09 for the age group 17-24 at entry, 1.42 for the age group 25-34, and 1.45 for the age group > or = 35.

CONCLUSIONS

The high mortality and the mortality pattern in the Thule cohort shows strong evidence for selection and provides strong support for the suggestion that these workers constitute a group in poor health probably caused by lifestyle. The study demonstrates that an incomplete analysis (i.e., one limited to a subgroup of workers involved in the radiation clean-up) could lead to spurious conclusions about hazardous occupational exposures.