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The article examines the common descriptive models for radiation risk with a view towards assessing probability of causation (POC). It discusses various statistical and epidemiological issues that should be considered in estimating radiation causation such as the joint effects of radiation and smoking in lung cancer. The relationship between relative risk and attributable risk for radiation in the presence of other risk factors are also mentioned.

The article discusses the status and issues on low-dose radiation epidemiology studies. It notes that epidemiologic studies of human populations with low-dose or low dose-rate exposures are one approach to address key radiation protection concerns. In terms of occupational and medical radiation protection, identification of individuals who are susceptible to radiation cancer induction is of high interest. A comparison between a number of studies of radiation workers, medical radiation exposures, and the Japanese atomic bomb study are discussed.

The article investigates the estimation of time and age effect-modification of radiation-induced cancer risks among atomic bomb survivors. In radiation risk assessment based on follow-up data, estimation of excess relative cancer rate involves evaluation of effect modification by time-related factors such as age at exposure, time since exposure and attained age. In summary, model coefficients for time-since-exposure, age-at-exposure, and attained-age effects on radiation-induced cancer risks among atomic bomb survivors and other cohort studies estimate combined effects.

To obtain the best statistical model for a previous study of cataract prevalence in atomic-bomb survivors, we tested the fitness of the threshold model in an updated dataset of the study, utilizing re-diagnosis by a single ophthalmologist, use of the DS02 dosimetry system, and separation of the in utero group. The results suggest that, in 730 atomic-bomb survivors, we cannot conclude thresholds are greater than 0 Sv in cortical cataract and posterior sub-capsular opacity since the lower 90% confidence limits of the thresholds were 0 Sv. Threshold dose point estimates were 0.6 Sv (90% CI, <0.0-1.2 Sv) and 0.7 Sv (90% CI, <0.0-2.8 Sv) for cortical cataract and posterior sub-capsular opacity, respectively. Detailed regression analyses with no threshold model showed that nuclear color and nuclear opacity have no dose responses (p > 0.40). Cortical cataract showed a significant dose effect (p = 0.002), with an odds ratio (OR)/Sv of 1.30 (95% CI, 1.10-1.53) and no dose-effect modifiers. Posterior sub-capsular opacity showed a significant dose effect (p < 0.001), with an OR/Sv of 1.44 at age of exposure of 10 y (95% CI, 1.19-1.73). The dose effect decreased significantly with increasing age at exposure (p = 0.022). No dose response was observed for in utero survivors (p > 0.20). [ABSTRACT FROM AUTHOR]

The Department of Veterans Affairs identifies 195,000 servicemen as being involved in the occupation of Hiroshima and Nagasaki, with an additional 210,000 personnel participating in 200 post-war nuclear tests. In 1995, the Institute of Medicine declined to recommend a study of the reproductive outcomes of Atomic Veterans. This article revisits the Institute of Medicine decision. Health effects and legislation provide the framework for a critical analysis of the Japanese data as it applies to Atomic Veterans. It explores the role of traditional hypothesis testing in legislative decisions and offers an in-depth exploration of paternal contributions to adverse reproductive events. It emphasizes the risks faced by reproductive age males when exposed to environmental hazards such as ionizing radiation. [ABSTRACT FROM AUTHOR]

Cancer incidence and mortality data from the atomic bomb survivors cohort has been analyzed to allow for the possibility of a threshold dose response. The same dose response models as used in the original papers were fit to the data. The estimated cancer incidence from the fitted models over-predicted the observed cancer incidence in the lowest exposure group. This is consistent with a threshold or nonlinear dose-response at low-doses. Thresholds were added to the dose-response models and the range of possible thresholds is shown for both solid tumor cancers as well as the different leukemia types. This analysis suggests that the A-bomb cancer incidence data agree more with a threshold or non-linear dose-response model than a purely linear model although the linear model is statistically equivalent. This observation is not found with the mortality data. For both the incidence data and the mortality data the addition of a threshold term significantly improves the fit to the linear or linear-quadratic dose response for both total leukemias and also for the leukemia subtypes of ALL, AML, and CML. [ABSTRACT FROM AUTHOR]

The Linear No-Threshold (LNT) model has been traditionally used in the field of radiation safety. Public attention to and debate on this model increased after estimates that current Computed Tomography (CT) procedures in the USA will ultimately be responsible for up to 2% of cancers. However, there is evidence that in the mGy range, low doses not only cause a relatively low probability of deoxyribonucleic acid (DNA) damage, but may also involve adaptive protection against DNA damage. Thus, we have to realise that the dose-response relationship cannot be based on a simple mathematical equation of the first order. The LNT model should be rejected. [ABSTRACT FROM AUTHOR]