Nuclear bomb and public health

Since the nuclear bomb attack against Hiroshima and Nagasaki in 1945, the world has advanced in nuclear technology. Today, a nuclear bomb could target a large-scale attack, at a longer range, and with much greater destructive force. People are increasingly concerned about the potential destructive humanitarian outcomes. We discuss actual conditions detonation of an atomic bomb would create, radiation injuries, and diseases. We also address concerns about functionality of medical care systems and other systems that support medical systems (i.e., transport, energy, supply chain, etc. systems) following a massive nuclear attack and whether citizens able to survive this.

Fetal atomic bomb survivor dosimetry using the J45 series of pregnant female phantoms with realistic survivor exposure scenarios: comparisons to dose estimates in the DS02 system

A significant source of information on radiation-induced biological effects following in-utero irradiation stems from studies of atomic bomb survivors who were pregnant at the time of exposure in Hiroshima, and to a lesser extent, from survivors in Nagasaki. Dose estimates to the developing fetus for these survivors have been assigned in prior dosimetry systems of the Radiation Effects Research Foundation as the dose to the uterine wall within the non-pregnant adult stylized phantom, originally designed for the dosimetry system DS86 and then carried forward in DS02. In a prior study, a new J45 (Japanese 1945) series of high-resolution phantoms of the adult pregnant female at 8 weeks, 15 weeks, 25 weeks, and 38-weeks post-conception was presented. Fetal and maternal organ doses were estimated by computationally exposing the pregnant female phantom series to DS02 free-in-air cumulative photon and neutron fluences at three distances from the hypocenter at both Hiroshima and Nagasaki under idealized frontal (AP) and isotropic (ISO) particle incidence. In this present study, this work was extended using realistic angular fluences (480 directions) from the DS02 system for seven radiation source terms, nine different radiation dose components, and five shielding conditions. In addition, to explore the effects of fetal position within the womb, four new phantoms were created and the same irradiation scenarios were performed. General findings are that the current DS02 fetal dose surrogate overestimates values of fetal organ dose seen in the J45 phantoms towards the cranial end of the fetus, especially in the later stages of pregnancy. For example, for in-open exposures at 1000 m in Hiroshima, the ratio of J45 fetal brain dose to DS02 uterine wall dose is 0.90, 0.82, and 0.70 at 15 weeks, 25 weeks, and 38-weeks, respectively, for total gamma exposures, and are 0.64, 0.44, and 0.37 at these same gestational ages for total neutron exposures. For organs in the abdominal and pelvic regions of the fetus, dose gradients across gestational age flatten and later reverse, so that DS02 fetal dosimetry begins to underestimate values of fetal organ dose as seen in the J45 phantoms. For example, for the same exposure scenario, the ratios of J45 fetal kidney dose to DS02 uterine wall dose are about 1.09 from 15 to 38 weeks for total gamma dose, and are 1.30, 1.56, and 1.75 at 15 weeks, 25 weeks, and 38 weeks, respectively, for the total neutron dose. Results using the new fetal positioning phantoms show this trend reversing for a head-up, breach fetal position. This work supports previous findings that the J45 pregnant female phantom series offers significant opportunities for gestational age-dependent assessment of fetal organ dose without the need to invoke the uterine wall as a fetal organ surrogate.

Intracellular reactive oxygen species level in blood cells of atomic bomb survivors is increased due to aging and radiation exposure

Although reactive oxygen species (ROS) play important roles in immune responses, excessive ROS production and accumulation might enhance the risk of inflammation-related diseases. Moreover, impaired immune function and the acceleration of pre-clinically persistent inflammation due to aging and radiation exposure have been observed in atomic bomb (A-bomb) survivors more than 60 years post-exposure. Meanwhile, the effects of aging and radiation exposure on ROS production in immune cells have not been characterized. This study investigated the relationship between intracellular ROS (H₂O₂ and O₂^•-) levels in blood cells or T cell subsets and serum iron, ferritin, and C-reactive protein (CRP) levels, as well as how these variables are affected by age and radiation exposure in A-bomb survivors. We examined 2495 Hiroshima A-bomb survivors. Multiple linear regression models adjusted for confounding factors indicated that intracellular O₂^•- levels in monocytes, granulocytes, and lymphocytes, and particularly in memory CD8⁺ T cells, including effector memory and terminally differentiated effector memory CD8⁺ T cells, increased with radiation dose. Additionally, serum iron, ferritin, and CRP levels affected intracellular ROS levels in specific blood cell types and T cell subsets. Serum CRP levels increased significantly with increasing age and radiation dose. Finally, when divided into three groups according to serum CRP levels, dose-dependent increases in the intracellular O₂^•- levels in blood cells and central memory and effector memory CD8⁺ T cells were most prominently observed in the high-CRP group. These results suggest that an increase in the levels of certain intracellular ROS, particularly after radiation exposure, might be linked to enhanced inflammatory status, including elevated serum CRP levels and reduced serum iron levels. This study reveals that aging and radiation exposure increase oxidative stress in blood cells, which is involved in impaired immune function and accelerated pre-clinically persistent inflammation in radiation-exposed individuals.

The Muller-Neel dispute and the fate of cancer risk assessment

The National Academy of Sciences (NAS) Atomic Bomb Casualty Commission (ABCC) human genetic study (i.e., The Neel and Schull, 1956a report) showed an absence of genetic damage in offspring of atomic bomb survivors in support of a threshold model, but was not considered for evaluation by the NAS Biological Effects of Atomic Radiation (BEAR) I Genetics Panel. The study therefore could not impact the Panel's decision to recommend the linear non-threshold (LNT) dose-response model for risk assessment. Summaries and transcripts of the Panel meetings failed to reveal an evaluation of this study, despite its human relevance and ready availability, relying instead on data from Drosophila and mice. This paper explores correspondence among and between BEAR Genetics Panel members, including James Néel, the study director, and other contemporaries to assess why the Panel failed to use these data and how the decision to recommend the LNT model affected future cancer risk assessment policies and practices. This failure of the Genetics Panel was due to: (1) a strongly unified belief in the LNT model among panel members and their refusal to acknowledge that a low dose of radiation could exhibit a threshold, a conclusion that the Néel/Schull atomicbomb study could support, and (2) an excessive degree of self-interest among panel members who experimented with animal models, such as Hermann J. Muller, and feared that human genetic studies would expose the limitations of extrapolating from animal (especially Drosophila) to human responses and would strongly shift research investments/academic grants from animal to human studies. Thus, the failure to consider the Néel/Schull atomic bomb study served both the purposes of preserving the LNT policy goal and ensuring the continued dominance of Muller and his similarly research-oriented colleagues.

Epidemiological studies of atomic bomb radiation at the Radiation Effects Research Foundation

Epidemiological studies of people who were exposed to atomic bomb radiation and their children who were conceived after parental exposure to radiation (F₁) have investigated late health effects of atomic bomb radiation and its transgenerational effects. Those studies were initiated by the Atomic Bomb Casualty Commission (ABCC) in the 1950s. ABCC was reorganized to the Radiation Effects Research Foundation (RERF) in 1975, which continued the work of the ABCC. Follow-up of vital status and cause of death is performed for all RERF cohorts, including the atomic bomb survivors (the Life Span Study: LSS), in utero survivors, and the children of the survivors (F₁). Cancer incidence is investigated for accessible subpopulations of the cohorts. Health examinations for subcohorts of the LSS and in utero survivors are conducted as the Adult Health Study (AHS); a program of health examinations for a subcohort of the F₁ study is called the F₁ Offspring Clinical Study (FOCS). Participants of all clinical programs are asked to donate their blood and urine for storage and future biomedical investigations. Epidemiological studies have observed increased radiation risks for malignant diseases among survivors including those exposed in utero, and possible risks for some noncancer diseases. No increased risks due to parental exposure to radiation have been observed for malignancies or other diseases in F₁, but continuing investigations are required.

Human genetics after the bomb: Archives, clinics, proving grounds and board rooms

In this paper I track the history of post-1945 human genetics and genomics emphasizing the importance of ideas about risk to the scientific study and medical management of human heredity. Drawing on my own scholarship as it is refracted through important new work by other scholars both junior and senior, I explore how radiation risk and then later disease risk mattered to the development of genetics and genomics, particularly in the United States. In this context I excavate one of the central ironies of post-war human genetics: while studies of DNA as the origin and cause of diseases have been lavishly supported by public institutions and private investment around the world, the day-to-day labor of intensive clinical innovation has played a far more important role in the actual human experience of genetic disease and genetic risk for affected families. This has implications for the archival record, where clinical interactions are less readily accessible to historians. This paper then suggests that modern genomics grew out of radiation risk; that it was and remains a risk assessment science; that it is temporally embedded as a form of both prediction and historical reconstruction; and that it has become a big business focused more on risk and prediction (which can be readily marketed) than on effective clinical intervention.

Impact of Nagasaki atomic bomb exposure on myelodysplastic syndrome patients who are treated with azacitidine

BACKGROUND/AIM

High-dose radiation exposure greatly increases the risk of myelodysplastic syndromes (MDS), however the clinical characteristics of MDS among atomic bomb survivors have not been thoroughly investigated to date. We designed this study to identify these characteristics.

PATIENTS AND METHODS

We retrospectively evaluated data from 13 atomic bomb survivors with MDS and 15 elderly patients with de novo MDS who were diagnosed between April 2011 and April 2013 at the Nagasaki Genbaku Hospital. All patients were treated with azacitidine (AZA; a hypomethylating agent) and overall survival rates were estimated.

RESULTS

No clear difference was observed in the clinical response to AZA between the two groups. However, atomic bomb survivors had a survival disadvantage, independent of their karyotype.

CONCLUSION

Minute genetic alterations caused by exposure to atomic radiation can adversely affect the response to AZA, even 66 years after the exposure. Further studies are required to clarify the mechanisms underlying this phenomenon.