The Lesser Evil: Plutonium-239 or Uranium-235? A Study on F0 Atomic Bomb Survivors

Abstract

‘All models are wrong, but some models are useful.’ Radioactivity is a life-detrimental exposure that increases individuals’ susceptibility to cancer onset. The plasticity of the aging rate, expressed as d(log μ(x))/dx, has been informally acknowledged, often conflated with mortality rate μ(x) or risk log μ(x). A formal examination of this plasticity is lacking. The mortality schedule of irradiated F0 atomic bomb survivors in Hiroshima (U-235) and Nagasaki (Pu-239) at age exposure 40 - 45 (ATE45) can unveil the characteristics of hazard trajectories by isotope type and dosimetry. Based on the advantage derived from background radiation, an alternative population was employed during the comparative study. A dose-dependent relationship between radioactive isotope types and the rate of aging was presented in the frailty framework; _γ-Gompertz-Makeham_. Among survivors within the 0-5mGy range, an apparent pseudo-benefit initial mortality risk, linked to the distance from the epicenter, implies that mortality selection is influenced by both impact severity and natural frailty. Moreover, the standardized mortality ratio indicates a more pronounced impact of Pu-239 on age-specific mortality trajectories compared to U-235. In the 0-5mGy range, Pu-239 shows 11% (M) and 37% (F), while U-235 exhibits 4% (M) and 0.5% (F). Upon intense radiation exposure, variation in the human rate of aging exists within a 10-km radius from the epicenter, and gender sensitivity may be a significant contributor to mortality selection.