Metabolic efficiency in response to environmental agents predicts hormesis and invalidates the linear no-threshold...

Hormesis derives from high metabolic efficiency and hence high fitness that evolve in response to single and multiple environmental agents in low to moderate stress habitats. Consequently, nonlinear fitness continua are an evolutionary expectation for all environmental agents, which invalidates the LNT premise. For ionizing radiation, hormesis is interpreted to be adaptation to background radiation exposures, combined with adaptation to higher radiation exposures dependent on metabolic protection from the array of other abiotic stresses in the environment. This model of radiation hormesis renders suggestions of therapeutic radiation supplementation redundant because of similar health effects from other environmental agents. Furthermore, the model is compatible with a return of exposure levels for radiation protection to higher doses than are presently permissible, a deduction with substantial economic benefits.