Radiation Hormesis: an Evolutionary Expectation Invalidating the Linear No-threshold (lnt) Premise

Organisms survive best, or show high fitness, in the habitats in which they most commonly occur, a phenomenon referred to as hormesis in the literature of toxicology. Examples of hormesis accumulate rapidly in the literature. However, a lack of underlying models has led many to doubt its existence, especially for ionizing radiation. The evolutionary model developed here indicates that all potentially stressful environmental agents should show hormesis, so that the linear-no-threshold (LNT) premise should be invalid for all environmental agents including ionizing radiation. Furthermore, this evolutionary model incorporates aging towards environmental extremes. Contributions from 1989 include: (1.) Acetaldehyde utilization in Drosophila : an example of hormesis. Biol. J. Linnean Soc. 37: 183189, 1989. Acetaldehyde is an essential metabolite at low concentrations and becomes a stress at high concentrations; this hormetic relationship is illustrated by fitness measured by longevity. Organic metabolites such as acetaldehyde and organisms such as Drosophila provide models for genetical and molecular studies of hormesis. This approach assists in our understanding of suggestions over many years of enhanced fitness at natural background levels of ionizing radiation. (2.) Radiation hormesis: an evolutionary expectation and the evidence. Appl. Radiat. Isot. 41: 857860, 1990. Since there is a tendency for organisms to become progressively adapted to those environments to which they are most frequently exposed, radiation hormesis is an evolutionary expectation. (3.) Evolutionary adaptation and stress: the fitness gradient. Evolutionary Biology 26: 191-223, 1992. Impacts of environmental stresses are discussed in terms of fitness-stress continua which are necessarily non-linear. The evolutionary expectation of radiation hormesis is thereby put into an ecological context. (4.) Radiation hormesis: an evolutionary expectation based upon exposure to background radiation. BELLE Newsletter 3: 9-11, 1994.