"Low Level
Radiation Health Effects: Compiling  the Data"

Revision 2
March 19, 1999

by Radiation, Science, and Health, Inc.,
Edited by J. Muckerheide

1.3
Animal & Plant
Biology

1.3.1
Mammals

References

"In animals and humans low-level radiation presumably leads to an increase in life span. This increased longevity has been attributed to two factors: (1) an initial production of free radicals (which are thought to be involved in aging (Harman 1986)) as a result of low-level radiation leading to a feedback reduction of intracellular free radical levels; (2) the fact that these phenomena resemble caloric intake restriction effects (Totter 1987) (caloric intake restriction has been found to increase life span (Totter 1985)). Low-level radiation is known to produce oxygen radicals, which affect endocrine balance. This is interpreted by the body as an increased food intake, thus lowering appetite and therefore caloric intake, which in turn increases longevity."

"Animal experiments. Theories on hormesis have been tested by performing experiments on mammals. Congdon (1987) reviewed some of these with interesting results. Starting in the 1940s, experiments at the National Cancer Institute (USA) led by Lorenz exposed mice, guinea pigs and rabbits to varying degrees of radiation. A group of mice was exposed to 0.11 R per 8-h day until natural death. The experimental group had a longer mean survival rate (nearly 2 months compared to the control group). There was also an increased body weight in the irradiated animals: animals exposed to 0.11 R had an average weight increase of 50% over the controls after approximately 69 weeks of exposure."