Anders Møller and timothy Mousseau are a research team routinely looking at the impact of radiation from both chernobyl and Fukushima on plants and animals (see radiation Shorts in this issue for further coverage). their considerable and growing body of work has turned up questions about variability in radiation impact on different species. this year, in part to provide baseline information on this issue of variability, the two turned their considerable quantitative skills to the question of whether 1000-fold differences in ambient levels of radiation around our planet, due to differences in elements in the soil and rocks at these locations have impacted evolutionary processes in plants and animals. In addition, the two squarely ask: if there is any impact, is it harmful or beneficial?
"The flipside of negative fitness consequences is evolutionary adaptation to radiation...Here we suggest that the documented consequences of naturally increased levels of background radiation have important implications for hormesis. In particular, we would expect that radiation hormetic effects should be found in areas with higher levels of natural background radiation because of adaptation to such enhanced levels of radiation, and we predict that on average radiation should have positive effects on the wellbeing of humans and other organisms if hormesis operates at naturally occurring low-dose radiation."
Since industry-paid experts persist in bringing forward hormesis (the notion that some radiation exposure can be good for you), this study provides a powerful reply not from cells in a dish in a laboratory, but from nature, and over the timescale where one would expect to be able to measure the benefits if they are there--evolutionary time.
Variations in natural background radiation result from variation in radioactivity in Earth's rocks and soils, either due to geological processes or, and in some cases, large extraterrestrial impacts. In this study the authors are explicitly not looking at sites with radioactivity from atomic military or industrial activity.
"The effects of natural variation in background radioactivity on humans, animals and other organisms"published in November 2012, is a "meta-analysis" in which Møller and Mousseau identified about 5000 previously published papers on this subject, and from these selected 46 to apply statistical analysis. Spanning multiple continents, many species and a variety of focal points of research, the two conclude that natural low-level radioactivity is damaging, even in the long time frames in which adaptation is possible. This finding is important since contamination from human atomic activities (nearly all within the 20th and 21st centuries) has not had sufficient time to produce the long-term consequences that radiation-induced selection on the study sites, where evolutionary time frame has passed.
"...this review attempts to provide baseline information concerning the potential consequences of nuclear accidents like those at Chernobyl and Fukushima."
Møller and Mousseau expressly looked for, but did not find, positive effects from radiation in 46 studies that looked at a control population and a population exposed to elevated radiation where the levels of radiation were monitored in both groups. The studies varied in focal point but included including findings on rates of mutation, DNA repair, physiology, morphology, disease rates, shifts in immunological function, sex ratio and fecundity in human beings, other animals, plants and fungi. The statistical analysis made possible from aggregating the populations across 46 studies is very powerful and enabled very clear findings that were not due to "random chance" (i.e. statistically significant) in every dimension examined, and those findings are that radiation causes harm, even at very low levels, and even over very long periods of time when any adaptation that was going to happen would have happened.
Because claims of hormesis from industry employed experts are again becoming a drumbeat, we offer this lengthy excerpt from Møller and Mousseau:
“Hormesis is defined as a beneficial effect of normal background radiation on life-history traits such as fecundity and longevity compared to levels achieved in the complete absence of radiation (reviews in Kondo, 1993; Luckey, 1991). If hormetic effects of radiation on fitness exist, we should expect that the optimal level of radiation should increase with background radiation level. If hormesis has evolved as a consequence of local adaptation to specific levels of radiation, we might even find that all populations should perform best at some local level of radiation; exceeding their performance in the absence of radiation. The latter scenario would suggest that fitness should be independent of level of natural background radiation. In either case we should not expect to find increased mutation rates, impaired immune function, increased incidence of disease and increased mortality in areas with higher levels of normal background radiation. Our findings are clearly inconsistent with a general role for hormesis in adaptation to elevated levels of natural background radiation.”
Indeed, across the 46 studies included, the authors found elevated rates of deleterious mutation, aberrant morphology, and disease (including cancer in humans) resulting from multiple measurable impacts of radiation, including impaired immuno-function and reduced rates of DNA repair. The pair chose to exclude radon exposure, explaining that there is a large literature that could dilute the studies of other types of exposure, and radon studies are reviewed elsewhere. Interestingly, the authors do note cases of radiation resistance--reduced rates of damage--which is differentiated from hormesis. The theory of hormesis is that radiation confers benefit. The discussion of resistance to radiation focuses on lower animal/bacteria and likely increased resistance to oxidation. Plants, where one might assume to see greater adaptation, actually show the highest level of harm from growing in more radioactive soils. The authors do note, however, that "there is no evidence of radio-tolerance or radioresistance in humans."
Paper reviewed here:
Anders P. Møller, Timothy A. Mousseau. the effects of natural variation in background radioactivity on humans, animals and other organisms. Biological Reviews,2012 http://cricket.biol.sc.edu/chernobyl/papers/MollerMousseau-BRV-2012.pdf
Other reporting on this study:
Science Daily reports University of South Carolina. "Even lowlevel radioactivity is damaging, scientists conclude."ScienceDaily,13 Nov. 2012. Web. 2 Dec. 2012. http://www.sciencedaily.com/releases/2012/11/121113134224.htm
Archive of the studies underlying this paper: http://cricket.biol.sc.edu/papers/natural/
Archive of Møller and Mousseau (et al) papers on Chernobyl: http://cricket.biol.sc.edu/chernobyl/Chernobyl_Research_Initiative/Publi...
Initial study of Fukushima by Møller and Mousseau http://cricket.biol.sc.edu/chernobyl/Chernobyl_Research_Initiative/Fukus...