SREL Reprint #2890

A case against biomarkers as they are currently used in radioecological risk analyses: A problem of linkage

T. G. Hinton1 and F. Bréchignac2

1University of Georgia, Savannah River Ecology Laboratory, Aiken South Carolina, USA
2Institute of Radioprotection and Nuclear Safety (IRSN), Centre of Cadarache, France

Abstract: Biomarkers are successfully used in human risk analyses as early indicators of contaminant exposure and predictors of deleterious effects. This has boosted the search for biomarkers in determining ecological risks to non-human biota, and particularly for assessments related to radioactive contaminants. There are difficulties, however, that prevent an easy transfer of the biomarker concept from humans to non-human biota, as there are significant differences in endpoints of concern, units of observation and dose response relationships between human and ecological risk analyses. The use of biomarkers in ecological risk analyses currently lacks a linkage between molecular-level effects and quantifiable impacts observed in individuals and populations. This is important because ecological risk analyses generally target the population level of biological organisation. We highlight various examples that demonstrate the difficulties of linking individual responses to population-level impacts, such as indirect effects and compensatory interactions. Ecotoxicologists cope with such difficulties through the use of uncertainty or extrapolation factors. Extrapolation factors (EF) typically range from 1 to 1000 when linking effects observed in individuals to those predicted to occur in populations. We question what magnitude of EF will be required when going from a molecular level effect, measured by a biomarker, all the way up to the population level of biological organisation. Particularly, we stress that a successful application of biomarkers to radioecological risk assessment can only be achieved once the connection has been made between changes in individual resource allocation-based life histories and population dynamics. This clearly emphasises the need to quantify the propagation of molecular and cellular level effects to higher levels of biological organisation, especially in the long-term via several generations of exposure. Finally, we identify pertinent research approaches that are more system-oriented, and thus may help solve the problem of linking effects across levels of biological organisation.

SREL Reprint #2890

Hinton, T. G. and F. Bréchignac. 2005. A case against biomarkers as they are currently used in radioecological risk analyses: A problem of linkage. pp. 123-135 In F. Bréchignac and B. J. Howard (Eds.). Scientific Trends in Radiological Protection of the Environment. IRSN, France.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).