A
case against biomarkers as they are currently used in radioecological
risk analyses: A problem of linkage.
T.
G. Hinton1 and F. Bréchignac2
Author Affiliations
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. p. 123-135. In Scientific Trends in Radiological Protection of the Environment, edited by F. Bréchignac and B.J. Howard. IRSN, France.
