History of Biomarkers - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 16

Although such chemical analyses are essential to identify concentration trends of con-
taminants (increase, plateau, or reduction) in the environment, they do not provide infor-
mation about the real impact of the pollutant on its final target—the living organism. It is
apparent then that this physicochemical assessment is insufficient to evaluate the health of
a complex medium, with a mixture of contaminants potentially leading to the phenomena
of synergy and antagonism. The concept of biological monitoring, based on the study of
the biological response of organisms to pollutants, termed biomarkers, is today well estab-
lished. The characterization of these biomarkers can constitute an early warning system
before the further deterioration of the structure and function of an organism, and particu-
larly before all the population or the ecosystem is disturbed. This concept is not new: it
is the principle of diagnosis in human medicine, founded on the detection of symptoms
likely to reveal a disease (Lafaurie et al. 1992).
2.2 Definition
In the past nearly 30 years, several definitions of biological markers have been published.
The historical development of the biomarker approach has been closely related to advances
in medicine and biology of vertebrates [National Research Council (NRC) 1987]. Biological
markers were classified as exposure, effect, and susceptibility biomarkers. Moreover, in the
publications of the NRC (1987, 1989), the authors highlighted that biological markers can be
simultaneously used for biological monitoring and for monitoring of health. According to
McCarthy and Shugart (1990), “biological markers are measurements at the molecular, bio-
chemical, or cellular level in either wild populations from contaminated habitats or in organ-
isms experimentally exposed to pollutants that indicate that the organism has been exposed
to toxic chemicals, and the magnitude of the organism's response to the contaminant.”
The definition was generalized by Depledge (1994): a biomarker is “a biochemical, cellu-
lar, physiological or behavioral change which can be measured in body tissues or fluids or
at the level of the whole organism that reveals the exposure at/or the effects of one or more
chemical pollutants.” In September 1994, the journal Ecotoxicology presented four reviews
on the role of the biomarkers in environmental assessment, as carried out with inverte-
brates (Depledge and Fossi 1994), vertebrates (Peakall and Walker 1994), terrestrial plants
(Ernst and Peterson 1994), and populations and communities of invertebrates (Lagadic et
al. 1994). These articles were required by the European Foundation for Science (ESF) to
understand to what extent biomarkers could be used to evaluate environmental damage
and to formulate possible rules to control any such damage.
Finally, Van Gestel and Van Brummelen (1996) attempted a redefinition of the terms
biomarkers, bioindicators, and ecological indicators, by calling on previous work pub-
lished in Ecotoxicology in 1994 when Lagadic et al. (1994) made a clear distinction between
biomarkers and bioindicators and restricted the use of the term “biomarker” to the sub-
lethal biochemical changes resulting from individual exposure to xenobiotics. However,
this reductionist definition was not generally accepted (Van der Oost et al. 2005; Allan
et al. 2006), with many scientists voicing their concern about not neglecting responses
(e.g., physiological, behavioral) that could be used in risk assessments involving a change
in scale of biological organization from the individual to the population. According to
Van Gestel and Van Brummelen (1996), a biomarker is defined as any biological response
to an environmental chemical contaminant at the infra-individual level, measured in an