Conclusions: Biomarkers in Environmental Risk Assessment - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 412

In the United States, the federal Toxic Substances Control Act gives the Environmental
Protection Agency (USEPA) the authority to regulate, and even ban, the manufacture, use,
and distribution of both new and existing chemicals. In Europe, significant improvement
has occurred recently with the adoption of a new chemical policy, REACH (Registration,
Evaluation, and Authorization of CHemicals).
16.1 How Can We Assess Environmental Quality?
Environmental assessment is classically based on a triad of analyses including (1) chemical
analyses in environmental matrices; (2) bioassay methods for the evaluation of toxic effects
of contaminants typically in the laboratory; (3) biological responses in the field at the level
of community structure. This approach was particularly well developed as the Sediment
Quality Triad (Chapman 1990) since, in the aquatic environment, this compartment is the
main store for most of the contaminants entering ecosystems. It is extremely difficult to
establish a cause-effect relationship when effects result from exposure to mixtures, a situ-
ation, however, which is that most commonly encountered in the field.
16.1.1 Chemical Monitoring
The pros and cons of measurements of chemicals in environmental matrices (water, sed-
iment, biota) have been recently reviewed (Amiard-Triquet and Rainbow 2009; Knoery
and Claisse 2010). Chemical analyses mainly provide information on chemicals that are
perceived to be relatively easy to analyze such as trace metals, DDT and its metabolites,
γHCH, αHCH, some congeners of polychlorinated biphenyls (PCBs), and some individual
polycyclic aromatic hydrocarbons (PAHs). Among the roughly 100,000 chemicals that have
at least limited toxicity information available, only 1150 unique compounds are measured
in waters (Egeghy et al. 2012). However, complex mixtures are present in certain environ-
ments (such as major estuaries across the world), including many classes of compounds
(many persistent organic pollutants and emerging contaminants such as pharmaceuticals
and nanoparticles) that are not yet accessible to analysis or are extremely expensive to
analyze. Moreover, the physicochemical parameters of the medium interfere with con-
taminants, thus modifying their characteristics and their bioavailability (Figure 16.1).
Analyzing contaminants in biota rather than in water or sediment gives access to the bio-
available fraction of the pollutant load in the medium that is the component that has the
potential to induce toxic effects.
16.1.2 Bioindicator Indices
One of the main objectives of aquatic ecotoxicological research is the assessment of contami-
nant impacts on populations, communities, and ecosystems in support of legislation that has
been adopted on a worldwide scale to determine the ecological integrity of surface waters
[United States' Clean Water Act, 1972; European Community Water Framework Directive
(WFD), 2000]. Many bioindicator indices (at the level of populations and communities, see
Chapter 7) have been proposed, but it is difficult to attribute effects at these high levels of
biological organization to the presence of contaminants rather than to other stress factors
(e.g., habitat alteration, overfishing), particularly in highly dynamic and complex systems