In this review, a wide array of bioaccumulation markers and biomarkers, used to demonstrate
exposure to and effects of environmental contaminants, has been discussed in relation
to their feasibility in environmental risk assessment (ERA). Fish bioaccumulation
markers may be applied in order to elucidate the aquatic behavior of environmental
contaminants, as bioconcentrators to identify certain substances with low water levels
and to assess exposure of aquatic organisms. Since it is virtually impossible to predict
the fate of xenobiotic substances with simple partitioning models, the complexity
of bioaccumulation should be considered, including toxicokinetics, metabolism, biota-sediment
accumulation factors (BSAFs), organ-specific bioaccumulation and bound residues. Since
it remains hard to accurately predict bioaccumulation in fish, even with highly sophisticated
models, analyses of tissue levels are required. The most promising fish bioaccumulation
markers are body burdens of persistent organic pollutants, like PCBs and DDTs. Since
PCDD and PCDF levels in fish tissues are very low as compared with the sediment levels,
their value as bioaccumulation markers remains questionable. Easily biodegradable
compounds, such as PAHs and chlorinated phenols, do not tend to accumulate in fish
tissues in quantities that reflect the exposure. Semipermeable membrane devices (SPMDs)
have been successfully used to mimic bioaccumulation of hydrophobic organic substances
in aquatic organisms. In order to assess exposure to or effects of environmental pollutants
on aquatic ecosystems, the following suite of fish biomarkers may be examined: biotransformation
enzymes (phase I and II), oxidative stress parameters, biotransformation products,
stress proteins, metallothioneins (MTs), MXR proteins, hematological parameters, immunological
parameters, reproductive and endocrine parameters, genotoxic parameters, neuromuscular
parameters, physiological, histological and morphological parameters. All fish biomarkers
are evaluated for their potential use in ERA programs, based upon six criteria that
have been proposed in the present paper. This evaluation demonstrates that phase I
enzymes (e.g. hepatic EROD and CYP1A), biotransformation products (e.g. biliary PAH
metabolites), reproductive parameters (e.g. plasma VTG) and genotoxic parameters (e.g.
hepatic DNA adducts) are currently the most valuable fish biomarkers for ERA. The
use of biomonitoring methods in the control strategies for chemical pollution has
several advantages over chemical monitoring. Many of the biological measurements form
the only way of integrating effects on a large number of individual and interactive
processes in aquatic organisms. Moreover, biological and biochemical effects may link
the bioavailability of the compounds of interest with their concentration at target
organs and intrinsic toxicity. The limitations of biomonitoring, such as confounding
factors that are not related to pollution, should be carefully considered when interpreting
biomarker data. Based upon this overview there is little doubt that measurements of
bioaccumulation and biomarker responses in fish from contaminated sites offer great
promises for providing information that can contribute to environmental monitoring
programs designed for various aspects of ERA.