Fish bioaccumulation and biomarkers in environmental risk assessment: a review

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

Bioaccumulation of organic micropollutants in different aquatic organisms. Sublethal toxic effects on fish

Bioaccumulation of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) was investigated in plankton, crustaceans, and fish from two relatively small Amsterdam lakes, with different levels of contamination. Ratios between contaminant concentrations in organisms and sediments ranged from 0.1 to 41.7. The accumulation of pollutants could not be explained as a simple partitioning between sediment, water, and organisms. Probably, both biomagnification (PCBs and OCPs) and biotransformation (PAHs) affect the bioaccumulation in aquatic organisms. These effects were more pronounced in organisms of the higher trophic levels of the aquatic food-chain. Mixed function oxygenase (MFO) activity of liver microsomal fractions was determined in three fish species (roach, ccl, and pike) and compared with those of similar fish taken from a less contaminated lake that served as a reference. Despite the low level of contaminants present in the two lakes, an induction of both cytochrome P-450 and ethoxy-resorufin-O-deothylase (EROD) activity was observed in all three fish species involved. Pentoxyresoufin-O-depentylase (PROD) activity was induced in pike and eel only. Both the 3-methylcholan-threne-type inducible isozymes (P-450IA) and the phenobarbital-type inducible isozymes (P-450IIB) seem to be induced in the fish. These findings suggest that MFO enzyme activity in fish liver may be a suitable and sensitive indicator for the presence of trace organics in the aquatic environment. Despite the enzyme induction, no significant liver enlargement was observed in the fish species investigated, which can be interpreted as the absence of some pathological changes

Development of a framework to derive effect-based trigger values to interpret CALUX data for drinking water quality

Bioassays are increasingly being implemented for water quality monitoring as targeted chemical analyses are not always sufficient for the detection of all emerging chemicals or transformation products. However, the interpretation of bioassay results remains challenging, in particular because a positive response does not necessarily indicate that there may be an increased risk. For this purpose, effect-based trigger (EBT) values have been introduced as thresholds above which action needs to be undertaken to determine the cause of the response. The goals of this study were to (i) evaluate various approaches used to determine EBT values and (ii) based on the findings, derive human health EBT values for Chemical Activated LUciferase gene eXpression (CALUX) in vitro bioassays used for routine monitoring of water quality in the Netherlands. Finally, (iii) an uncertainty analysis was carried out to determine the protective power of the derived EBT values and the chance that potentially harmful substances might not be detected. EBT values that can be implemented in routine monitoring could be determined for four of eight selected bioassays. These EBT were compared to bioassay results from routine water quality monitoring carried out in the Netherlands. Furthermore, a framework for the calculation and evaluation of derived EBT values for routine application to monitor drinking water and its sources is proposed.</p

RISK-BASED APPROACH IN THE REVISED EU DRINKING WATER LEGISLATION : OPPORTUNITIES FOR BIOANALYTICAL TOOLS

A plethora of in vitro bioassays is developed in the context of chemical risk assessment and clinical diagnostics to test effects on different biological processes. Such assays can also be implemented in effect-based monitoring (EBM) of (drinking) water quality in parallel to chemical analyses. EBM can provide insight in the risks for environmental and human health associated with exposure to (unknown) complex low-level mixtures of micropollutants, which fits in the risk-based approach that was recently introduced in the European Drinking Water Directive. Some challenges remain, in particular related to selection and interpretation of bioassays. For water quality assessment, carcinogenesis, adverse effects on reproduction and development, effects on xenobiotic metabolism, modulation of hormone systems, DNA reactivity and adaptive stress responses are considered as the most relevant toxicological endpoints. An evaluation procedure of the applicability and performance of in vitro bioassays for water quality monitoring based on existing information has been developed, which can be expanded with guidelines for experimental evaluations. Besides, a methodology for the interpretation of in vitro monitoring data is required, since the sensitivity of specific in vitro bioassays in combination with sample concentration may lead to responses of chemicals (far) below exposure concentrations that are relevant for human health effects. Different approaches are proposed to derive effect-based trigger values (EBTs), including EBTs based on 1) relative ecotoxicity potency, 2) health-based threshold values for chronic exposure in humans and kinetics of reference chemicals, and 3) read-across from (drinking) water guideline values. EBTs need to be chosen carefully in order to be sufficiently but not over-conservative to indicate potential health effects. Consensus on the crucial steps in the selection and interpretation of in vitro bioassay data will facilitate implementation, as well as legal embedding in the context of water quality monitoring of such assays in EBM strategies. This article is protected by copyright. All rights reserved