Wageningen Marine Research is involved in the development of methods and standards for Environmental Risk Assessment (ERA) which are currently used for regulatory and scientific purposes.
Environmental Risk Assessment (ERA) has become a generally used tool in the evaluation of the potential environmental impact of chemical products or activities. Since the late eighties, Wageningen Marine Research is active in environmental risk assessment. As such, we are and have been involved in the development of methods and standards which are currently used for regulatory and scientific purposes.
Our application of risk assessment models nearly always follows a tiered approach in order to balance required detail and effort.
PEC: PNEC risk screening based on worst-case assumptions on sensitivity and exposure.
The PEC:PNEC (assessment factor) approach is a generic conservative approach assuming the presence of the most sensitive species. To derive a PNEC using the assessment factor approach, preferably, toxicity data on at least the three selected taxonomic or trophic levels (e.g., algae, crustaceans, and fish) are available. In principle, the PNEC is determined from the available toxicity data, by applying an assessment factor. The PNEC is calculated by dividing the lowest LC/EC50 or NOEC value by an appropriate assessment factor in accordance with the EU-TGD. The assessment factor is applied to extrapolate from laboratory single-species toxicity test data to multi-species ecosystem effects. The assessment factor addresses a number of uncertainties:
- Interspecies variation (biological variance);
- Short-term to long-term toxicity extrapolation;
- Laboratory data to field impact extrapolation.
Probabilistic risk assessment; this approach uses the same type of input data as used in the PEC:PNEC approach but results in a more quantified risk estimate (probability that a species is exposed above its chronic NOEC).
This method preferably compares a frequency distribution of all possible exposure intensities with a threshold using the variation in species sensitivity. If a large data set with sensitivity values (L(E)C50s or NOECs) for different taxonomic groups is available, these values can be used to draw a distribution. This distribution that describes the variability of hazard of a stressor to organisms is called a Species Sensitivity Distribution (SSD). This distribution can be presented as a frequency distribution (cumulative normal distribution curves or other similar distribution curves) of NOEC values for species. In general the method works as follows: sensitivity data are log transformed and fitted to a distribution function. It has been shown that the choice of a distribution is quite arbitrary and is mostly done based on best fit results.
Biology based risk assessment uses the state of the art knowledge on biology, ecology, and toxicology and integrates principles to estimate effects on key species (individuals and populations), food chains, and ecosystems
It is obvious that the higher the tier of the risk assessment, the more specific the information needed on species, systems and toxic properties. Hence, there must be a justification for such a tiered approach that can be found in the area or of the stressor of concern. The higher the tier in risk assessment, the more comparable the results are to the results of monitoring; quantifying severity and extent of biological effects.
Wageningen Marine Research is very active in the further development of environmental risk assessment methods to suit the needs of the future. Our developments include:
- Cumulative Effects Assessment. The relevance of cumulative effects is recognized world wide. Despite all efforts, however, a common understanding of cumulative effects assessment is still lacking. Wageningen Marine Research is engaged in several studies to increase the understanding of this complex issue.
- Integrated environmental risk assessment consists of an combined evaluation of environmental impact on the basis of both risk assessment modeling and environmental monitoring. We developed a framework (Figure) for development of both risk modeling and effect monitoring into a more realistic an sophisticated endpoint for impact assessment.
- Biomarkers in risk assessment is an actual challenge that we have taken up for development recently. The biomarker approach in environmental monitoring is getting increasingly more attention as it provides an early indication of potential damage to an organism. Using biomarkers in risk assessment methods may close the gap between modeling and monitoring.