The risk assessment of substances to the marine environment is linked with uncertainty due to several reasons, e.g. the marine environment encompasses a higher biodiversity than the freshwater environment. Moreover, the number of toxicity data on marine organisms for the marine effect assessment is in comparison to freshwater toxicity data limited.
The marine risk assessment is implemented as part of the ecological risk assessment for chemicals in the
framework of EU regulation (EU Technical Guidance Document (TGD) on Risk Assessment 2003). For those substances for which marine toxicity data are not available, freshwater data are applied as substitutes by considering a safety factor for the extrapolation to marine organisms according to the TGD. The aim of the study
was to answer the question whether the current database on marine toxicity supports this procedure to predict the sensitivity of marine organisms to narcotics. As the toxicity of narcotic substances is based on the disturbance of the integrity and functioning of cell membranes, and thus possesses an unspecific mode of action, the hypothesis was scrutinised that there is no significant difference in the relative toxicity of freshwater and saltwater organism to narcotics. If the hypothesis is valid, freshwater toxicity data could be used to predict the sensitivity of marine organisms towards narcotics.
In order to evaluate this hypothesis, the Cefic marine toxicity database was enlarged with marine and freshwater data of 64 selected non-polar (MoA 1) and polar (MoA 2) narcotics from other publicly accessible databases. As a result, a total of 2652 marine toxicity data points was available for this study. The linear regression analysis of
saltwater sensitivity from freshwater sensitivity showed for all substances and all taxa pooled that saltwater and freshwater toxicity data were significantly correlated.
However, the regression analysis of MoA 1 substances separated in the taxonomic groups revealed that there were significant differences between the freshwater and the saltwater sensitivity. While there was no significant difference between the freshwater and saltwater sensitivity of crustaceans, the sensitivity of saltwater fish to MoA 1 substances was higher than for freshwater fish. And the marine algae were significantly more sensitive than the freshwater algae. This is of high importance, as the algae test is a chronic test. The results were confirmed when considering priority substances only. Hence, the hypothesis that due to the unspecific mode of action of narcotics there is no difference in the sensitivity of freshwater and marine organism has to be rejected on the level of the taxonomic groups.
In conclusion, marine organisms can be significantly more sensitive to narcotics when the analysis is conducted on the taxonomic level of phyla. The reflection on the level of phyla is essential for the marine environment, as it encompasses a higher biodiversity than the freshwater environment with 16 exclusively marine phyla. In the current toxicity and CBB databases, data on important marine phyla, like molluscs, and exclusively marine phyla, e.g., on echinodermata, urochordata or tunicata are urgently missing. As biodiversity is of high importance for ecosystem structure and functioning the sensitivity of species which represent phyla underrepresented so far and linked with different exposure routes e.g. via different food uptake, like filter feeders, should be considered in the future.
Based on the analysis of the currently available data, taking the uncertainty in the extrapolation of the sensitivity of marine organisms to narcotics into account by applying a safety factor of 10 can be seen as an appropriate but preliminary approach. Additional investigations are necessary to further reduce the risk for key marine taxonomic groups, and to finally be able to provide robust safety factors.
C Floeter, W Ahlf, HEC von Lochow, AR Temara, M Holt, HT Ratte, Assessing the uncertainty in the extrapolation of the sensitivity of freshwater to saltwater organisms exposed to narcotics, submitted.