Weight-of-evidence environmental risk assessment

In this chapter, the data generated within MODUM and other related projects, i.e. CHEMSEA, MERCW and NordStream, contributing to the knowledge and data on occurrence, toxicity and effects of chemical warfare agents (CWAs) and their metabolites in the Baltic Sea, are aggregated. The data are evaluated and assessed in terms of risk quotients, and whether these point to risk or no-risk towards effects on lower tier organisms (e.g. algae and daphnia), and higher tier organisms (fish) from exposure to dumped CWAs and their metabolites in the study areas. To perform a semi-quantitative assessment of the environmental risk, a number of Lines of Evidences (LoEs) are set up, that take all aspects of the performed investigations into account. Each LoE is assigned +3, +2, +1, 0, -1, -2 or -3, indicating if the LoE is found to be for (+), against (-) or neutral (0) to an increased environmental risk of dumped CWAs. The weight also reflects the predictive power, or significance, of the individual LoEs. From nine LoEs a resulting summed score of +9 indicates that there is a weak to moderate potential for confirming the hypothesis. In order to qualify and increase the precision of the weights recommendations are given that can be addressed in future investigations regarding compounds, sites and species that could be in focus. Furthermore, recommendations for activities that will improve the exposure and toxicity data, that are inherent in the environmental risk assessment, are stated.