UMB 4: Predictive Risk Assessment of Multiple Stressors

Background

The potential environmental impact of multiple stressors is poorly understood, and there is a need to develop a usable and realistic framework for environmental risk assessment (ERA) of multiple stressors.

Objectives

1) Combine existing frameworks for ERA of chemical mixtures and ionizing radiation (ERICA tool) to obtain an initial framework for ERA of multiple stressors. 2) Use the developed framework to: a) identify the total predicted risk of multiple stressors in a real case scenario with exposure to metals, organics and naturally occurring radioactive materials (NORMs), b) form a basis for prioritization of stressors according to their individual toxic units (TU) and/or risk-contribution, c) identify the most sensitive taxa and d) identify uncertainty related to knowledge gaps.

Material and methods

The ERA of multiple stressors was performed in a two-tiered approach of 1) summation of the ratios between the predicted exposure concentration (PEC) and the predicted no effect concentration (PNECs) followed by 2) summation of species-group (taxa) specific toxic units (STU) and subsequent calculation of taxa-specific risk quotients.

Main results and conclusion

The highest STU was observed for crustaceans, followed by fish and then algae for the chosen exposure scenario. The metals were the main toxicity drivers for crustaceans, organics and metals were the main toxicity drivers in fish, and metals and NORMs were the main toxicity drivers in algae. There is still a need for further development of the concept, especially in light of uncertainties associated with the bioavailability of the measured stressors and other factors that can influence the uncertainty of the ERA. Further development of the approach regarding metal speciation and efficiency improvement of effect-data compilation is currently ongoing.

Project Manager: Karina Petersen