Modelling ecological and human exposure to POPs in Venice lagoon. Part I - Application of MERLIN-Expo tool for integrated exposure assessment
Résumé
Industrial and urban emissions over several decades left a legacy of contamination by persistent organic pollutants in the sediments of Venice lagoon (Italy), which might still represent a hazard for the health of ecosystems and population. A new modelling tool for integrated exposure assessment, MERLIN-Expo, was applied to simulate integrated ecological and human exposure to PCBs and dioxins. MERLIN-Expo library provides a set of environmental fate models that can be easily combined to create several scenarios, and coupled to a human intake and a physiologically-based pharmaco-kinetic (PBPK) model to simulate human internal exposure. The Phytoplankton, Invertebrate and Fish models implemented in MERLIN-Expo library were combined to create an aquatic food web and to dynamically simulate bioaccumulation and biomagnification of dioxins and PCBs. Concentrations of PCB and dioxins in water, reconstructed from concentrations in dated sediment cores, were used as time-series inputs to run long term simulations. Estimated concentrations in edible aquatic species were used to estimate daily human intake through the consumption of local seafood. Finally, the application of the PBPK model allowed to explore the accumulation of 2,3,7,8-TCDD and PCB126 in human tissues for several decades. Simulated chemical concentrations in biota were evaluated against monitoring data for four aquatic species, finding an appreciable agreement, with some differences depending on the species and target chemicals. Estimated chemical concentrations in blood were compared to real human biomonitoring data measured in adult men. Despite several assumptions included in the assessment framework, simulated concentrations resulted close to measured data (the same order of magnitude or one order of difference). The results allowed performing a preliminary ecological and human health risk assessment for the selected chemicals by evaluating the exposure estimates against benchmark values available in literature. The study provided useful insights for supporting the verification of MERLIN-Expo in a real complex exposure scenario.