Integration of environmental and human PBPK exposure models : application of MERLIN-Expo modelling tool to POPs exposure in Venice lagoon
Résumé
MERLIN-Expo is a new tool for integrated exposure assessment recently developed under the FP7 project “4FUN”. MERLIN-Expo incorporates advanced models simulating the fate of chemicals in the environment and in human body (PBPK model) into an easy-to-use tool. Models available in the MERLIN-Expo library are implemented on a common platform to facilitate integrated full-chain assessments for combined exposures. Models can be used to simulate fate of organic (PAHs, PCBs, dioxins) and inorganic contaminants. Software enables end-user to apply set of functionalities such as uncertainty and sensitivity analysis, dynamic deterministic and probabilistic simulations in order to address different exposure and chemical fate problems. MERLIN-Expo was applied to assess long term ecological and human exposure to PCBs and PCDDs in the Venice lagoon (Italy). Data from literature describing pollution historical trends in the lagoon, estimated in dated sediment cores, were used as time-dependent model input. In order to simulate bioaccumulation in specific aquatic food web three models were implemented in MERLIN-Expo library: Phytoplankton, Aquatic Invertebrate and Fish, allowing to represent specific organisms. Aquatic food web model was then coupled to PBPK model to simulate chemical concentration in aquatic organisms and in human serum after dietary exposure to contaminated seafood. Modelling results are then tested against available monitoring data on chemical concentrations in edible aquatic species and concentrations in serum of adult men in Venice area to assess the accuracy and applicability of the proposed tool to real complex scenarios. Full chain exposure assessment is then complemented by uncertainty and sensitivity analysis including local sensitivity methods, screening methods (e.g. Morris method), global regression methods (e.g. Standardised Regression Coefficients), and global variance based methods (e.g. FAST, EFAST, Sobol). These methods allow to follow for instance WHO (2008) recommendations to perform three stage uncertainty/sensitivity analysis, adopting qualitative, semi-qualitative, and quantitative methods. Integration of environmental and human exposure models in MERLIN-Expo allows comprehensive assessment of exposure and thus better characterisation of overall risk to human and environment especially in the case of higher tier assessment. Finally, MERLIN-Expo follows a Quality Assurance and Standardisation process for documentation in collaboration with CEN (European Committee for Standardisation). This makes the tool interesting and promising for potential applications in different regulatory domains.last decade has witnessed an increasing interest in assessing health risks caused by contaminants present in several environmental media, i.e. soil, air, and water. To that end, mathematical models describing the fate of compounds in the environment (multi-media models) and in the human body (toxicokinetic models) can be combined to simulate realistic exposure scenarios of the human populations. These models can also be integrated in a Geographic Information System (GIS) to produce maps of exposure and reveal spatial patterns. The aim of this study was to develop a spatial stochastic multimedia and human exposure model for detecting vulnerable populations and analyzing exposure determinants at a fine resolution and regional scale. This approach was applied to the exposure to lead of children in the Region Nord-Pas-de-Calais in France.