A tiered assessment framework to evaluate human health risk of contaminated sediment.

For sediment contaminated with bioaccumulative pollutants (e.g., PCBs and organochorine pesticides), human consumption of seafood that contain bioaccumulated sediment-derived contaminants is a well-established exposure pathway. Historically, regulation and management of this bioaccumulation pathway has focused on site-specific risk assessment. The state of California (United States) is supporting the development of a consistent and quantitative sediment assessment framework to aid in interpreting a narrative objective to protect human health. The conceptual basis of this framework focuses on 2 key questions: 1) do observed pollutant concentrations in seafood from a given site pose unacceptable health risks to human consumers? and 2) is sediment contamination at a site a significant contributor to seafood contamination? The first question is evaluated by interpreting seafood tissue concentrations at the site, based on health risk calculations. The second question is evaluated by interpreting site-specific sediment chemistry data using a food web bioaccumulation model. The assessment framework includes 3 tiers (screening assessment, site assessment, and refined site assessment), which enables the assessment to match variations in data availability, site complexity, and study objectives. The second and third tiers use a stochastic simulation approach, incorporating information on variability and uncertainty of key parameters, such as seafood contaminant concentration and consumption rate by humans. The framework incorporates site-specific values for sensitive parameters and statewide values for difficult to obtain or less sensitive parameters. The proposed approach advances risk assessment policy by incorporating local data into a consistent region-wide problem formulation, applying best available science in a streamlined fashion.

An integrated approach for bioaccumulation assessment in mussels: towards the development of Environmental Quality Standards for biota.

The possible use of chemical concentrations measured in mussels (Mytillus galloprovincialis) for compliance checking against Environmental Quality Standards (EQS) established for biota is analyzed with the help of an integrated model. The model consists of a 3D planktonic module that provides biomasses in the different compartments, i.e., phytoplankton, zooplankton and bacteria; a 3D fate module that provides the concentrations of contaminants in the water column and in the sediments; and a 3D bioaccumulation module that calculates internal concentrations in relevant biotic compartments. These modules feed a 0D growth and bioaccumulation module for mussels, based on the Dynamic Energy Budget (DEB) approach. The integrated model has been applied to study the bioaccumulation of persistent organic pollutants (POPs) in the Thau lagoon (France). The model correctly predicts the concentrations of polychlorinated biphenyls (PCBs) and polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) in mussels as a function of the concentrations in the water column and in phytoplankton. It also sheds light on the origin of the complexity associated with the use of EQS for biota and their conversion to water column concentrations. The integrated model is potentially useful for regulatory purposes, for example in the context of the European Water Framework (WFD) and Marine Strategy Framework Directives (MSFD).