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(T/MF145) The Development of a Multi-Media Exposure Assessment Approach for New Substances in Canada . Postlethwaite, Emma1, Bonnell, Mark 2, Atkinson, Andy1, Hammond, Greg 1, 1 2 ABSTRACT- Recently the New Substances Division (NSD) of Environment Canada undertook a qualitative examination of the uncertainties associated with the exposure assessment process used to estimate environmental concentrations of new substances in the Canadian environment. Traditionally, new substance exposure assessment has relied on a one compartment model (water column) to estimate a predicted environmental concentration (PEC). It was determined that one of the largest data gaps contributing to exposure uncertainty was the lack of consideration of exposures to biota inhabiting media other than the water column. In this regard, the NSD has initiated the development of a preliminary framework for the multi-media exposure assessment of new substances based on chemical partitioning. Releases of new substances to the environment are primarily industrial facility-based, but can occur on a house-hold basis (down the drain) and directly to the environment (e.g., fracturing fluids). Accordingly, the preliminary framework uses life-cycle information to estimate the main release points to the environment and then determines the exposure pathway(s) of concern by considering a substances partitioning behaviour both in waste water treatment plants and in the environment. Exposure compartments include soil (from the land-based application of biosludge), water column, sediment, food chain (terrestrial and aquatic), ground water and air. Individual models for estimating the concentration of new substances in sediment, soil, biota and air are currently being developed based on modifications of existing screening level approaches or using new techniques. The screening multi-media exposure assessment approach is intended to provide the NSD with a multi-compartment exposure model, but may also be used as a decision tool for requesting additional data (e.g., BCF test data) under the New Substance Notification Regulations to refine the ecological risk assessment. Key words: multi-media, exposure assessment, new substances, ecological risk assessment |
