Setting sediment guidelines for chemicals that bioaccumulate can be problematic. Guidance for deriving such guidelines encourages the use of sediment toxicity tests which are usually invertebrates or the use of field data where effects are allocated equally to all contaminants present in the sediments.
For chemicals that bioaccumulate, such procedures do not necessarily incorporate the accumulation of the chemical (or group of chemicals) as toxicity tests are usually fairly short term or test or field data may not provide information for the right types of organisms.
This issue is particularly clear when considering how to derive sediment guidelines for dioxin-like compounds. Sediment ecotoxicity data are almost non-existent for this group. Field data looking at sediments in industrial harbours predominantly address effects in invertebrates which are not the most sensitive organisms for this chemical group. Work to understand the ecotoxicity of this group of chemicals for aquatic organisms has identified that it is accumulation of the compounds that is critical (i.e. tissue residues) and the most sensitive organism type is fish – particularly the early life stages.
This project has reviewed the available literature and guidance in relation to setting sediment guidelines (in general), the ecotoxicity of dioxin-like compounds, the determination and use of biota-sediment accumulation factors and existing sediment guidelines for this group of chemicals. This presentation will discuss the process and provide a sediment guideline for dioxin-like compounds.