Much of the discussion above makes clear that many potential pollutants have natural levels, harmless levels, or both, in sediment systems. As such, whilst the objective of the protection of the marine environment from pollution may be considered a risk-based objective, the protection from “sources of pollution”, and the objective of eliminating pollution, appear much more absolute. Many DM frameworks use SQGs that are background-based for their LALs. This allows them to focus BIRB 796 on the objective of elimination of pollution, in an absolute sense. However, many tiered decision frameworks are specifically designed to evaluate lines of evidence to determine whether constituents

present in a sediment pose a risk, and allow for both background-based

evaluation (to compare contaminant levels with regional selleck chemicals background conditions) but also bioavailability-based evaluation, to determine if constituents in place, whether natural or anthropogenic, pose a risk to human health and the environment. In these cases, SQGs selected for use are generally risk-based rather than background-based. The selection of the level and basis of SQGs, and how they are used within the decision framework, are critical factors in how a decision framework supports programme objectives ( Apitz, 2008). The framework being considered for Canada’s DaS Program, like many DM frameworks, utilizes two SQGs – a Lower Action Level (LAL) and an Upper Action Level (UAL). Sediments which have contaminant levels below the LAL are deemed to pose negligible risk, and permits for uncontrolled open water disposal are granted without further analysis. Between the LAL and UAL, a tiered assessment examines lines of evidence to determine

whether contaminants present a risk, and above the UAL, sediments would go straight to a comparative risk assessment (CRA) to evaluate disposal options other than open water disposal. This framework allows for risk-based assessment, and thus it is designed to support risk-based (and not just reference-based) decisions. However, Amylase the application of both LAL and UAL allows for a separate evaluation of SQG selection at two levels in the decision process. As these two levels have different purposes and interpretive goals, the best choice of SQG type for one might not be the same as that for another. The addition of chemicals to the DaS action list in a LAL-only protocol resulted in a significant increase in the proportion of sediments that would require Tier 2 assessment to receive DaS permits; the degree to which this occurred depended upon the level of conservatism of the LALs applied. Similarly, a greater number of analytes added to a potential UAL action list had the same effects; the level of conservatism of the UAL values affected the proportion of sediments going to Tier 2 or failing.