Weight-of-evidence WOE approaches

In announcing the details of the Endocrine Disruptor Screening Program (EDSP), the EPA stated that a weight-of-evidence (WOE) approach would be used to evaluate Tier I and Tier II results. Moreover, the WOE approach will include consideration of ... 

Figure 5.7 Weight-of-evidence (WOE) approach in assessing mixture effects. Three Lines of Evidence (LOE) are considered, in a tiered fashion (simple and quick methods in the tier-1, more complex methods in higher tiers). For each LOE, the response is scaled between 0 and 1. The LOEs can indicate a similar type of response, which results in a low Coefficient of Variation (CV), or differences (high CV). When the CV is lower than a predefined value, the assessment is stopped, and a decision (e.g., on remediation) is taken. TU = Toxic Unit, PAF = Probably Affected Fraction of species.

There has been progress in establishing protocols for confirming risks or at least the likelihood that a cause-effect relationship may exist. Two of the methods are the use of specific criteria for the establishment of causation, and the other is the weight of evidence (WoE) approach. 

The framework for analyzing MOA begins with a summary description of the postulated MOA. The judgment of whether a postulated MOA is supported by available data takes into account all of the data in a weight of evidence (WOE) approach. MOA analysis must determine the links between the postulated key events and tumor induction including (i) strength, consistency, and specificity of association, (ii) dose-response relationships between the key events and tumor induction,... 

The approaches discussed are the hazard index (HI) (Section 10.5.1.1) and the weight-of-evidence (WOE) modification to the HI (Section 10.5.1.2), the point of departure index (PODl) (Section 10.5.1.3), toxicity equivalency factors (TEFs) (Section 10.5.1.4), the margin of exposure (MOE) procedures (Section 10.5.1.5), and the cumulative risk index (CRl) method (Section 10.5.1.6). 

The Sediment Quality Triad (SQT) is an effects-based conceptual approach that can be used to assess and determine the status of contaminated sediments based on biology (laboratory and/or in situ toxicity tests), chemistry (chemical identification and quantification), and ecology (community structure and/or function). It provides a means for comparing three different lines of evidence (LOE) and arriving at a weight of evidence (WOE) determination regarding the risk posed by contaminated sediments. Effectively, each LOE comprises an independent assessment of hazard combined and integrated, they provide an assessment of risk. 

Kirkland, D.J., Aardema, M., Banduhn, N., CarmichaeL P, Fautz, R., Meunier, J.-R., Pfuhler, S. (2007). In vitro approaches to develop weight of evidence (WoE) and mode of action (MoA) discussions with positive in vitro genotoxicity results. Mutagenesis, 22, 161-175. 

The weight-of-evidence approach (WOE) is becoming increasingly important for ERA in terrestrial ecosystems. There is a broad range of bioassays, biomarkers and ecological field parameters applicable. Different kinds of implementation levels... 

---