Assessing the fit of biotic ligand model validation data in a risk management decision context

Abstract

Biotic ligand models (BLMs) have advanced the ability to predict the concentrations of metals in surface waters likely to harm aquatic organisms. BLMs have been developed for several metals including Cu, Zn, Cd, and Ag. Additionally, the US Environmental Protection Agency has published guidance on the use of a BLM to develop water quality criteria for Cu. To validate the predictive performance of many BLMs, model predictions based on test water quality have been compared with corresponding laboratory toxicity measurements. Validation results are typically described in the published literature in terms of the proportion of predicted effect concentrations that fall within a factor of 2 of measured values. In this article, an alternative is presented using a receiver operating characteristics approach and regression prediction limit analyses, quantifying the probabilities of true and false predictions of excess toxicity risk based on toxic unit calculations and a risk management threshold of 1. The approaches are applied to a published Zn BLM and 3 simulated data sets that reflect attributes of other published BLM validation data. The overall accuracy of the unified Zn BLM is estimated to be 80% to 90%, and analyses of simulated data suggest a similar level of accuracy for other published BLMs. Further application of these validation methods to other BLMs may provide more complete and transparent information on their possible predictive value when used in the management of risks due to aqueous metals.

Site-specific water quality criteria for lethal/sublethal protection of freshwater fish exposed to zinc in southern Taiwan

“…Verschoor et al (2011) used the BLM to assess the temporal-and geographical-dependent risk characterization rations that were derived by dividing site-specific adverse effect level (ECx or LCx). The BLM-based WQC has been widely used for the risk management decision context in several countries, such as US, European Union, and UK (WFD-UKTAG, 2014; Lathouri and Korre, 2015;McLaughlin, 2015;Rüdel et al, 2015). However, the protectiveness of current WQC based on metal bioavailability for metal toxicity to aquatic organism is still unclear in Taiwan.…”

“…As expected, high cation contents of Agongdian and Love Rivers heavily decreased Zn bioavailability in the higher WER conditions. Recent studies indicated that the site-specific bioavailabilitybased approach is considered to be the best one to account for the environmental quality standard and risk management of regional and local water chemistry characteristics in regulatory organizations (Lathouri and Korre, 2015;McLaughlin, 2015;Rüdel et al, 2015). Verschoor et al (2011) used the BLM to assess the temporal-and geographical-dependent risk characterization rations that were derived by dividing site-specific adverse effect level (ECx or LCx).…”

“…The biotic ligand model (BLM) has been developed intensively to account implicitly for the effect of water chemistry on the metal bioavailability. The BLM can be used to establish the site-specific environmental quality criteria and risk assessment framework (Lathour and Korre, 2015;McLaughlin, 2015;Rüdel et al, 2015). The EU Scientific Committee on Health and Environmental Risk has incorporated the BLM into the risk assessment framework (SCHER, 2007).…”

Contaminant curiosity and pollutant puzzles: Conceptual insights in ecotoxicity and practical implementation of higher-tiered risk assessment.

“…The capability of BLM to differentiate locations in terms of risks was reviewed by many authors (e.g. DeSchamphelaere et al, 2005; Van Sprang et al, 2009; McLauglin, 2015).…”

How Specific Is Site‐Specific? A Review and Guidance for Selecting and Evaluating Approaches for Deriving Local Water Quality Benchmarks

“…In recognition of the abovementioned limitations, BLMs are validated using synthetic and natural waters prior to being considered acceptable for broader use, with their acceptability being assessed by determining the proportion of predictions (based on test water chemistry) that fall within a factor of 2 of the actual observed toxicity (McLaughlin ). The literature suggests that a BLM is considered acceptable if more than 90% of the predictions fall within a factor of 2 of the observed toxicity (Bury et al ; Niyogi and Wood ; Peters, Lofts et al ; Nys et al ).…”