Evaluating the Protectiveness of a Bioavailability-Based Environmental Quality Standard for the Protection of Aquatic Communities from Zinc Toxicity Based on Field Evidence.

Environmental quality standards (EQS) are typically derived from the results of laboratory studies on single species. There is always uncertainty surrounding the protectiveness of an EQS when applied to real ecosystems containing a multitude of chemical and physical stressors. Quantile regression was used with field biological data on invertebrates in United Kingdom waters to identify taxa that are responsive to bioavailable zinc exposures. A threshold based on the total abundance of eight responsive taxa is used as an indicator of the overall ecosystem sensitivity. The inclusion of some responsive but insensitive taxa in this ecological metric could bias the results toward a higher threshold. The least responsive species were progressively removed from the collective ecological metric, basing the analysis on a progressively smaller number of the more responsive species. Quantile regression analysis at the 95th quantile for the three most responsive taxa resulted in a 10% effect concentration of 14.8 µg L-1 bioavailable zinc, suggesting that the EQS of 10.9 µg L-1 bioavailable zinc is sufficiently protective of sensitive members of the invertebrate community. There is a compromise between the robustness of the analysis and the sensitivity of the subcommunity that it is based on. Analyses based on fewer taxa provide a more sensitive result. This approach assessed real ecosystem data and evaluated the uncertainty associated with the protectiveness of the EQS for zinc. The zinc EQS is sufficiently protective of sensitive members of benthic macroinvertebrate communities under real environmental conditions, including a mix of multiple substances. Environ Toxicol Chem 2023;42:1010-1021. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Deriving a bioavailability-based zinc environmental quality standard for France.

National Environmental Quality Standards (EQS) for zinc used for the assessment of ecological status in freshwaters have been shown to vary by over two orders of magnitude across 25 European countries. Such variability is unlikely to reflect consistent ecological protection or environmental relevance. Recent European technical guidance on EQS derivation gives an opportunity to derive protective metrics for zinc that are relevant to national water chemistry conditions. To derive a zinc EQS relevant to national water chemistry conditions and account for bioavailability, the new technical guidance requires high-quality spatial and temporal monitoring data. These data must be of water samples with concurrent measures of pH, dissolved organic carbon (DOC) and calcium, the parameters that most influence zinc bioavailability in freshwaters. A national bioavailability-based zinc EQS for France has been derived from Biotic Ligand Model calculations undertaken for freshwaters samples from 4645 sites (22,000 samples with concurrent measures of pH, DOC, calcium) in 96 regions. An EQS of 11.3 µg Zn L-1 was derived based on sensitive waters from the Bretagne region typically of circumneutral pH and relatively low DOC and low dissolved calcium. The least sensitive waters to zinc exposures in France are found in the Hauts-De-France, higher pH values than those in Bretagne, similar dissolved organic carbon and higher dissolved calcium. An indicative assessment of compliance showed that across France, 2% of the sites would exceed this bioavailability-based EQS.

Demonstrating the Reliability of bio-met for Determining Compliance with Environmental Quality Standards for Metals in Europe.

The importance of considering the bioavailability of metals in understanding and assessing their toxicity in freshwaters has been recognized for many years. Currently, biotic ligand models (BLMs) are being applied for the derivation and implementation of environmental quality standards (EQS) for metals under the Water Framework Directive in Europe. bio-met is a simplified tool that was developed for implementing bioavailability-based EQS for metals in European freshwaters. We demonstrate the reliability of the relationship between the full BLM predictions and the thresholds (hazardous concentration affecting 5% of species [HC5] values) predicted by bio-met in 3 stages, for the metals copper, nickel, and zinc. First, ecotoxicity data for specific species from laboratory tests in natural waters are compared with predictions by the individual species BLMs included in the full BLMs. Second, the site-specific HC5 values predicted by bio-met for the natural waters used for ecotoxicity testing are compared with those provided by the full BLMs. The reliability of both relationships is demonstrated for all 3 metals, with more than 80% of individual species BLM predictions being within a factor of 3 of the experimental results, and 99% of bio-met local HC5 predictions being within a factor of 2 of the full BLM result. Third, using a larger set of European natural waters in addition demonstrates the reliability of bio-met over a broad range of water chemistry conditions. bio-met is therefore an appropriate tool for performing compliance assessments against EQS values in Europe, due to the demonstrated consistency with the toxicity test data. Environ Toxicol Chem 2020;39:2361-2377. © 2020 SETAC.

Inter-laboratory validation of bioaccessibility testing for metals.

Bioelution assays are fast, simple alternatives to in vivo testing. In this study, the intra- and inter-laboratory variability in bioaccessibility data generated by bioelution tests were evaluated in synthetic fluids relevant to oral, inhalation, and dermal exposure. Using one defined protocol, five laboratories measured metal release from cobalt oxide, cobalt powder, copper concentrate, Inconel alloy, leaded brass alloy, and nickel sulfate hexahydrate. Standard deviations of repeatability (sr) and reproducibility (sR) were used to evaluate the intra- and inter-laboratory variability, respectively. Examination of the sR:sr ratios demonstrated that, while gastric and lysosomal fluids had reasonably good reproducibility, other fluids did not show as good concordance between laboratories. Relative standard deviation (RSD) analysis showed more favorable reproducibility outcomes for some data sets; overall results varied more between- than within-laboratories. RSD analysis of sr showed good within-laboratory variability for all conditions except some metals in interstitial fluid. In general, these findings indicate that absolute bioaccessibility results in some biological fluids may vary between different laboratories. However, for most applications, measures of relative bioaccessibility are needed, diminishing the requirement for high inter-laboratory reproducibility in absolute metal releases. The inter-laboratory exercise suggests that the degrees of freedom within the protocol need to be addressed.

Development of realistic environmental release factors based on measured data: approach and lessons from the EU metal industry.

The assessment of environmental exposure and risks associated with the production or use of a substance on an industrial site includes the estimation of the releases to the environment. In the absence of measured release data on the specific substance, a risk assessor would rely on default release factors to the environmental compartments as developed in international, national, or regional context. Because a wide variety of substances, processes, and uses has to be covered, default release factors are as a rule conservative, usually leading to significant overprediction of releases and hence to overpredicted environmental exposure concentrations and risks. In practice, unrealistic and worst-case predictions do not support a more efficient management of releases and risk. The objective of this article is to propose a more realistic approach to characterize the environmental releases from manufacture, processing, and downstream uses of the metals and their compounds. Although developed in the European Union (EU), this approach can also be used in other regions and in other chemical management systems addressing metals. A database consisting of more than 1300 recent (1993-2010), site-specific measured release factors to air and water of 18 different metals from various EU Member States was compiled and used to calculate average and reasonable worst-case release factors for multiple metal manufacture and industrial use processes. The parameters influencing releases to water were found to depend predominantly on life cycle step (manufacture and/or use), the sector and/or the solid-water partition coefficient (K(d)). The release factors can be used as advanced tier instrument in environmental safety assessments, increasing the realism of the estimates while still keeping a sufficient level of conservatism.