Robert L. Dwyer

The biotic ligand model: a historical overview

During recent years, the biotic ligand model (BLM) has been proposed as a tool to evaluate quantitatively the manner in which water chemistry affects the speciation and biological availability of metals in aquatic systems. This is an important consideration because it is the bioavailability and bioreactivity of metals that control their potential to cause adverse effects. The BLM approach has gained widespread interest amongst the scientific, regulated and regulatory communities because of its potential for use in developing water quality criteria (WQC) and in performing aquatic risk assessments for metals. Specifically, the BLM does this in a way that considers the important influences of site-specific water quality. This journal issue includes papers that describe recent advances with regard to the development of the BLM approach. Here, the current status of the BLM development effort is described in the context of the longer-term history of advances in the understanding of metal interactions in the environment upon which the BLM is based. Early developments in the aquatic chemistry of metals, the physiology of aquatic organisms and aquatic toxicology are reviewed first, and the degree to which each of these disciplines influenced the development of water quality regulations is discussed. The early scientific advances that took place in each of these fields were not well coordinated, making it difficult for regulatory authorities to take full advantage of the potential utility of what had been learned. However, this has now changed, with the BLM serving as a useful interface amongst these scientific disciplines, and within the regulatory arena as well. The more recent events that have led to the present situation are reviewed, and consideration is given to some of the future needs and developments related to the BLM that are envisioned. The research results that are described in the papers found in this journal issue represent a distinct milestone in the ongoing evolution of the BLM approach and, more generally, of approaches to performing ecological assessments for metals in aquatic systems. These papers also establish a benchmark to which future scientific and regulatory developments can be compared. Finally, they demonstrate the importance and usefulness of the concept of bioavailability and of evaluative tools such as the BLM.

A Weight-of-Evidence Framework for Assessing Sediment (Or Other) Contamination: Improving Certainty in the Decision-Making Process

A basic framework is presented for the ecological weight-of-evidence (WOE) process for sediment assessment that clearly defines its essential elements and will improve the certainty of conclusions about whether or not impairment exists due to sediment contamination, and, if so, which stressors and biological species (or ecological responses) are of greatest concern. The essential “Certainty Elements” are addressed in a transparent best professional judgment (BPJ) process with multiple lines-of-evidence (LOE) ultimately quantitatively integrated (but not necessarily combined into a single value). The WOE Certainty Elements include: (1) Development of a conceptual model (showing linkages of critical receptors and ecosystem quality characteristics); (2) Explanation of linkages between measurement endpoint responses (direct and indirect with associated spatial/temporal dynamics) and conceptual model components; (3) Identification of possible natural and anthropogenic stressors with associated exposure dynamics; (4) Evaluation of appropriate and quantitatively based reference (background) comparison methods; (5) Consideration of advantages and limitations of quantification methods used to integrate LOE; (6) Consideration of advantages and limitations of each LOE used; (7) Evaluation of causality criteria used for each LOE during output verification and how they were implemented; and (8) Combining the LOE into a WOE matrix for interpretation, showing causality linkages in the conceptual model. The framework identifies several statistical approaches for integrating within LOE, the suitability of which depends on physical characteristics of the system and the scale/nature of impairment. The quantification approaches include: (1) Gradient (regression methods); (2) Paired reference/test (before/after control impact and ANOVA methods); (3) Multiple reference (ANOVA and multivariate methods); and 4) Gradient with reference (regression, ANOVA and multivariate methods). This WOE framework can be used for any environmental assessment and is most effective when incorporated into the initial and final study design stages (e.g., the Problem Formulation and Risk Characterization stages of a risk assessment) with reassessment throughout the project and decision-making process, rather than in a retrospective data analysis approach where key certainty elements cannot be adequately addressed.

Modeling and interpreting biological effects of mixtures in the environment: Introduction to the metal mixture modeling evaluation project

The fate and biological effects of chemical mixtures in the environment are receiving increased attention from the scientific and regulatory communities. Understanding the behavior and toxicity of metal mixtures poses unique challenges for incorporating metal-specific concepts and approaches, such as bioavailability and metal speciation, in multiple-metal exposures. To avoid the use of oversimplified approaches to assess the toxicity of metal mixtures, a collaborative 2-yr research project and multistakeholder group workshop were conducted to examine and evaluate available higher-tiered chemical speciation-based metal mixtures modeling approaches. The Metal Mixture Modeling Evaluation project and workshop achieved 3 important objectives related to modeling and interpretation of biological effects of metal mixtures: 1) bioavailability models calibrated for single-metal exposures can be integrated to assess mixture scenarios; 2) the available modeling approaches perform consistently well for various metal combinations, organisms, and endpoints; and 3) several technical advancements have been identified that should be incorporated into speciation models and environmental risk assessments for metals.

Bioaccumulation of trace metals in Mediterranean mussels (Mytilus galloprovincialis) from a fish farm with copper-alloy mesh pens and potential risk assessment

ABSTRACT Concentrations of trace metals were determined in the muscle tissue, digestive gland and gills of Mediterranean mussels (Mytilus galloprovincialis) collected from different locations around an offshore copper alloy fish farm. Levels of copper (Cu), zinc (Zn), manganese (Mn) and iron (Fe) as mg/kg wet weight in the edible part of the mussels collected from distant zone (upstream Zn7.33 > Fe2.8 > Cu0.13 > Mn0.07 and downstream Zn9.9 > Fe5.67 > Cu0.18 > Mn0.17) were significantly lower (p < 0.05) than those sampled from the cage zone (bottom panel Zn22.25 > Fe13.75 > Cu2.39 > Mn0.85 and cage frame Zn17.1 > Fe8.74 > Cu1.39 > Mn0.26). Trace metal concentrations in mussels were significantly higher (p < 0.05) in the samples from the frame and bottom panel of the copper alloy mesh pen, compared to those from distant areas, namely the farm affected downstream -and non-affected upstream locations. However, the rates of target hazard quotients (THQ) for all tested trace metals from all locations in the present study were smaller than “one” (THQ < 1), indicating that the consumption of mussels grown around a cage farm with copper alloy mesh pens were within safe limits and did not exceed maximum levels suggested by the US Food and Drug Administration (USFDA) and European Union (EU) regulations for seafood consumption.

Toward Harmonizing Ecotoxicity Characterization in Life Cycle Impact Assessment

Ecosystem quality is an important area of protection in life cycle impact assessment (LCIA). Chemical pollution has adverse impacts on ecosystems on a global scale. To improve methods for assessing ecosystem impacts, the Life Cycle Initiative hosted by the United Nations Environment Programme established a task force to evaluate the state-of-the-science in modeling chemical exposure of organisms and the resulting ecotoxicological effects for use in LCIA. The outcome of the task force work will be global guidance and harmonization by recommending changes to the existing practice of exposure and effect modeling in ecotoxicity characterization. These changes will reflect the current science and ensure the stability of recommended practice. Recommendations must work within the needs of LCIA in terms of 1) operating on information from any inventory reporting chemical emissions with limited spatiotemporal information, 2) applying best estimates rather than conservative assumptions to ensure unbiased comparison with results for other impact categories, and 3) yielding results that are additive across substances and life cycle stages and that will allow a quantitative expression of damage to the exposed ecosystem. We describe the current framework and discuss research questions identified in a roadmap. Primary research questions relate to the approach toward ecotoxicological effect assessment, the need to clarify the methods scope and interpretation of its results, the need to consider additional environmental compartments and impact pathways, and the relevance of effect metrics other than the currently applied geometric mean of toxicity effect data across species. Because they often dominate ecotoxicity results in LCIA, we give metals a special focus, including consideration of their possible essentiality and changes in environmental bioavailability. We conclude with a summary of key questions along with preliminary recommendations to address them as well as open questions that require additional research efforts. Environ Toxicol Chem 2018;37:2955-2971.

CONSTRUCTION, ASSEMBLY AND SYSTEM DEPLOYMENT OF A FISH CAGE WITH COPPER ALLOY MESH PEN: CHALLENGING WORK LOAD AND ESTIMATION OF MAN-POWER

In the present study, a 150 cubic m net pen was designed as part of a collaborative research effort between the International Copper Association (ICA-USA), the University of New Hampshire (UNH-USA) and Cannakale Onsekiz Mart University (COMU-Turkey) in August 2011. The fish cage was developed to support the creation of a small scale demonstration farm, located in the Strait of Canakkale, off the coast of Guzelyali town in Turkey. The surface gravity-type, octagonal shaped fish cage was designed to have a diameter of 6 m and a copper alloy mesh chamber depth of 5 m. The present study details the cage construction and system deployment of one fish cage utilized a chain link mesh net chamber with a copper alloy developed by Wieland-Werke in Germany, with reference to work load challenge and estimation of man-power necessary for the partial and total work efforts. As a conclusion, one cage equipped with copper-alloy mesh pen was brought to a final shape with the net chamber assembled and attached to the cage frame in 3 days and 90 man-hours. The HDPE (high density polythylene) cage frame was assembled by an outside company, therefore detail of the main cage frame is not discussed in this paper.

Misapplication of generic hazard-classification schemes for versatile, sustainable building materials: Copper as an example

ABSTRACT Decisions regarding the use of building materials are being made based solely on the hazards of chemicals, without conducting risk assessments that account for realistic potential exposures and effects. We present copper as an example of a versatile, sustainable building material for which hazard classification has been misapplied. As a result, copper has been “blacklisted” for use as an exterior building material. However, its purported human health effects are not relevant for exposure to exterior building materials; furthermore, the potential environmental effects to aquatic life are not considered in appropriate contexts. We recommend evaluating risks of copper in runoff water at the point in temporal, chemical, and physical spaces at which organisms of concern will be exposed, instead of evaluating copper concentrations at the point of runoff from copper roofs, gutters, etc. Instead of banning a building material, appropriate institutional controls and/or best management practices should be required to control the release of related substances, if needed. In the absence of risk and/or life cycle assessments, architects and builders might choose regrettable substitutions in which materials posing unknown but potentially higher risks will replace more completely characterized materials that have lower risk in a given application.