ABSTRACT While water quality benchmarks for the protection of aquatic life have been in use in some jurisdictions for several decades (USA, Canada, several European countries), more and more countries are now setting up their own national water quality benchmark development programs. In doing so, they either adopt an existing method from another jurisdiction, update on an existing approach, or develop their own new derivation method. Each approach has its own advantages and disadvantages, and many issues have to be addressed when setting up a water quality benchmark development program or when deriving a water quality benchmark. Each of these tasks requires a special expertise. They may seem simple, but are complex in their details. The intention of this paper was to provide some guidance for this process of water quality benchmark development on the program level, for the derivation methodology development, and in the actual benchmark derivation step, as well as to point out some issues (notably the inclusion of adapted populations and cryptic species and points to consider in the use of the species sensitivity distribution approach) and future opportunities (an international data repository and international collaboration in water quality benchmark development).
Predicted no effect concentration (PNEC) derivation as a significant source of variability in environmental hazard assessments of chemicals in aquatic systems: An international analysis.
ABSTRACT Many jurisdictions around the globe have well-developed regulatory frameworks for the derivation and implementation of water quality guidelines (WQGs) or their equivalent (e.g. environmental quality standards, criteria, objectives or limits). However, a great many more still do not have such frameworks and are looking to introduce practical methods to manage chemical exposures in aquatic ecosystems. There is a potential opportunity for learning and sharing of data and information between experts from different jurisdictions in order to deliver efficient and effective methods to manage potential aquatic risks, including the considerable reduction in the need for aquatic toxicity testing and the rapid identification of common challenges. This paper reports the outputs of an international workshop with representatives from 14 countries held in Hong Kong in December 2011. The aim of the workshop and this paper was to identify 'good practice' in the development of WQGs to deliver to a range of environmental management goals. However, it is important to broaden this consideration to cover often overlooked facets of implementable WQGs, such as demonstrable field validation (i.e. does the WQG protect what it is supposed to?), fit for purpose of monitoring frameworks (often an on-going cost) and finally how are these monitoring data used to support management decisions in a manner that is transparent and understandable to stakeholders. It is clear that regulators and the regulated community have numerous pressures and constraints on their resources. Therefore, the final section of this paper addresses potential areas of collaboration and harmonisation. Such approaches could deliver a consistent foundation from which to assess potential chemical aquatic risks, including, for example, the adoption of bioavailability-based approaches for metals, whilst reducing administrative and technical burdens in jurisdictions.
ABSTRACT: This chapter deals with the derivation of aquatic EQSs, including standards for the protection of water dwellers, predators of water dwellers, and human water users. However, the main focus is on standards for the protection of organisms that live in water or aquatic sediment and are able to absorb contaminants directly via their gills, skin and/or cell surfaces. In other words, the chapter primarily covers the derivation of standards for the protection of aquatic ecosystems.
03/2010: pages 47-103; , ISBN: 978-1-4398-0344-8
Reducing uncertainty in environmental risk assessment (ERA): clearly defining acute and chronic toxicity tests.
ABSTRACT: 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.
Comparative Biochemistry and Physiology Part C Toxicology & Pharmacology 10/2002; 133(1-2):3-35.
ABSTRACT: Fixed aliquots of both radiolabeled [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and hepatic Ah receptor from C57BL/6J mice were incubated competitively at 4, 23, and 30 degrees C with mixtures of 2,3,7,8-TCDD and several polychlorinated biphenyls (PCBs). The production of the radiolabeled receptor-ligand complex changed if the ligands were added sequentially, demonstrating that the competition between PCBs and TCDD for the Ah receptor in vitro is principally a kinetic rather than an equilibrium phenomenon and is irreversible on the time scale of our in vitro experiments. Examination of previous reports on the ability of TCDD, PCBs, and their mixtures to induce cleft palate in fetal mice suggests that the potency of receptor-ligand complexes is ligand-dependent. Receptor occupancy is not a sufficient condition for toxicity, and protection by one ligand against the toxic effect of a second, more potent one is only possible when a significant fraction of receptors is occupied.
Toxicology and Applied Pharmacology 01/1995; 129(2):243-51.
ABSTRACT: Estimates have been obtained for all half-lives of several chlorinated aliphatic pollutants in the Canadian troposphere. The rates of reaction are strongly dependent on the magnitude of the second-order rate constant for reaction of the pollutant with OH, and on the intensity of solar radiation , which is determined both by season and geographical location. Of the pollutants studied, trichloroethylene has the shortest half-life of 2–5 days in summer, depending on location. Dichloromethane, 1,2-dichloroethane and tetrachloroethylene are each about one order of magnitude longer lived than trichloroethylene; 1,1,1-trichloroethane and 1,1,2,2-tetrachloroethane are about two orders of magnitude longer lived than trichloroethylene. Under urban conditions, high rates of oxidation, and hence short half-lives, are favoured by high tropospheric concentrations of ozone and low concentrations of NO2. With the exception of 1,1,1-trichloroethane, none of these substances is predicted to pose a significants threat to stratospheric ozone.
Journal of Photochemistry and Photobiology A-chemistry - J PHOTOCHEM PHOTOBIOL A-CHEM. 01/1994; 81(2):93-101.
ABSTRACT: Chlorinated trans stilbenes bind with high affinity to the cytosolic Ah receptor from Wistar rat liver. The EC50 values for competition with [H]?2,3,7,8?tetrachlorodibenzo?p?dioxin (TCDD) cover a range from 10–400 nM, but with no apparent relationship between molecular structure and binding activity. These compounds induce monooxygenase enzyme activity in rat hepatoma H?4?II E cells in culture only weakly, again with no apparent dependence on molecular structure, and the weakest enzyme inducers act as antagonists for the induction of these enzymes by TCDD. In vivo administration of 3,3’,4,4'?tetrachloro?tans?stilbene in the rat leads to decreased Ah receptor levels.
ABSTRACT: An assay for mixtures of PCDD-like compounds is being developed, based on the competitive binding of the mixture and a fixed aliquot of radiolabelled [3H]-TCDD towards the mouse hepatic Ah receptor protein. The results are expressed in terms of the concentration of unlabelled TCDD which produces the same response as the mixture. Preliminary experiments indicate that mixtures behave additively in this assay.
I am offering a set of standard training courses (1-, viagra 100mg and 2-days) on ambient water quality issues and water quality benchmarks in Canada and internationally. These courses are custom-designed to meet the needs of newcomers as well as seasoned practitioners related to water quality issues. The courses are important for anyone working in the aquatic toxicity field or with water quality benchmarks. For the dates, location, sales and registration for the various courses currently offered, please visit “Upcoming Events”
Course 1: Introduction to the Canadian Water Quality Guidelines for the Protection of Aquatic Life -their history, purpose, derivation, application, and interpretation, ; their factsheets and supporting documentation, etc. - … “Guidelines 101” (see below / click here for the course abstract)
Course 2: Overview on the Derivation Methods for Site-Specific Water Quality Benchmarks for the Protection of Aquatic Life - advantages and disadvantages of the various derivation methods, proper process, potential errors and mistakes (see below / click here for the course abstract)
Course 3: How to properly derive a Water Quality Benchmark for the Protection of Aquatic Life - generic and site-specific
Course 4: How to critically review and evaluate a Water Quality Benchmark for the Protection of Aquatic Life - generic and site-specific
These courses are generally offered in the Ottawa (Ontario, Canada) area, however, I can teach them in other locations if desired.