Harold L. Bergman

Bio: Harold L. Bergman is an academic researcher from University of Wyoming. The author has contributed to research in topics: Trout & Rainbow trout. The author has an hindex of 37, co-authored 79 publications receiving 6494 citations. Previous affiliations of Harold L. Bergman include McMaster University & National Institute of Amazonian Research.

Hazard/Risk Assessment BIOTIC LIGAND MODEL OF THE ACUTE TOXICITY OF METALS. 1. TECHNICAL BASIS

Abstract: The biotic ligand model (BLM) of acute metal toxicity to aquatic organisms is based on the idea that mortality occurs when the metal-biotic ligand complex reaches a critical concentration. For fish, the biotic ligand is either known or suspected to be the sodium or calcium channel proteins in the gill surface that regulate the ionic composition of the blood. For other organisms, it is hypothesized that a biotic ligand exists and that mortality can be modeled in a similar way. The biotic ligand interacts with the metal cations in solution. The amount of metal that binds is determined by a competition for metal ions between the biotic ligand and the other aqueous ligands, particularly dissolved organic matter (DOM), and the competition for the biotic ligand between the toxic metal ion and the other metal cations in solution, for example, calcium. The model is a generalization of the free ion activity model that relates toxicity to the concentration of the divalent metal cation. The difference is the presence of competitive binding at the biotic ligand, which models the protective effects of other metal cations, and the direct influence of pH. The model is implemented using the Windermere humic aqueous model (WHAM) model of metal-DOM complexation. It is applied to copper and silver using gill complexation constants reported by R. Playle and coworkers. Initial application is made to the fathead minnow data set reported by R. Erickson and a water effects ratio data set by J. Diamond. The use of the BLM for determining total maximum daily loadings (TMDLs) and for regional risk assessments is discussed within a probabilistic framework. At first glance, it appears that a large amount of data are required for a successful application. However, the use of lognormal probability distributions reduces the required data to a manageable amount. Keywords—Bioavailability Metal toxicity Metal complexation Risk assessment

Biotic ligand model of the acute toxicity of metals. 1. Technical Basis

Abstract: The biotic ligand model (BLM) of acute metal toxicity to aquatic organisms is based on the idea that mortality occurs when the metal-biotic ligand complex reaches a critical concentration. For fish, the biotic ligand is either known or suspected to be the sodium or calcium channel proteins in the gill surface that regulate the ionic composition of the blood. For other organisms, it is hypothesized that a biotic ligand exists and that mortality can be modeled in a similar way. The biotic ligand interacts with the metal cations in solution. The amount of metal that binds is determined by a competition for metal ions between the biotic ligand and the other aqueous ligands, particularly dissolved organic matter (DOM), and the competition for the biotic ligand between the toxic metal ion and the other metal cations in solution, for example, calcium. The model is a generalization of the free ion activity model that relates toxicity to the concentration of the divalent metal cation. The difference is the presence of competitive binding at the biotic ligand, which models the protective effects of other metal cations, and the direct influence of pH. The model is implemented using the Windermere humic aqueous model (WHAM) model of metal-DOM complexation. It is applied to copper and silver using gill complexation constants reported by R. Playle and coworkers. Initial application is made to the fathead minnow data set reported by R. Erickson and a water effects ratio data set by J. Diamond. The use of the BLM for determining total maximum daily loadings (TMDLs) and for regional risk assessments is discussed within a probabilistic framework. At first glance, it appears that a large amount of data are required for a successful application. However, the use of lognormal probability distributions reduces the required data to a manageable amount.

Bioavailability: Physical, Chemical, and Biological Interactions

Abstract: Practical and provocative, Bioavailability reviews prevalent understanding of the physical-chemical-biological mechanisms that control the bioavailability of both organic and inorganic contaminants in aquatic environments * Discusses the complex issues that surround many regulatory issues * Emphasizes the need to identify and control that portion of the total concentration that is biologically available and can cause adverse effects, ie, "active" * Examines the influence of dynamic factors, such as pH, alkalinity, and light on these mechanisms * Addresses the subject of speciation for both organic and inorganic contaminants

Urea excretion as a strategy for survival in a fish living in a very alkaline environment.

Abstract: Ammonia is toxic to all vertebrates. It can be converted to the less toxic urea, but this is a metabolically expensive process found only in terrestrial vertebrates that cannot readily excrete ammonia and marine fish that use urea as an osmotic filler. Freshwater fish mostly excrete ammonia with only a small quantity of urea. It seems the ornithine cycle for urea production has been suppressed in all freshwater teleosts except for some airbreathers which, when exposed to air, increase urea synthesis via the cycle. Here we show that the tilapia fish Oreochromis alcalicus grahami, the only fish living in Lake Magadi, an alkaline soda lake (pH = 9.6-10) in the Kenyan Rift Valley, excretes exclusively urea and has ornithine-urea cycle enzymes in its liver. A closely related species that lives in water at pH 7.1 lacks these enzymes and excretes mainly ammonia with small amounts of urea produced via uricolysis. It dies within 60 min when placed in water from Lake Magadi. We suggest that urea production via the ornithine-urea cycle permits O. a. grahami to survive the very alkaline conditions in Lake Magadi.

Binding of Nickel and Copper to Fish Gills Predicts Toxicity When Water Hardness Varies, But Free-Ion Activity Does Not

Abstract: Based on a biotic-ligand model (BLM), we hypothesized that the concentration of a transition metal bound to fish gills ([Mgill]) will be a constant predictor of mortality, whereas a free-ion activity model is generally interpreted to imply that the chemical activity of the aquo (“free”) ion of the metal will be a constant predictor of mortality. In laboratory tests, measured [Nigill] and calculated [Cugill] were constant predictors of acute toxicity of Ni and Cu to fathead minnows (Pimephales promelas) when water hardness varied up to 10-fold, whereas total aqueous concentrations and free-ion activities of Ni and Cu were not. Thus, the BLM, which simultaneously accounts for (a) metal speciation in the exposure water and (b) competitive binding of transition-metal ions and other cations to biotic ligands predicts acute toxicity better than does free-ion activity of Ni or Cu. Adopting a biotic-ligand modeling approach could help establish a more defensible, mechanistic basis for regulating aqueous discharge...

Heavy metal toxicity and the environment.

Abstract: Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and Excretion of Nitrogenous Waste

Abstract: The fish gill is a multipurpose organ that, in addition to providing for aquatic gas exchange, plays dominant roles in osmotic and ionic regulation, acid-base regulation, and excretion of nitrogenous wastes Thus, despite the fact that all fish groups have functional kidneys, the gill epithelium is the site of many processes that are mediated by renal epithelia in terrestrial vertebrates Indeed, many of the pathways that mediate these processes in mammalian renal epithelial are expressed in the gill, and many of the extrinsic and intrinsic modulators of these processes are also found in fish endocrine tissues and the gill itself The basic patterns of gill physiology were outlined over a half century ago, but modern immunological and molecular techniques are bringing new insights into this complicated system Nevertheless, substantial questions about the evolution of these mechanisms and control remain

Hazard/Risk Assessment BIOTIC LIGAND MODEL OF THE ACUTE TOXICITY OF METALS. 1. TECHNICAL BASIS

Abstract: The biotic ligand model (BLM) of acute metal toxicity to aquatic organisms is based on the idea that mortality occurs when the metal-biotic ligand complex reaches a critical concentration. For fish, the biotic ligand is either known or suspected to be the sodium or calcium channel proteins in the gill surface that regulate the ionic composition of the blood. For other organisms, it is hypothesized that a biotic ligand exists and that mortality can be modeled in a similar way. The biotic ligand interacts with the metal cations in solution. The amount of metal that binds is determined by a competition for metal ions between the biotic ligand and the other aqueous ligands, particularly dissolved organic matter (DOM), and the competition for the biotic ligand between the toxic metal ion and the other metal cations in solution, for example, calcium. The model is a generalization of the free ion activity model that relates toxicity to the concentration of the divalent metal cation. The difference is the presence of competitive binding at the biotic ligand, which models the protective effects of other metal cations, and the direct influence of pH. The model is implemented using the Windermere humic aqueous model (WHAM) model of metal-DOM complexation. It is applied to copper and silver using gill complexation constants reported by R. Playle and coworkers. Initial application is made to the fathead minnow data set reported by R. Erickson and a water effects ratio data set by J. Diamond. The use of the BLM for determining total maximum daily loadings (TMDLs) and for regional risk assessments is discussed within a probabilistic framework. At first glance, it appears that a large amount of data are required for a successful application. However, the use of lognormal probability distributions reduces the required data to a manageable amount. Keywords—Bioavailability Metal toxicity Metal complexation Risk assessment