Commercial polychlorinated biphenyls (PCBs) and environmental extracts contain complex mixtures of congeners that can be unequivocally identified and quantitated. Some PCB mixtures elicit a spectrum of biochemical and toxic responses in humans and laboratory animals and many of these effects resemble those caused by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related halogenated aromatic hydrocarbons, which act through the aryl hydrocarbon (Ah)-receptor signal transduction pathway. Structure-activity relationships developed for PCB congeners and metabolites have demonstrated that several structural classes of compounds exhibit diverse biochemical and toxic responses. Structure-toxicity studies suggest that the coplanar PCBs, namely, 3,3',4,4'-tetrachlorobiphenyl (tetraCB), 3,3',4,4',5-pentaCB, 3,3',4,4',5,5'-hexaCB, and their monoortho analogs are Ah-receptor agonists and contribute significantly to the toxicity of the PCB mixtures. Previous studies with TCDD and structurally related compounds ...

Polychlorinated Biphenyls (PCBs): Environmental Impact, Biochemical and Toxic Responses, and Implications for Risk Assessment

Plastic debris litters aquatic habitats globally, the majority of which is microscopic (< 1 mm) and is ingested by a large range of species. Risks associated with such small fragments come from the material itself and from chemical pollutants that sorb to it from surrounding water. Hazards associated with the complex mixture of plastic and accumulated pollutants are largely unknown. Here, we show that fish, exposed to a mixture of polyethylene with chemical pollutants sorbed from the marine environment, bioaccumulate these chemical pollutants and suffer liver toxicity and pathology. Fish fed virgin polyethylene fragments also show signs of stress, although less severe than fish fed marine polyethylene fragments. We provide baseline information regarding the bioaccumulation of chemicals and associated health effects from plastic ingestion in fish and demonstrate that future assessments should consider the complex mixture of the plastic material and their associated chemical pollutants.

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Ingested plastic transfers hazardous chemicals to fish and induces hepatic stress

(1984). Polychlorinated Biphenyls (PCBs) and Polybrominated Biphenyls (PBBs): Biochemistry, Toxicology, and Mechanism of Action. CRC Critical Reviews in Toxicology: Vol. 13, No. 4, pp. 319-395.

Polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs): biochemistry, toxicology, and mechanism of action

Exposure and effects assessment of persistent organohalogen contaminants in arctic wildlife and fish.

Two distinct microbial processes, denitrification and anaerobic ammonium oxidation (anammox), are responsible for the release of fixed nitrogen as dinitrogen gas (N(2)) to the atmosphere. Denitrification has been studied for over 100 years and its intermediates and enzymes are well known. Even though anammox is a key biogeochemical process of equal importance, its molecular mechanism is unknown, but it was proposed to proceed through hydrazine (N(2)H(4)). Here we show that N(2)H(4) is produced from the anammox substrates ammonium and nitrite and that nitric oxide (NO) is the direct precursor of N(2)H(4). We resolved the genes and proteins central to anammox metabolism and purified the key enzymes that catalyse N(2)H(4) synthesis and its oxidation to N(2). These results present a new biochemical reaction forging an N-N bond and fill a lacuna in our understanding of the biochemical synthesis of the N(2) in the atmosphere. Furthermore, they reinforce the role of nitric oxide in the evolution of the nitrogen cycle.

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Molecular mechanism of anaerobic ammonium oxidation

A study of the metabolism of theobromine, theophylline, and caffeine in man.

Potentiation of carbon tetrachloride toxicity by aliphatic alcohols.

Biological responses of the rat to polychlorinated biphenyls.

This study was undertaken to determine the potentiating action of prior ethanol ingestion on the toxicity of carbon tetrachloride, trichloroethylene, perchloro-ethylene, and 1,1,1-trichloroethylene. Ethanol potentiation of toxicity, as measured by serum enzyme response, could be demonstrated only after exposure of rats to carbon tetrachloride or trichloroethylene.

Herbert H. Cornish

Papers

A study of the metabolism of theobromine, theophylline, and caffeine in man.

Potentiation of carbon tetrachloride toxicity by aliphatic alcohols.

Biological responses of the rat to polychlorinated biphenyls.

Ethanol Potentiation of Halogenated Aliphatic Solvent Toxicity

Effect of pretreatment of rats with carbon tetrachloride on tolerance development