Toxicological and environmental significance

Most of the arsenic compounds that enter the environment undergo chemical transformation. With the exception of the arsenite-arsenate conversion, facilitated by the redox potential of the surrounding media, the transformation reactions are biochemically 

Arsenic speciation in the environment, with particular emphasis on marine and aquatic systems, has been comprehensively reviewed recently (Cullen and Reimer, 1989). 

In the eighties a technical panel of EPA reviewed several studies on arsenic as a possible essential element in human diet. Since inconsistent results were found in animal studies and many uncertainties remained, the panel determined that at present, the case for arsenic essentiality is not proven for animals, and is even less certain for humans (Gostomski, 1987). 

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This fraction consists entirely of PAHs. The more environmentally and toxicologically significant PAHs are the subjects of the ATSDR toxicological profile on PAHs (ATSDR 1995f) two of these PAHs, acenaphthene and acenaphthylene, are constituents of the EC>12-EC16 fraction, discussed previously, and the remaining 15 are constituents of the EC>16-EC35 combined fraction, described below. 

The importance of toxic elements in environmental chemistry is rarely questioned, but a relatively small number of elements (mercury, lead, and cadmium) have received a large share of researchers attention. The environmental chemistry of the transition metals, e.g., chromium, nickel, manganese, cobalt, copper, etc., has also been investigated principally because of their roles in metabolism, especially enzymatic processes. However, two non-metals, arsenic and selenium, and two metals, beryllium and vanadium, are elements which will become more significant in the future from environmental and toxicological points of view. Arsenic and selenium have been investigated, but much more work is needed because of the importance of these two elements in the environment. The author considers beryllium and vanadium to be problem metals of the future . The primary exposure route for both beryllium and vanadium is via the atmosphere and as lower environmental standards are imposed, more uses are found for each element, and more fossil fuels (source of V) are burned, the amounts added to the atmosphere will have more significance. 

Moreover, a-, p- and y-HBCD diastereoisomers are chiral. Thus HBCD have three pairs of enantiomers (+)a, (—)a, (+)p, (—)p, (+)y and (—)y. The enantiomers have identical physicochemical properties and abiotic degradation rates, but may have different biological and toxicological properties and therefore different biotransformation rates. These transformations may result in nonracemic mixtures of the enantiomers that were industrially synthesized as racemates [16, 19]. The rates of metabolisation process of the enantiomers of chiral environmental pollutants may be significantly different [20],... 

Wiener, J.G. and D.J. Spry. 1996. Toxicological significance of mercury in freshwater fish. Pages 297-339 in W.N. Beyer, G.H. Heinz, and A.W. Redmon-Norwood (eds.). Environmental Contaminants in Wildlife Interpreting Tissue Concentrations. CRC Press, Boca Raton, FL. 

Introduction The inherent nature of most chemicals handled in the chemical process industries is that they each have physical, chemical, and toxicological hazards to a greater or lesser degree. This requires that these hazards be contained and controlled throughout the entire life cycle of the facility, to avoid loss, injury and environmental damage. The provisions that will be necessary to contain and control the hazards will vary significantly depending on the chemicals and process conditions required. 

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