Toxic metals and metalloids

Wong, H.K.T., Gauthier, A., Beauchamp, S. and Tordon, R. (2002) Impact of toxic metals and metalloids from the Caribou gold-mining areas in Nova Scotia, Canada. Geochemistry Exploration, Environment, Analysis, 2(3), 235-41. 

It is well known that a large number of chemical substances, including toxic metals and metalloids such as arsenic, cadmium, lead, and mercury, cause cell injury in the kidney. With metal-induced neurotoxicity, factors such as metal-binding proteins, inclusion bodies, and cell-specific receptor-like proteins seem to influence renal injury in animals and humans. It is of interest to note that certain renal cell populations become the targets for metal toxicity, while others do not. In fact, the target cell populations handle the organic and common inorganic nephrotoxicants differently. ... 

Drexler J., Mushak P., 1994. Health risks from extractive industry wastes an approach to bioavailability of toxic metal and metalloidal contaminants. Annual Meeting of the Geological Society of America, October 24—27, 1994, Seattle, WA. 

The 12 toxic metals and metalloids on the Resource Conservation and Recovery Act (RCRA) list are investigated most often. Of these, arsenic, lead, chromium (VI), and cadmium top the list of toxicants most frequently found above toxicity thresholds at Superfund sites 103). Due to the prevalence of metals in the environment and the fact that many metals are essential nutrients... 

In the past, removing metal and metalloid contaminants from soil has been impossible, and site clean-up has meant excavation and disposal in a secure landfill. An exciting new approach to this problem is phytoextraction, where plants are used to extract contaminants from the soil and harvested. Immobilization and Toxicity-Minimization. 

Arsenic is another element with different bioavailabiUty in its different redox states. Arsenic is not known to be an essential nutrient for eukaryotes, but arsenate (As(V)) and arsenite (As(III)) are toxic, with the latter being rather more so, at least to mammals. Nevertheless, some microorganisms grow at the expense of reducing arsenate to arsenite (81), while others are able to reduce these species to more reduced forms. In this case it is known that the element can be immobilized as an insoluble polymetallic sulfide by sulfate reducing bacteria, presumably adventitiously due to the production of hydrogen sulfide (82). Indeed many contaminant metal and metalloid ions can be immobilized as metal sulfides by sulfate reducing bacteria. 

B. Venugopal and T. D. Luckey, Metal Toxicity in Mammals Chemical Toxicity of Metals and Metalloids, Vol. 2, Plenum Press, New York, 1978. 

There is concern over the toxicity of a nnmber of metals and metalloids, and their oxyanions. As for antibiotics, the genes for resistance are often plasmid-bome. There are several mechanisms that may operate—redaction, methylation, efflnx, and the synthesis of metal-binding metallothioneins. The following text illustrates aspects of these mechanisms. 

Methylation of both metals and metalloids has been observed for both fungi and bacteria. These metabolites may, however, be toxic to higher biota as a result of their volatility. The Minamata syndrome represents the classic example of the toxicity of forms of methylated Hg to man, even though the formation of Hg(CH3)2 was probably the result of both biotic and abiotic reactions. 

Metalls and metalloids are characterized by special ecochemical features. They are not biodegradable, but undergo a biochemical cycle during which transformations into more or less toxic species occur. They are accumulated by organisms and cause increased toxic effects in mammals and man after long term exposure [55]. 

Numerous commercial dyes are metal chelate complexes. These metals form pollutants which must be eliminated. One of the strongest points in favour of electrochemical reduction/removal of metal ions and metal complexes - the metal ions and weakly complexed ions form the toxic species - and of the metals from the metal-complex dye is that they are eliminated from the solution into the most favorable form as pure metal, either as films or powders. Polyvalent metals and metalloids can be transferred by reduction or oxidation treatment to one valency, or regenerated to the state before use, e.g. Ti(III)/Ti(IV), Sn(II)/Sn(IV), Ce(III)/Ce(IV), Cr(III)/Cr(VI), and can be recycled to the chemical process. Finally, they can be changed to a valence state better suited for separation, for instance, for accumulation on ion exchangers, etc. Parallel to the... 

Most of the surveys on metals and metalloids in food have concentrated on those elements that are known to be toxic, or where there are possible concerns about their levels in food. In the course of collecting the data, information on other metals is often collected in addition. Other metals that have been included in the UK Government s surveillance are zinc, antimony, chromium, cobalt, indium, nickel, thallium and tin. 

Twenty-three elements, including almost all the essential and toxic metals or metalloids such as As, Ag, Cd, Hg, Pd, and Tl, were quantified in 35 types of bottled and canned Polish beers by double-focusing SF-ICP-MS with ultrasonic nebulization after MW-assisted digestion of the samples [121]. Negligible levels... 

Human milk (or the substitute food, formula milk) is the only source of essential trace elements for newborns. To ensure the optimum development of the baby, mother s milk contains essential elements at the adequate levels. However, today it is well known that bioavailability, biological activity, nutritional value, as well as toxicity and metabolism of trace metals and metalloids strongly depend of their... 

Alkorta, L, Hernandez-Allica, J., Becerril, J.M., Amezaga, L, Albizu, L, and Garbisu, C. 2004. Recent findings on the phytoremediation of soils contaminated with environmentally toxic heavy metals and metalloids such as zinc, cadmium, lead, and arsenic. Reviews in Environmental Science and Bio/Technology, 3 71-90. 

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