Metal toxicity prevalence

Important questions to consider for metal toxicity are (1) Is the metal of concern toxic (2) What is the prevalence associated with the metal of concern (3) What are the signs and symptoms of exposure to that metal (4) Is the degree of exposure known (5) Do adequate analytical techniques exist to measure the metal (6) Are appropriate tissues available to quantify the metal ... 

Prevalence of Metal-Based Toxicity As the twenty-first century begins, one would expect that metal toxicities would be well known and avoidable. However, humans eiicmmter elemental toxins frequently, with chronic, low-concentration exposure occurring more frequently in individuals than in large population groups. 

The most commonly observed toxic reaction to nickel and nickel compounds in the general human population is nickel dermatitis and skin sensitivity arising from dermal contact with metals containing nickel (Sunderman 1970 NAS 1975 Norseth and Piscator 1979 USEPA 1980, 1986 WHO 1991 USPHS 1993). Studies on occupational dermatitis, which is the most prevalent... 

Willford, W.A. 1971. Heavy metals research in the Great Lakes, 1970-1971. Pages 53-65 in Prevalence and Effects of Toxic Metals in the Aquatic Environment. Proc. Univ. North Carolina, Rep. 57. 

Metals from the 6th period in Mendeleev s table are potentially the most toxic (Os, Ir, Pt, Au, Hg, Tl, Pb), however small water solubility of their prevalent salts decreases sharply this toxic influence (Table 1). 

In soil solutions, the kinetics of competition between ligands for certain metals (or vice versa) may be very important in controlling the prevalent form in solution and hence their availability or toxicity to plants. The formation of a metal... 

Metabolomics has made remarkable inroads into the environmental research community. Here, a major emphasis is to understand the impact that environmental stress, such as pollution and climate change, has on wildlife. Indeed, many government organizations monitor the prevalence of pollutants in certain species of wildlife as indicators of the exposure risk within the environment. Studies of Japanese medaka have been conducted to investigate the effects of trichloroethylene, a common environmental pollutant, and the pesticide dinoseb, on the development of fish embryos (44, 45). Similarly, cadmium toxicity has been examined in the bank vole and rat and has revealed changes in lipid metabolism that preceded classical nephrotoxicity (46, 47). Another study investigated the effects of environmental toxins on earthworms (48). In particular, the analysis of earthworm tissue extracts by NMR spectroscopy identified maltose as a potential biomarker for ecotoxicity within a metal-contaminated site. 

Dissolved As speciation is important in determining the extent of reaction with the solid phase and therefore the mobility of As in groundwater. Arsenic is generally present as arsenate [As(V)] or arsenite [As(III)] for Eh conditions prevalent in most groundwaters (Fig. 1). Arsenic metal rarely occurs, and the -3 oxidation state is found only in very reducing environments. Arsenite has been considered to be the more toxic oxidation state (U.S. Enviromnental Protection Agency, 1976) however, more recent studies have shown that most ingested As(V) can be reduced to As(III). 

The prevalence of toxic metal ions in contaminated aqueous and terrestrial environments represents a significant environmental risk. Effective pollution con-... 

For most purposes, the important ions in soil chemistry are those that are essential, or toxic, to living organisms. Although opportunistic, evolution took little or no advantage of the most prevalent ions—O, Si, Al, Ti, Na, and Q—in soils and oceans. Figure 2.1 shows the essential ions in bold type, and the toxic ions are cross-hatched. The soil is both the source of the essential elements and the safest disposal site to return the elements back to their native biogeochemical cycles. The elements arc present as ions in nature because the zero oxidation state is unstable for most elements. The exceptions are O2, N2, the inert gases, and the precious metals Au, Pi, Ag, and so on. In the elemental state atoms bind only to each other. As ions, the elements are active and react with other ions. 

Metallic mercury is relatively benign compared to the cilkyl compounds of mercury, which are mainly nervous system poisons. Methylmercury is the most potent of these and also the most prevalent because of its presence in fish. It now is known that microorganisms in the bottom sediment of lakes cind rivers convert inorganic mercury into the more toxic methyl form. Taken up by plants and plankton, it ascends the food chain to humans. Predatory marine fish, such as tuna and swordfish, also contain sub-stantied levels. Although most of our knowledge of human toxicity... 

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