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Canned foods, metal uptake

Despite the quantitative variability of salts and silicate dust particles in the plants of Arid ecosystems, we can easily discern a trend towards the selective uptake of trace elements. The calculation of coefficient of biogeochemical uptake (Cb) shows the rates of exposure to heavy metals in biogeochemical food webs. One can see that the elements contained in the plant species of both Steppe and Desert ecosystems are in equal measure susceptible to the influence of environmental factors. The most extensively absorbed are Sr, Cu, Mo, and Zn. Their values of Cb are more than unit. The group of other elements, like Ti, Zr, and V, are poorly taken up, with their values of Cb often dropping below 0.1 (see Figures 4 and 5). [Pg.177]

Trace elements on the surfaces of fly ash particles that are accessible to humans through air, soil, water, can affect health in several ways. The pathways by which metals from CCP may cause harm include (1) soil deposition and resulting plant uptake of metals and subsequent movement into the food chain (2) direct ingestion of soil by animals or humans (3) leaching of metals from CCP to water systems and uptake by plants, animals, or humans and (4) inhalation of dust (from soil) or respirable ash particles (Ryan Bryndzia 1997). [Pg.241]

Aluminium is the third most abundant element in the earth s crust and is used widely in the manufacture of construction materials, wiring, packaging materials and cookware. The metal and its compounds are used in the paper, glass and textile industries as well as in food additives. Despite the abundance of the metal, its chemical nature effectively excludes it from normal metabolic processes. This is due largely to the low solubility of aluminium silicates, phosphates and oxides that result in the aluminium being chemically unavailable. However, it can cause toxic effects when there are raised concentrations of aluminium in water used for renal dialysis. These effects are not seen when aluminium is at the concentrations usually present in drinking water. There is currently much activity to examine the factors that influence uptake of aluminium from the diet. [Pg.159]

The assessment of plant-available soil contents can frequently be achieved and validated by field experiments for nutritionally essential elements, and, for a few potentially toxic elements such as chromium, nickel and molybdenum, at the moderately elevated concentrations that can occur in agricultural situations. The validation of extraction methods, devised for agricultural and nutritional purposes, is much less easy to achieve when they are applied to heavy metals and other potentially toxic elements, especially at the higher concentrations obtained in industrially contaminated land. This is not surprising in view of the fact that for some heavy metals, for example lead, there is an effective root barrier, in many food crop plants, to their uptake and much of the metal enters plants not from the root but by deposition from the atmosphere on to leaves. In these circumstances little direct correlation would be expected between soil extractable contents and plant contents. For heavy metals and other potentially toxic elements, therefore, extraction methods are mainly of value for the assessment of the mobile and potentially mobile species rather than plant-available species. This assessment of mobile species contents may well, however, indicate the risk of plant availability in changing environmental conditions or changes in land use. [Pg.266]

Effects of l.ead tPbi it is one out of four metals that have the most dangerous effects on living organisms. It can enter the human body via air, water and in most of all through uptake via food. In humans Pb can be associated with kidney and brain damages, a rise in blood pressure, disruptive child behaviour and learning abilities etc. [Pg.359]

Understanding the distribution of chemical forms of metals within certain water types, and their uptake into biota, is based on the electronic configuration of elements and the empirical classification of electron acceptors (metals) and donors (ligands) to hard and soff categories (Morgan and Stumm 1991, Raspor 1991). The relationship between the chemical properties of elements, and their uptake and accumulation - which has implications on detoxification and food chain transfer - will be considered. Classification of trace metals as either essential (Fe, Cu, Mn, Zn, Co) or non-essential (Hg, Cd, Ag, Pb) should be performed with caution, bearing in mind that the former can exert beneficial effects at low concentrations and harmful ones at higher levels. [Pg.129]

The toxic effects of arsenic can be counteracted with (1) saline purgatives, (2) various demulcents that coat irritated gastrointestinal mucous membranes, (3) sodium thiosulfate, and (4) mono- and dithiol-containing compounds and 2,3-dimercaptopropanol. Arsenic uptake in rabbit intestine is inhibited by phosphate, casein, and various metal-chelating agents. Mice and rabbits are significantly protected against sodium arsenite intoxication by A-(2,3-dimercaptopropyl)phthalamidic acid. Conversely, the toxic effects of arsenite are potentiated by excess dithiols, cadmium, and lead, as evidenced by reduced food efficiency and disrupted blood chemistry in rodents. [Pg.24]


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See also in sourсe #XX -- [ Pg.223 ]




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