Toxic mineral element

In addition to toxic mineral elements, some anions exhibit toxic effects on the human organism even if ingested in low concentrations. Legislation only specifies the maximum levels for nitrates and nitrites. Other anions, however, may also have toxic effects, such as... 

Inorganic mineral elements that have a function in the body must be provided in the diet. When insufficient, deficiency symptoms may arise, and if present in excess they may be toxic. 

Multi-element trace analysis is an important prerequisite for the quality assurance of foodstuffs with respect to the characterization of non-essential, toxic and essential (nutrient) elements as pollutions or as mineral elements relevant to health. Contamination with heavy metals such as Cd, Pb or Hg has become a serious problem with increasing environmental (artificial) contamination e.g., due to industrial pollution. The increasing use of inorganic mass spectrometric techniques (especially of ICP-MS) in the analysis of foodstuffs for multi-element analysis of trace elements or the detection of selected elements and species at a low concentration level has resulted from advances in very sensitive and quantitative measurements of metals, metalloids and several non-metals, including their speciation. 

Preliminary studies have shown that it is possible to remove over half of the potentially toxic trace elements present in coal when the mineral matter is reduced by coal washing. When coal is burned in a power plant, about 13% of the mercury and about 50% of the lead and cadmium may remain with the fly ash. Analytical chemical techniques have been developed to determine Hg, Cu, Cr, Mn, Ni, Cd, Pb, and F in coal and fly ash. These techniques produce accurate and precise results despite the fact that there are no coals with established trace element content, except for mercury. 

Of the seven macro mineral elements required by dairy cattle, five can be considered fertilizer elements (potassium, calcium, phosphorus, magnesium, and sulfur), but sodium and chloride are both toxic lo plants at high concentrations and present practical problems in areas with saline soils. High salt intakes have also been shown lo increase udder edema in heifers. Because of the importance of chloride in nutrition and mclabolisni. research is needed to define the chloride requirements of lactating cows and clarify mineral relationships, especially between chloride and potassium plus sodium-... 

Phosphorus is an essential mineral element. Phosphorus homeostasis in the body is controlled by hormonal and renal control systems. Phosphorus intoxication from excessive consumption in food is not known. Toxic exposures have been reported to occur from its industrial use or from suicidal ingestion of phosphorus-containing materials. Phosphorus is highly toxic to humans and animals. The acute lethal dose in humans is lmgkg . ... 

Data concerning the toxicity of the four discussed toxic minerals are presented in Tables 4.5 and 4.6. The uptake of elements is not entirely independent of one another. Elements of similar chemical properties tend to be taken up together. Sometimes one element has an inhibiting effect on another, or there can be a synergistic effect, e.g., enhancement of absorption of calcium in the presence of adequate amounts of phosphorus, or cadmium and lead hindering calcium and iron absorption, or zinc and copper antagonism and their influence on the ratio of Zn/Cu on copper deficiency. 

Three-quarters of the metal minerals are processed and mostly consumed in the relatively small highly industrialized countries which contain one-quarter of the world s population. The aerial concentration of processing and consumption causes environmental problems, and the risk of contaminating soils, rivers and air with toxic trace elements is high in industrialized countries. Beside the firing of coal and oil, processing of ores and the technical use of several metals is a major source of such contamination. 

The many mineral interactions which influence the safe dietary levels of essential and toxic elements are partly represented in Figure 3.2. While interactions involving dietary elements may be either detrimental or beneficial, the major concern is that an antagonistic element may induce a deficiency of its counterpart nutrient whose concentration in the diet is borderline. The assessment of such in-vivo interactions will be considered here under the limits of bioavailability, which occurs at the site of absorption in the intestinal mucosa or the redistribution from one tissue to another one. Figure 3.2 illustrates the most important, quite different, species-specific interactions of metals, trace and macro elements, respectively, with net requirements in animals and man. Clearly, there are interrelationships in the metabolism of the mineral elements consumed. 

The toxic effects of the mineral elements are extremely element- and species-specific (Hapke 1991). The symptoms of acute poisoning (Geldmacher von Mallinckrodt 1991a) and chronic toxicity of inorganic elements can be completely different (Ewers and Schlipkoter 1991). The most common symptoms of acute metal poisoning include the following ... 

The three-dimensional structure of the domains showing the localization of the metal ions is shown in Figure 6.2. The elevated content of -SH groups allows the binding of mineral elements and of toxic heavy metals that are commonly present in situations of environmental pollution, and which are also accumulated in human and... 

What are the reported bad effects of nitrification The more important are (1) the greatly increased leachability of nitrites and nitrates in comparison with ammonia (2) the instability and reactivity of nitrites which may lead to volatile losses of nitrogen (3) the increase in soil acidity as a result of nitrate formation, especially where the nitrates are lost by leaching. With increase in acidity there may be toxic effects on plants produced by nitrites and aluminum and also excessive loss of mineral elements. 

This general lack of interest in the chemistry of the mineral constituents is unfortunate in view of the increasing recognition of the importance of the minerals in conversion as well as the toxicity of some trace elements, especially the heavier metals. On this latter aspect, it is worthy of note that there is a high potential for the recovery of valuable mineral elements from coal conversion processes as added-value products in addition to their removal from the system prior to the onset of adverse effects on the environment. 

The transition elements are useful tracers in many geological systems. They are industrially important and form economic ores, especially in hydrothermal systems where they are often present as sulfide minerals. Cd, Hg, Zn, and Pb are persistent industrial pollutants and determination of low levels of these elements in ores and fossil fuels is critical as processing of ores or burning of fuels may concentrate and release toxic elements. The concentration of such toxic trace elements may affect the economic value of an ore or fossil fuel deposit significantly. 

Isotope dilution mass spectrometry is an accurate and sensitive technique for determining toxic trace elements in food matrices. Lead, cadmium, and thallium have been analyzed rapidly down to very low levels by ICP-MS. The latter technique is particularly useful for simultaneous measurement of a wide range of elements. Because the toxicity of an element can be highly dependent on its chemical form, ICP-MS is also useful in the speciation of toxic minerals in foodstuffs by combination with HPLC or SEC. 

Why does the solubility of a salt of a basic anion increase with decreasing pH Write chemical reactions for the minerals galena (PbS) and cerussite (PbC03) to explain how acid rain mobilizes trace quantities of toxic metallic elements from relatively inert forms into the environment, where the metals can be taken up by plants and animals. Why are the minerals kaolinite and bauxite in Box 12-1 more soluble in acidic solution than in neutral solution ... 

An area of research where effort is currently being directed is the study of metal complexation in aqueous solutions and on mineral surfaces (see Hochella and White 1990 and references therein). The reason that research is focusing on details of the molecular structure in this type of system is that scientists have begun to realize that speciation can play a dramatic role in the mobility and toxicity of elements in the environment (see Brown et al. 1999 for a review). Molecular modeling has the potential to make an impact on this field in a variety of ways (see Rosso, Rustad or Sherman, this volume), one of which is in modeling vibrational spectra to help interpret observed spectra. When model vibrational frequencies can be combined with model NMR chemical shifts (see Tossell, this volume) and compared with experimental spectra, complex problems may be more easily understood. 

The concentration and/or activity of dissolved Fe(III) is thus controlled by different mineral phases depending on the pH. This is illustrated in Fig. 3, which plots the pH-dependent variation in the concentration and speciation of dissolved iron in different mine pit lakes of the IPB. Among the 15 pit lakes studied, jarosite was only observed to precipitate in Corta Atalaya, so that this mineral controls the apparent equilibrium which seems to exist between dissolved and particulate Fe(ni) in this lake. Conversely, ferrihydrite is the mineral form under which Fe(III) precipitates in Los Frailes pit lake. Most lakes, however, seem to be at or near equilibrium with respect to schwertmannite, which not only controls the solubility of Fe(III), but also buffers the systems at pH 2.5-3.5 (through reaction (5)), and sorbs toxic trace elements like As [5-14, 24—28]. 

As discussed below, the formation of this mineral during neutralization can also imply a significant removal of toxic trace elements (e.g., Cu, Zn, Cr, U) from the aqueous phase. 

Many food constituents are potentially toxic to the animal consuming them. Microbial contaminants are an obvious example the digestive enzymes kill many bacteria, but some organisms may damage the gut, which allows them or the toxins they produce to invade the animal s tissues. Foreign proteins, especially those with endocrine activity, could harm the animal if absorbed, but the gut provides an effective barrier to prevent their absorption before they are hydrolysed. The same is true of nucleic acids (whose breakdown is a matter of concern, as some animal foods may now be derived from genetically modified plants). Some of the toxic constituents of pasture plants are broken down in the rumen of cattle, sheep and goats (see p. 494). As mentioned above, the animal body avoids excessive intake of the mineral elements calcium and iron by selective absorption. 

Fluorine is another potentially-toxic trace element which is dispersed by atmospheric pollution and it has long been recognised that damage to plants occurs and that there is a hazard to man and farm stock, in the vicinity of industrial plants processing fluoride-containing minerals. Such plants include factories for the production of aluminium, superphosphates and compound fertilisers based on the liberation of phosphoric acid from rock phosphate. In October 1976, ten cows had to be destroyed on two farms in the vicinity of the British Aluminium Company s aluminium smelter at Invergorden in the north of Scotland, and problems of fluoride toxicity have been commonly associated elsewhere with the production of aluminium. 

Mineral imbalances and toxicities— There is still considerable controversy regarding the optimal amounts of various essential mineral elements because dietary excesses of certain elements may interfere with the utilization of others. Eur-thermore, almost every one of the nutritionally essential minerals has potential toxicity at high levels. However, these toxicities are not as likely to result from eating unfortified foods, as they are from special circumstances such as (1) the taking of mineral supplements (2) contamination of food and water by environmental factors such as containers, piping, and airborne dusts and/or (3) fortification of foods with minerals. 

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