Non-Essential Elements

These elements are sometimes called toxic elements. Although many elements belong to this group, a few only are encountered in the clinical or occupational laboratory. This is also reflected in the literature. For this reason only the most common elements are mentioned. 

The most common method used to monitor inorganic Pb is the determination of Pb in whole blood by GF-AAS. Exposure to organic lead (i.e. tetraethyl lead) can be monitored by the determination of Pb in mine by GF-AAS (Christensen and Kristiansen 1994). Early effects of exposure to Pb on the heme synthesis can be monitored by determination of the inhibition of the enayme 8-aminolevulinic acid dehydratase in whole blood or 8-aminolevulinic acid in urine by spectrophotometry. 

Acute exposure to cadmium may lead to chemical pneumonitis and edema, but is rare nowadays (Herber 1994b). Chronic exposure to Cd affects mostly the renal tubules and the lung. Exposure to Cd can take place both in the occupational and environmental area. 

Since the 1980 s occupational and environmental exposure to Cd has been reduced due to banning of Cd in pigments, plastic softeners, fertilizers, and batteries. In some European countries (e.g. Sweden) Cd has been banned completely. 

Monitoring of Cd exposure can take place by the determination of Cd in whole blood (reflects recent exposure) or urine (reflects body burden) by GF-AAS. Early effects can be monitored by the determination of a tubular protein (e.g. 132-microglobulin, retinol binding protein, a2-microglobulin) or the activity of an enzyme (e.g. N-acetyl 3-D-glucosaminidase) in urine. 

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Narrow project scope Perhaps non-essential elements of the project can be eliminated, thereby reducing costs and/or saving time. X X... 

Tab. 6.3 RMs for essential electrolytes (i), essential and therapeutically used trace elements (2) and non-essential elements (3)...

We conclude this idiosyncratic trip through the Periodic Table with four non-essential elements. Platinum, initially in the form of cisplatin, has been hugely successful in the... 

A. A. Momen, G. A. Zachariadis, A. N. Anthemidis and J. A. Stratis, Use of fractional factorial design for optimisation of digestion procedures followed by multielement determination of essential and non-essential elements in nuts using ICP-OES technique, Talanta, 71(1), 2007, 443 51. 

Fig. 1. Metabolic activity vs. concentration for essential and non-essential elements reprinted from Wood and Wang, 1983.

Meador, J.P., D.W. Ernest, and A.N. Kagley. 2005. A comparison of the non-essential elements cadmium, mercury, and lead found in fish and sediment from Alaska and California. Sci. Total Environ. 339 189-205. 

In drawing up a WBS care has to be taken not to make it just a long hierarchical fist of things to do, including non-essential elements, so that the process becomes extended in time, which defeats the object. 

These theoretical frameworks were selected for formal integration and explanation , making no assumptions other than the ability of living beings to reproduce and that some chemical features of (biocatalytically) essential can be pinpointed which distinguish them from non-essential elements. Explanation here means reduction to some theoretical framework in quantitative terms also, that is, constructing a model which can account for the observed effects vs. exclusion of others which are not observed, e.g., non-essentiality of some other elements owing to a semi-empirical description of their chemical properties. 

The behavior of some reproducing system will change in the very moment when a former resource turns into a sink for the same - essential or non-essential - element, e.g. by biogeochemical changes in the area. In either case further existence or at least the ability of the species/population to keep on reproducing are jeopardized. Effects in population structure can be anticipated even if aU the individual organisms survive at first. 

As anticipated, some non-essential elements may respond to biological redox gradients in a quite similar manner as Fe does because there need not be any direct transformation during photosynthesis europium which both undergoes ready, high-quantum yield photoreductions when irradiated (X > 340 nm) together with alcohols, sugars or amino acids (Horvath and Stevenson 1992, see below), and the redox potential of... 

When Ti = 1, the heavy metal content does not affect the plant growth. For Ti < 1 and Ti > 1 respectively, favourable and phytotoxic effects are observed. For essential elements, the concentration in the plant tissue is limited by a lower critical level, indicative for deficiency and by an upper critical level, indicative for toxicity. Non-essential elements are only showing the latter. 

An essential element, zinc (Zn), and a non-essential element, cadmium (( d),... 

In addition, the sensitivity/tolerance of wild medicinal plants to essential and non-essential elements need to be established. A recent stndy indicated that the maximnm permissible concentrations for trace elements and heavy metals in Sonth African agricnltnral soils may be too high for the growing of wild medicinal plants (26). 

Many substances that might be considered toxic are in fact essential to life, for example the heavy metals Co, Cu, Fe, Se, Zn. Thus, there is a relationship between concentration of the substance and the health response it invokes. An element is essential to life when a deficient intake of the element consistently results in impairment of a life function from optimal to suboptimal (Fig. 1a). Moreover, when physiological levels of this element, but not of others, are supplemented or restored, the impairment is cured and optimal health is restored (Fig. 1a). By contrast, non-essential elements do not produce a positive health response. An organism may tolerate low concentrations of some non-essential elements (Fig. 1b). Even dangerous poisons such as arsenic oxide (As203) can be tolerated... 

The average amounts of some essential and non-essential elements in the human body are shown in Table 2.1. This shows that the weights of some of the essential elements in the body vary by six or more orders of magnitude. Oxygen, at 45 kg, is by far the most abundant element with the majority being present as one simple inorganic compound water. Some of the elements listed in Table 2.1, and marked with an asterisk, have no known beneficial function and are present in the body simply because they are present in rocks and soils and find their way into water and foodstuffs and from thence into the human body many of these elements are present in only minute quantities. 

Levels of essential and non-essential elements in cows whole milk... 

Table 3 Mean concentration of essential and non essential elements in cows whole milk samples collected in two sampling periods (n = 3)...

WosHNER VM, O Hara TM, Bratton GR, Suydam RS and Beasley VR (2001) Concentrations and interactions of selected essential and non-essential elements in bowhead and bduga whales of arctic Alaska. J Wildlife Dis 37 693-710. 

Yttrium is a non-essential element for microorganisms, plants, animals, and humans. However, no adverse effects of yttrium have been reported on plants and microorganisms, nor has any mechanism of yttrium detoxification in mammals been identified (Luckey and Venugopal 1978 Deuber and Heim 1991). 

Future trends in trace element analysis will put even greater pressure on the need to provide unbiased determinations. Increasing interest in the role of trace elements in health and disease will provide the stimulus for the better provision of quantitative determinations on which important decisions are made (Centers for Disease Control, 1991 Moukarzel et al., 1992). Increased public awareness and legislation are likely to bring about substantial reductions in the currently acceptable levels of occupational and environmental exposure to some non-essential elements such as lead, cadmium and aluminium. Determinations that are made as part of the assessment of such exposure will need to be both carefully validated and reproducible over many years or decades (Braithwaite and Brown, 1988 Brown, 1991), which will have a serious impact on laboratory costs. However, reproducible trace element determination with a low bias in biological fluids represents the cornerstone of any proper understanding of the role of trace elements in human health and disease. 

Both macro- and micro-elements are nutrients that are necessary for the growth and normal development of organisms and whose function cannot be taken on by any other element. They are therefore termed essential . For this reason, macro- and microelements are also called macro- or micro-nutrients. A division into essential and non-essential elements is not always appropriate, since there are numerous exceptions that become apparent when, for example, higher and lower plants are compared. We now know that calcium, boron and chlorine are not essential to some bacteria and fungi, and that sodium and silicon are not essential to higher plants (Marschner, 1983). 

Like the division into essential and non-essential elements, the above classic division into micro- and macro-elements that is based solely on the physical mass of an element within an organism has undergone considerable modification in modern plant, animal and human physiology. Additions have had to be made to the list of macroelements for certain groups of organisms. For example, the element silicon must be regarded as a macro-element for horsetails and diatoms. Moreover, conditions at particular sites often lead to element-specific or organism-specific accumulation... 

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