A Toxic Element

Beryllium is a toxic element, and the reduction operation is therefore carried out in a well-ventilated special double enclosure. The furnace controls are located outside the enclosure. The ball milling of the reduced mass is carried out in walk in-type fume hoods. 

Lead is also used in organ pipes, of course. Other uses include the lead-acid battery, radiation shielding, ceramic glazes, and in lead glass. It is a toxic element, and its organic derivatives are also toxic. Tetraethyllead was used for many years as an anti-knock agent in petrol. 

The view at Cadmium changed with time starting from a valuable resource and ending up as a toxic element with a limited number of applications not substituted by alternative products. The decontamination of the technosphere works to a certain extent. Due to the character of Cd as trace contamination of phosphate fertilizers and of Zn ores and fossil fuels, there is no final solution for the environmental contamination. Due to the restrictions issued in many countries, there is reason to fear that Cd could end up in unknown material streams. From an analysis of the refining of Zn ores in 2002, it has been concluded that about one quarter of Cd generated as by-product ( 7,000-8,000 Mg) could not be found either in the products analyzed or in the emissions from the process [27]. 

Parsons et al.66 reported on the determination of total mercury as a toxic element in urine at the trace level using ICP-MS. The main sources of exposure in the human body are inhalation of Hg vapour released from dental amalgams and the consumption of fish species that accumulate, for example, methyl mercury (MeHg). 

Size exclusion chromatography coupled to an ICP-QMS with an octopole collision cell was employed for the multi-elemental speciation of essential elements (P, S, Cr, Mn, Fe, Co, Cu, Zn, Br, Se and I) and Al as a toxic element in premature human milk.28 Comparison of speciation results demonstrates that premature human mothers milk differs significantly from formula milks in terms of the element binding pattern to the biomolecules. It was found that premature human milk is very rich in high molecular weight species associated with metals. The authors concluded that more attention must be paid to the chemical form in which essential elements are added to the formulas, particularly those used for the nutrition of premature babies.28... 

It is somewhat difficult to define what is meant by a toxic element. Some elements, such as white phosphorus, chlorine, and mercury, are quite toxic in the elemental state. Others, such as carbon, nitrogen, and oxygen, are harmless as usually encountered in their normal elemental forms. But, with the exception of those noble gases that do not combine chemically, all elements can form toxic compounds. A prime example is hydrogen cyanide. This extremely toxic compound is formed from three elements that are nontoxic in the uncombined form, and produce compounds that are essential constituents of living matter, but when bonded together in the simple HCN molecule constitute a deadly substance. 

Why is it difficult to define what is meant by a toxic element What are the major categories of toxic elements Give an example of each. 

The presence of yeast in beverages, as happens with certain wines, may contribute to the potential incorporation of Hg, a toxic element for humans. Capelo and coworkers [80] developed and investigated the performance of two different reactors for sample ozonization as a previous step to Hg determination in white wines by FI A combined with cold vapor (CV) A AS. The pretreatment with 03 allowed the drastic reduction of the amount of chemical reagents used in the FIA-CV-AAS system. An LoD of 0.5 p,g l-1 was obtained and the Hg content in four analyzed wines varied from 94 + 9 to 101 + 5 jig 1 1-... 

Cr(VI) is a toxic element, and its environmental pollution should be monitored even in seawater. CrO - is a stable chemical species in seawater, while Cr(III) also exists in relatively high amounts. Therefore, a separation of Cr(VI) from Cr(III) is necessary in the analysis of Cr( VI). For this purpose, the solvent extraction technique can also be used, being followed by atomic absorption analysis. Many workers have investigated the solvent extraction of total Cr in seawater, where Cr was extracted with acetylacetonate, DDC, APDC and analysed by AAS [37—42]. Hiiro et al. examined in detail the separation of Cr(VI) from Cr(III) in seawater [42]. The effect of pH values on extraction of Cr(VI) is shown in Fig. 5. Cr( VI) is most effectively extracted near pH 5, while Cr(III) is increasingly extracted above pH 4. Therefore,... 

The listed species can be dissolved in different solvents. Depending on the composition and aim of the studies (e.g., the study of the speciation of a toxic element), different solvents and procedures can be used for sequential extraction (e.g., see Lakanen and Ervio 1971 McGrath 1996). 

Sulphur is not generally considered as a toxic element in the same way as are the halogens. Nevertheless, its presence seems to confer on a substance the capability of penetrating the... 

There are several reasons why it is difficult to establish the essentiahty of trace elements. Some elements, such as arsenic and selenium, were first recognized for their extreme toxicity, so it has been difficult to convince many health specialists that a toxic element might also be a dietary essential at low levels. Also, most trace elements are present in extremely small amounts in diets and in tissues, and few laboratories are equipped to prevent contamination of samples and to measure these elements with the necessary precision. 

Selenium is generally considered a toxic element. (It is the active component of QUESTION 1 0.6... 

Beryllium is a toxic element, even when present in compounds or alloys. For example, beryllium oxide is a finely powdered compound that, when inhaled, can lead to a painful and deadly disease called berylliosis. 

Some elements have incorrectly been labeled as all good or all bad. Oxygen at 20 volume percent O2 in air is necessary for aerobic organisms but is deadly to anaerobes. Concentrated, 100%, O2 is helpful for humans to breathe only for a short time longer periods are harmful. Arsenic is known as a toxic element, but low As concentrations are essential to living organisms. 

Lead is considered to be a toxic element as a consequence of a variety of biochemical effects. Among these are included neurological problems, haematological effects, renal dysfunction, hypertension and cancer (the lARC has classified Pb as a carcinogen), for which there is evidence in animals but not yet in humans. The latter study, also involving humans, however suggested that the increases in lead uptake have occurred when dietary Fe was low. 

The order of addition of an organic ligand and a toxic element in anionic form to a sorbent strongly affected the adsorption of the pollutant as well. The adsorption of As on ferrihydrite at pH 4.0 when As and MAT were added as a mixture (MAT+As) or when MAT was added before As (MAT before As) (initial MAL/As molar ratio ranging from 0 to 1) is shown in Fig. 11. At an initial MAT/As molar ratio of 1, the inhibition of MAT was about 1% when the ligands were added together and 22% when MAT was added before As. When As was added before MAT (As before MAT), the inhibition of MAT to prevent As adsorption was negligible (data not shown). 

As mentioned in Section 20.3.2.2, arsenic is a toxic element that occurs naturally in soils, rocks, and groundwater. It enters drinking water supplies from natural deposits in the Earth or from agricultural and industrial practices. Long-term drinking water exposure can cause serious health problems such as skin, lung, bladder, and kidney cancer. The U.S. EPA has set the arsenic standard for drinking water at 10 parts per billion (10 p-g/L), which has been effective since January 2006 (66). 

The removal of solvated cadmium ions (Cd ) from water has been studied because ionic cadmium is a toxic element (itai-itm disease in Japan) and one of the main metallic pollutants of industrial aqueous effluents (electrodeposition, Ni-Cd batteries etc.). When alumina-deposited nickel, previously reduced under a hydrogen flow, is suspended in a Cd solution, a quick and strong decrease in pH is observed, followed by a slow pH increase with time. The pH decrease has been interpreted by the reaction ... 

There is an abundant literature on the biochemistry of Cd as a toxic element in a variety of organisms from bacteria to humans. Like all other reactive trace metals, Cd can be toxic simply because of unspecific reactions with protein ligands. For example, reaction of Cd with cysteine thiol groups, for which it has a great affinity, can denature enzymes and make them inactive. More specific toxic effects of Cd result from blockage of certain physiological functions when Cd substitutes for other metals, Ca or Zn, in particular. The ionic radius of Cd and Ca are very similar and cadmium can interfere with Ca metabolism or replace Ca in structural functions [30,31]. 

Lewisite (a-lewisite or 2-chlorovinyl dichloroarsine) is only slightly soluble in water but when dissolved it hydrolyses rapidly into 2-chlorovinylarsine oxide. The oxide is fairly soluble in sea water. In an alkali solution a further reaction into acetylene and arsenic acid might be possible. With high turbulence, lewisite can dissolve more rapidly in large volumes of water. Because lewisite is 36 per cent arsenic by weight, even if broken down, a toxic element would always remain. 

O2 has two opposing effects on photoinhibition. It can reduce the photoinhibition by photorespiration through which the excess energy is partly dissipated (10) it can also increase the photoinhibition as a toxic element which damages the photosynthetic apparatus (1). In a CO2-... 

Processes with releases of elements and slowly degrading compounds distribute hazardous pollution into the environment with the prospect of constandy cycling effects as the pollution continuously transfers through environmental media. As the chlor-alkah example shows, a toxic element can dominate PEI when the effects are calculated over a long time period. What the example did not show is the effect of a second year of releases on the results, or for that matter 10, 20, or 50 years of nondegrading pollution. Without doing further calculations, it is clear that mercury impacts will stack on top of each other year after year, while compounds that (rapidly) degrade have efiects that remain relatively low. 

The analysis shown for the chlor-alkali process did not consider the input of mercury or its upstream supply chain. Mercury was not considered as an input in the chlor-alkah example, but it should have been had the analysis been able to consider all inputs. In addition, any time a toxic element, Hke mercury, is used in a process it must be generated in upstream processes. Based on a Hfe cycle perspective of this supply chain, it is Hkely that mercury would dominate the long-term toxicity evaluated over decades, or for that matter over much shorter time periods. 

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