Elements, essential toxic

IAEA -- Detection limits needed for trace elements [essential, toxic] in bioenvlronmental matrices. [Coordinated Research Programs]... 

Health and Environment. Manganese in trace amounts is an essential element for both plants and animals and is among the trace elements least toxic to mammals including humans. Exposure to abnormally high concentrations of manganese, particulady in the form of dust and fumes, is, however, known to have resulted in adverse effects to humans (36,37) (see Mineral nutrients). 

The bad guys, shown in pink in Figure 2.8, are toxic, often lethal, even in relatively small quantities. Several of the essential trace elements become toxic if their concentrations in the body increase. Selenium is a case in point. You need about 0.00005 g/day to maintain good health, but 0.001 g/day can be deadly. That s a good thing to keep in mind if you re taking selenium supplements. 

Ecologically, copper is a trace element essential to many plants and animals. However, high levels of copper in soil can be directly toxic to certain soil microorganisms and can disrupt important microbial processes in soil, such as nitrogen and phosphorus cycling. Copper is typically found in the environment as a solid metal in soils and soil sediment in surface water. There is no evidence that biotransformation processes have a significant bearing on the fate and transport of copper in water. 

Inorganic or metal-containing medicinal compounds may contain either (a) chemical elements essential to life forms—iron salts used in the treatment of anemia—or (b) nonessential/toxic elements that carry out specific medicinal purposes—platinum-containing compounds as antitumor agents or technetium... 

The success of such approaches critically depends on our ability to identify the essential mechanistic elements of toxicity pathways and to rebuild them in in vitro models, and on the possibility to conclude about cause and effect relationships between human exposures and diseases. Both these aspects provide significant challenges for research. 

The investigation of body fluids with respect to nutrient (essential) elements and toxic elements -which are challenging topics for analytical chemistry - include the determination of concentrations at the trace and ultratrace level. However, isotope variation and isotope effects (especially of lighter elements such as hydrogen, carbon, nitrogen, oxygen but also of iron and calcium) have also been studied.22 23 The most frequently applied mass spectrometric technique for the analysis of body fluids today, which fulfils all requirements and also results in accurate and precise data, is ICP-MS. 

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. 

Selenium is a trace element essential to life. For example, the selenium-containing enzyme glutathione peroxidase catalyzes the destruction of peroxides (ROOH) that are harmful to cells. Conversely, at high concentration, selenium can be toxic. 

In Chapter 10 elements were discussed that as a rule tend to be toxic in their various forms. Chapter 11 covers toxic inorganic compounds of elements that are not themselves generally regarded as toxic. These elements include for the most part the lighter nonmetals located in the upper right of the periodic table (Figure 1.3) and exclude the heavy metals. Most of the elements involved in the inorganic compounds discussed in this chapter are those that are essential for life processes. Any division between toxic and nontoxic elements is by nature artificial in that most of the heavy metals have compounds of relatively low toxicity, and there are deadly compounds that contain elements essential for life. 

One of the elements essential for life, sulfur is a constituent of several of the more important toxic inorganic compounds. The common elemental form of yellow crystalline or powdered sulfur, S8, has a low toxicity, although chronic inhalation of it can irritate mucous membranes. 

Coal contains most of the elements of the periodic table, the majority of which are present in concentrations of 100 ppm or less. Many of these trace elements are toxic to plant and animal life, even at low levels. Because U.S. power plants consune on the order of 600 million tons of coal annually for the production of electricity (1), coal combustion can mobilize thousands of tons of potentially hazardous trace elements into the environment each year. Due to the large quantities of coal combusted, even trace amounts of toxic elements present in the coals can accumulate to hazardous levels. Also, potentially deleterious effects of particulate emissions from coal combustion may be enhanced since many trace elements are surface-enriched (2) and concentrate preferentially in the smaller, more respirable particle sizes (3). Substantial amounts of some elements, such as As, Hg, and Se, are in the vapor phase in flue gases from coal combustion and are essentially unaffected by most particle control devices. Aside from the potential detrimental environmental aspects, trace elements in coal can pose adverse technological... 

Selenium occurs in the earth s crust as metal selenides [5], and the element and its compounds are used in electronic applications and in the production of glass, ceramics, and stainless steel [11]. In trace amounts, selenium is an essential nutrient, but in higher quantities or when certain species are present, the element becomes toxic. The most important forms of selenium are selenate (Se042-), and selenite (Se032""), and selenide (Se2 ). Selanates are relatively soluble, whereas selenites and elemental selenium are virtually insoluble [12]. 

Elemental analysis of body tissues and fluids by atomic absorption spectrometry with electrothermal atomisation has advanced significantly the understanding of the role of trace elements in clinical biochemistry. All of those aspects of metabolic processes that are affected by changes in the concentrations of accessible trace elements have been studied. These include deficiencies of essential trace elements as a result of inherited or acquired metabolic disorders, or from nutritional inadequacy and excesses of trace elements producing toxicity states as a result of inherited metabolic disorders involving essential trace elements or from the inappropriate exposure to, or ingestion of, non-essential trace elements. 

CONCENTRATIONS OF NON-ESSENTIAL, TOXIC TRACE ELEMENTS IN BODY TISSUES AND FLUIDS... 

Metal ion toxicity does not relate to essentiality. Toxicity and essentiality do share, however, one feature frequent interdependencies among metal ions, between metal ions and nonmetals, and between both, and organic molecules such as vitamins. For example, excess Zn + may reduce absorption of essential Cu +, while a deficiency of Zn + worsens Cd + toxicity. Such antagonisms and mutual dependencies produce variable toxicities for like concentrations of an element. 

Fluorine Probably essential element Moderately toxic, may cause Pollution by fluoride present... 

Selenium is both a toxic and an essential element. The toxicity depends greatly on the species. Selenium is a cumulative toxic substance and can be a serious health hazard when present in high concentrations in food and water. However, at very low levels, pg/kg it is recognized as an essential trace element in animal nutrition. 

Fertile soils supply plants with all of the trace elements essential for growth, believed at the present time to be Fe, Mn, Zn, B, Cu, Mo, and CL These seven elements are called the micronutrients, a term that indicates the small quantities needed by plants but not necessarily the concentrations found in soils. Deficiencies can occur in soils either because they contain extremely low concentrations of these elements or because the elements are present in very unavailable (insoluble) forms. Conversely, many trace elements, including ail of the micronutrients, can reach concentrations in soils that are toxic to plants and microoiganisms. Some of the most toxic are mercury (Hg), lead (Pb), cadmium (Cd), copper (Cu), nickel (Ni), and cobalt (Co). The first three are particularly toxic to higher animals. The last three are more toxic to plants than animals and are termed phytotoxic. From the standpoint of potential hazard to human health, an extended Ust of priority metals has been established. This list presently consists of ... 

A. Yenigiin, B. Taneli, andF. Oksel, 1995. Trace toxic elements in nutrition and health. In Proceeding International Conference on Health and Diseases Effects of Essential Toxic Trace Elements, 4th edn. Pp. 339-340. 

---