The Elements in Toxicology

The toxicological significance of the chemical form does not only derive from the fact that the great majority of the elements in the periodic table are metals and metalloids many metals also make it possible to demonstrate the dose-effect relationship very clearly. Copper, manganese, selenium, cobalt and zinc, for example, are essential trace elements whose absence inevitably results in deficiency symptoms or loss of proper functioning. On the other hand, large doses are cytotoxic or cause cancer. 

Kinetics is the study of the speed of a chemical reaction or process and is a critical element in toxicology. Most processes described in the discipline follow zero- and first-order kinetics. Recall that rate laws are employed to determine concentrations as a function of time. Although there are other variables and factors, the elimination of a xenobiotic substance from the body is fundamentally dependent on the kinetics of the reactions involved. Elimination processes often involve catalysts (enzymes), the role of which is central in determining the overall speed of the elimination, since a catalyst reduces the energy of activation. Eg. 

Total Elements There is a dearth of elemental concentration data for a wide range of nutritionally, toxicologically, clinically, and environmentally pertinent elements. Some of the elements for which total concentration information is still required, usually at the low end of concentration range but occasionally at the high end, are Al, Ba, B, Be, Br, Cs, F, I, Li, Mo, N, Pt, S, Sb, Si, Sn, Th, Ti, TI, U, V, W, rare earth elements, and radionuclides. Thus, it would seem advisable to certify each new RM for as many elements as possible so that certified values would be available for a larger number of elements in addition to the small number of core elements typical of many current RMs. 

Principles and Characteristics The fastest growing area in elemental analysis is in the use of hyphenated techniques for speciation measurement. Elemental spe-ciation analysis, defined as the qualitative identification and quantitative determination of the individual chemical forms that comprise the total concentration of an element in a sample, has become an important field of research in analytical chemistry. Speciation or the process yielding evidence of the molecular form of an analyte, has relevance in the fields of food, the environment, and occupational health analysis, and involves analytical chemists as well as legislators. The environmental and toxicological effects of a metal often depend on its forms. The determination of the total metal content... 

The toxicokinetic and toxicological behavior of lead can be affected by interactions with essential elements and nutrients (for a review see Mushak and Crocetti 1996). In humans, the interactive behavior of lead and various nutritional factors is particularly significant for children, since this age group is not only sensitive to the effects of lead, but also experiences the greatest changes in relative nutrient status. Nutritional deficiencies are especially pronounced in children of lower socioeconomic status however, children of all socioeconomic strata can be affected. 

Animal studies indicate that nutritional deficiencies in a number of essential elements (e.g., calcium, iron, zinc, copper, phosphorus) may impact the toxicokinetic and toxicological behavior of lead (ATSDR 1993 Chaney et al. 1989). In infants and children, lead retention has been shown to be inversely correlated with calcium intake (Johnson and Tenuta 1979 Sorrell et al. 1977 Ziegler et al. 1978). Zinc has been shown to have a protective effect against lead toxicity in a number of animal species (Goyer 1986 Haeger-Aronsen et al. 1976 Brewer et al. 1985 Cerklewski and Forbes 1976). 

Trace level analyses are frequently required for forensic, clinical and toxicological applications and for better understanding of the fate of individual pollutants in the environment, where not only the element is determined but the organic species are also identified and individualy quantified. These analyses can be performed with or without actual separation of the individual species. 

The handling of the biocide supply as the potassium salt rather than in the elemental form circumvented the toxicological and corrosive problems associated with iodine. In addition, the sodium metabisulfite stream is available to reduce the iodine in the product stream prior to demineralization in the mixed bed ion exchanger. 

Metals that are potentially biologically active, either therapeutically or toxicologically, may be divided into the following groups, based upon their electron configuration and position in the periodic table of the elements ... 

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