Human examples, toxicological hazard

There are many circumstances in which the only information we can develop on toxic hazards and dose-response relationships derives from experiments on laboratory animals. The example of the food additive, presented in the opening pages, is just one of many circumstances in which condition A involves animal toxicology data, and condition B involves a human population, almost always exposed at small fractions of the dose used in animals, and sometimes exposed for much larger fractions of their lifetime than the animals, and even by different routes. Extrapolations under these circumstances should cause individuals trained in the rigors of the scientific method to seek some form of psychological counsel, or, better yet, to return to the laboratory. 

Chemists must become familiar with several fields. For example, the ultimate objective of those working on assessing toxic hazards associated with chemicals, which must be to provide a sound body of knowledge underpinned by validated theory, is still some way off (Richardson, 1986). Assessing the probability that a chemical will be toxic to humans is a complex task. In order to make the correct diagnosis in a particular instance, one would need to be an expert in methods of chemical analysis for tiny concentrations, the physical chemistry of the relevant environment, and the pharmacology and toxicology of the substance. 

Other important toxicological con tarn in ants that can be found in waste-waters are metals. Toxic heavy metal ions are introduced to aquatic streams by means of various industrial activities viz. nfrning, refining ores, fertilizer industries, tanneries, batteries, paper industries, pesticides, etc., and possess a serious threat to the environment. The major toxic metal ions hazardous to humans as well as other forms of hfe are Cr, Fe, Se, V, Cu, Co, Ni, Cd, Hg, As, Pb, Zn, etc. These heavy metals are of specific concern due to their toxicity, bioaccumulation tendency, and persistency in nature [190]. The SLM technique has been widely apphed for the transport and recovery of almost ah important metals from various matrices an exceUent review of ah aspect of metal permeation through SLM (covering both theoretical and practical considerations) is available [191]. Here, only some selected recent examples of the use of SLM for metal separation whl be presented. 

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