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1.1 Scope and purpose of the document: The purpose of this document is to assess, evaluate, and give guidance on the role of elemental speciation and speciation analysis in hazard and risk assessment, rather than to present a review of each element and its speciation. The effects on the environment are not considered in this document, as this has been the topic of a recent conference and associated documentation (SGOMSEC, 2003). However, exposure of the human population through environmental routes is considered. This document is directed at risk assessors and regulators, to emphasize the importance of consideration of speciation in their deliberations. Until now, this issue has not been a part of most hazard and risk assessments. Further, one of the aims of the document is to encourage the analysis of speciation of elements to increase knowledge on the effect of speciation on mode of action and understanding of health effects. The emphasis is not on nutritional require ments, but on the toxicity of elements to humans. Consideration is made not only of consumer/general exposure but also of occupational exposure. 1.2 Definitions: A chemical "species" is the "specific form of an element defined as to isotopic composition, electronic or oxidation state, and/or complex or molecular structure". "Speciation" can be defined as the distribution of an element among defined chemical species in a system, and "speciation analysis" as the analytical activities of identifying and/or measuring the quantities of one or more individual chemical species in a sample. 1.3 Structural aspects of speciation: The definitions of species and speciation of elements are based on several different levels of atomic and molecular structure where species differences are manifest. Here, we consider differences at the levels of 1) isotopic composition, 2) electronic or oxidation state, 3) inorganic and organic compounds and complexes, 4) organometallic species, and 5) macromolecular compounds and c |
