An effective concentration approach to classify alloys

The poster explaining the unique properties of alloys as ‘special mixtures’ and the metals industry’s proposed application of bioelution based approaches for the classification of alloys was presented by Dr. Adriana Oller, NiPERA in collaboration with the European Copper Institute and Eurometaux at the Institut National de l’Environnement Industriel et des Risques conference Chemical risk: innovative methods and techniques held 8-10 April, 2015 in Nancy, France.

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  • Most metals on the market are used as alloys; alloys are considered ‘special preparations’ of metals since their properties differ from those of their metal components.
  • Appropriate chemical management practices, including classification, are essential to ensure the safe use of alloys (e.g., UN GHS and EU CLP).
  • The default approach for the classification of alloys (as mixtures) is to directly compare the alloy content of classified metals to the classification criteria (i.e., summation rules or additivity formula for acute toxicity classification and cut-off concentration/limit approaches for the other toxicological endpoints).
  • In general, the toxicity of metals and alloys is considered to be related to the bioavailability of the metal ion. Due to the alloys’ properties, the extent of the metal ion release from alloys (and thus its bioavailability) can be significantly different from the releases from their pure metal constituents.
  • Bioelution testing measuring metal ion releases in synthetic body fluids (bioaccessibility) relevant to each route of exposure can be used in the calculation of the effective concentration of classified metals in alloys.
  • An overall framework for the human health classification of alloys is proposed, starting from the collection and evaluation of available data and following three tiers of assessment that range from using alloy-specific toxicity data for classification, to bridging information across alloy samples, to using effective concentration of classified metals in an analogous way as simple mixture concentrations.
  • The bioelution-derived effective concentration of metals in alloys has been shown to be a better predictor of in vivo toxicity than concentration. The use of effective concentration of metals in alloys allows refinement of the classification for these special and important substances.

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