A new approach to the hazard classification of alloys based on transformation/dissolution

Abstract

Most of the metals produced for commercial application enter into service as alloys which, together with metals and all other chemicals in commerce, are subject to a hazard identification and classification initiative now being implemented in a number of jurisdictions worldwide, including the European Union Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) initiative, effective 1 June 2007. This initiative has considerable implications for environmental protection and market access. While a method for the hazard identification and classification of metals is available in the recently developed United Nations (UN) guidance document on the Globally Harmonized System of Hazard Classification and Labelling (GHS), an approach for alloys has yet to be formulated. Within the GHS, a transformation/dissolution protocol (T/DP) for metals and sparingly soluble metal compounds is provided as a standard laboratory method for measuring the rate and extent of the release of metals into aqueous media from metal‐bearing substances. By comparison with ecotoxicity reference data, T/D data can be used to derive UN GHS classification proposals. In this study we applied the T/DP for the 1st time to several economically important metals and alloys: iron powder, nickel powder, copper powder, and the alloys Fe‐2Cu‐0.6C (copper =2%, carbon = 0.6%), Fe‐2Ni‐0.6C, Stainless Steel 304, Monel, brass, Inconel, and nickel‐silver. The iron and copper powders and the iron and nickel powders had been sintered to produce the Fe‐2Me‐0.6C (Me = copper or nickel) alloys which made them essentially resistant to reaction with the aqueous media, so they would not classify under the GHS, although their component copper and nickel metal powders would. Forming a protective passivating film, chromium in the Stainless Steel 304 and Inconel alloys protected them from reaction with the aqueous media, so that their metal releases were minimal and would not result in GHS classification. For the other alloys, we developed a new critical surface area‐toxic units (CSA‐TU) approach to derive their GHS classification proposals. The CSA‐TU approach can be readily applied to other multicomponent alloy systems, without the need to arbitrarily select a particular component among several as the determinant of toxicity. This paper shows how regulatory obligations, such as those mandated by REACH, can be met with a laboratory‐based CSA‐TU method for deriving hazard classification proposals for alloys, linking to attendant environmental protection management decisions. Drawing on T/D data derived from laboratory testing of the alloy itself, the CSA‐TU approach can be applied to establish scientifically defensible decisions on hazard classification proposals for an alloy of interest. The resulting decisions can then be incorporated into environmental management measures in such jurisdictions as the European Union. Based on an approach developed specifically for alloys, the hazard classification decisions can be regarded as relevant, credible,...

Bioaccessibility, bioavailability and toxicity of commercially relevant iron- and chromium-based particles: in vitro studies with an inhalation perspective

“…The reason is most probably combined effects of particle agglomeration (more commonly occurring for small-sized particles), confirmed by the light diffraction measurements for small particles, and/or a thermodynamic equilibrium shift between released metal ionic species in solution and the metal surface in the closed experimental system (smaller particles are releasing more dissolved metal into solution, which then decreases further dissolution due to thermodynamic considerations). Similar effects have been observed in other biological systems [10,13,18,20,24]. Particle agglomeration has previously been shown to decrease the initial release of copper from non-sonicated copper metal nanoparticles compared with sonicated particles [23].…”

Transformation/dissolution characterization of tungsten and tungsten compounds for aquatic hazard classification

“…T/D reaction kinetic data were generated for 3 tungsten carbides of different measured specific surface areas in order to calculate the critical surface area. This approach is consistent with similar correlations of 7‐d metal concentrations to surface area loadings for Ni metal and several alloys that were reported previously (Skeaff et al ).…”

“…Because details of the T/DP experimental procedure, including cleaning of glassware, methods of agitation and temperature control, aqueous medium compositions, pH control, pH and dissolved O measurement, sampling procedure, and calculation of net concentrations have been presented previously (Skeaff et al , , ; Huntsman‐Mapila et al ), only aspects of the present procedure that differed from those already reported are presented. The UN T/DP (UN ) was followed, which calls for agitating weighed quantities of the substance of interest in 1 L of aqueous medium based on the OECD 203 medium for ecotoxicity testing (OECD ) in the temperature range 20 to 23 °C, sampling at specified intervals, and determining the concentrations of the dissolved analytes of interest.…”

Transformation/dissolution examination of antimony and antimony compounds with speciation of the transformation/dissolution solutions

“…We have previously presented in some detail the T/DP experimental procedure, including methods of agitation and temperature control, aqueous media compositions, pH control, pH and dissolved O 2 measurement, and sampling procedure (Skeaff et al 2008, 2011). Essentially, the experimental procedure involves agitating weighed quantities of the test substance in 1 L of aqueous media based on the OECD 203 medium for ecotoxicity testing (OECD 1992) in the temperature range 20°C to 23°C, followed by sampling and analyzing the solutions for the metals of interest.…”

“…We have outlined the GHS aquatic hazard classification framework, scheme, and applications for metals, metal compounds, and alloys in previous publications (Skeaff et al 2008, 2011). Essentially, comparisons of selected acute ecotoxicity reference values (ERVs) with dissolved metal concentrations released at specified intervals under standard transformation/dissolution (T/D) conditions (Skeaff et al 2006; UN 2011) into standard aqueous media from mass loadings of 1, 10, and 100 mg/L of the test substance establish the corresponding Acute 1, 2, and 3 hazard classification levels of the scheme.…”