Advances in metals classification under the United Nations globally harmonized system of classification and labeling

This article shows how regulatory obligations mandated for metal substances can be met with a laboratory-based transformation/dissolution (T/D) method for deriving relevant hazard classification outcomes, which can then be linked to attendant environmental protection management decisions. We report the results of a ring-test at 3 laboratories conducted to determine the interlaboratory precision of the United Nations T/D Protocol (T/DP) in generating data for classifying 4 metal-bearing substances for acute and chronic toxicity under the United Nations Globally Harmonized System of Classification and Labelling (GHS) criteria with respect to the aquatic environment. The test substances were Ni metal powder, cuprous oxide (Cu(2) O) powder, tricobalt tetroxide (Co(3) O(4) ) powder, and cuttings of a NILO K Ni-Co-Fe alloy. Following GHS Annex 10 guidelines, we tested 3 loadings (1, 10, and 100 mg/L) of each substance at pH 6 and 8 for 7 or 28 d to yield T/D data for acute and chronic classification, respectively. We compared the T/DP results (dissolved metal in aqueous media) against acute and chronic ecotoxicity reference values (ERVs) for each substance to assess GHS classification outcomes. For dissolved metal ions, the respective acute and chronic ERVs established at the time of the T/D testing were: 29 and 8 µg/L for Cu; 185 and 1.5 µg/L for Co; and 13.3 and 1.0 mg/L for Fe. The acute ERVs for Ni were pH-dependent: 120 and 68 µg/L at pH 6 and 8, respectively, whereas the chronic ERV for Ni was 2.4 µg/L. The acute classification outcomes were consistent among 3 laboratories: cuprous oxide, Acute 1; Ni metal powder, Acute 3; Co(3) O(4) and the NILO K alloy, no classification. We obtained similar consistent results in chronic classifications: Cu(2) O, Ni metal powder, and Co(3) O(4) , Chronic 4; and the NILO K alloy, no classification. However, we observed equivocal results only in 2 of a possible 48 cases where the coefficient of variation of final T/D concentrations masked clear comparisons with ERVs. Results support the validity and interlaboratory precision of the United Nations T/DP in establishing GHS classification outcomes for metals and metal compounds and support its use in regulatory hazard-based systems. Drawing on T/D data derived from laboratory testing of the metal-bearing substance itself, the T/D approach can be applied to establish scientifically defensible decisions on hazard classification proposals. The resulting decisions can then be incorporated into environmental management measures in such jurisdictions as the European Union.