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Ecotoxicological Summary

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The approach for deriving PNEC values was used in the 2008/2009 European Union Existing Substances Risk Assessment of Nickel (EU RAR) (EEC 793/93). The EU RAR was jointly prepared by the Danish Environmental Protection Agency (DEPA), which served as the Rapporteur of the Existing Substances Risk Assessment of Nickel, and the Nickel Producers Environmental Research Association (NiPERA), which represented the Nickel Industry in this process. The complete Environment section of the EU RAR can be found in the pdf linked to the following URL:


All of the approaches described were discussed by the Technical Committee for New and Existing Substances (TC NES), and received final approval at the TC NES I meeting in April, 2008.


Common effects assessment basis:


The ecotoxicity databases on the effects of soluble nickel compounds to aquatic, soil- and sediment-dwelling organisms are extensive. It should be noted that the effects assessments of Nickel subsulfide is based on the assumption that adverse effects to aquatic, soil- and sediment-dwelling organisms are a consequence of exposure to the bioavailable Ni-ion, as opposed to the parent substances. The result of this assumption is that the ecotoxicology will be similar for all soluble Ni substances used in the ecotoxicity experiments. Therefore, data from soluble nickel substances are used in the derivation of chronic ecotoxicological NOEC and L(E)C10 values. If both NOEC and L(E)C10 data are available for a given species, the L(E)C10 value was used in the effects assessment.

Conclusion on classification

Ni subsulfide is classified as Aquatic Acute I/Chronic I in the 1st ATP to the CLP regulation. Classification was confirmed by the results of the Tranformation/Dissolution Screening Test.

The 2ndATP to the CLP regulation requires the application of both an acute and a chronic multiplying (M)- factor for the derivation of classifications for mixtures containing nickel subsulfide. The appropriateness of the identified acute and chronic M-factors (acute M-factor =1, chronic M- factor =1) is under review and a Weight of Evidence Approach utilizing newly generated toxicity data will be applied to determine the need for a revision to the nickel subsulfide acute or chronic M-Factor reported herein.

The acute and chronic M-Factor for nickel is determined by the acute and chronic Ecotoxicity Reference Value (ERV) respectively, and adjusted by the molecular weight of the compound. The acute and chronic ERVs for nickel and nickel compounds were derived in 2006 in conjunction with the Danish Environmental Protection Agency and the EU Classification and Labeling Committee. The acute and chronic ERVs were derived using the lowest species mean values available in 2006. As nickel toxicity is dependent on pH, acute ERVs were developed at pH 6 using the freshwater algae Pseudokirchneriella subcapitata (ERV = 120 µg Ni/L) and at pH 8 using the cladoceran Ceriodaphnia dubia (ERV = 68 µg Ni/L). The single chronic ERV was developed usingC. dubia (ERV = 2.4 µg Ni/L).

Since the derivation of these values in 2006, the availability of new ecotoxicological data and changes to the Guidance to Regulation (EC) No 1272/2008 on classification, labeling and packaging (CLP) of substances and mixtures (2012) suggest that the appropriateness of the 2006 nickel ERV values should be reevaluated. Importantly, the new CLP guidance now allows theuse of probabilistic methods (i.e. Species Sensitivity Distribution (SSD)), instead of the lowest species value: “In cases of very large data sets meeting the criteria for applying theSpecies Sensitivity Distribution (SSD) approach, statistical techniques can be considered to estimate the aquatic toxicity reference value for classification (equivalent to using the lowest EC50 or NOEC), in a weight of evidence approach” (p. 416).The nickel freshwater ecotoxicity database is one of the most robust datasets available for any metal and the SSD approach for nickel has been successfully implemented and is documented in the EU Existing Substances Risk Assessment of Nickel and Nickel Compounds (ECB 2008) and in the current nickel subsulfide CSR. The new CLPguidance also recognizes the use of bioavailability normalization for metals and metal compounds: “Bioavailability and speciation models (e.g.Biotic Ligand Modelsand WHAM (Tipping, 1994) may allow to normalize ecotoxicity data obtained at a given pH to other pH values, relevant to the T/D data” (p. 501). Nickel Biotic Ligand Models (BLMs) have been developed and validated for algae, invertebrates, and fish species. The nickel BLMs served as the basis for bioavailability normalization in the EU Existing Substances Risk Assessment of Nickel and Nickel Compounds (ECB 2008), and also serve as the means to incorporate bioavailability into the Nickel Environmental Quality Standard under the Water Framework Directive[1]. The nickel BLMs are therefore suitable for normalizing nickel ecotoxicity data to the pH values that are used in the Transformation/Dissolution Protocols, which produce exposure data used in the determination of appropriate classification of nickel and nickel compounds.

Several new ecotoxicity datasets have become available since the assessment in 2006 that suggest that a review of the ERVs is needed. Acute toxicity testing on C. dubia by AECOM Technical Services Inc. in 2011 resulted in 48hr LC50 values ranging from 296 µg Ni/L to 593 µg Ni/L, which are significantly greater than the ERV derived using the LC50 Geometric Mean of 68 µg Ni/L (section New data published by Cloran et. al.; 2010, Ferriera et. al., 2010; Liber et. al., 2011; Schlekat et. al., 2010; and others (section and should be further evaluated for use in the SSD approach for deriving appropriate science-based ERVs. This evaluation is currently underway and will conclude in 2013. The acute and chronic environmental classifications and M-factors may be revised accordingly.


The 2ndATP to the CLP introduced the chronic (long-term) environmental toxicity endpoint as defined by the 3rdversion of the UN-GHS into the EU hazard classification and labeling scheme. The GHS and EU scheme include the concept of degradation whereby rapid degradation from the water column (greater than 70 % removal in 28 days) results in different classification cut-off values and categories.  For metals and inorganic metal compounds, the rapid and irreversible removal from the water column is equated to the rapid degradation concept for organics.  The current draft guidance on metals includes  a proposal to apply the “rapid degradation principle for organics” measured as a 70 % removal rate in 28 days in a comparable way for metals from laboratory and field experiments or by using a recently developed model.  A Unit World Model (UWM) has recently been developed specifically for metals, building on previous screening-level calculations that have been developed for organic contaminants, and is capable of assessing the fate and effects of chemicals by the simultaneous consideration of chemical partitioning, transport, reactivity, and bioavailability.  With regard to hazard assessment, the UWM is capable of assessing the removal of soluble metals from the water column resulting from sorption to particulate material, settling to the sediment compartment, and subsequent changes in speciation via precipitation by sulfides naturally present in the sediment compartment. 


The UWM was used to assess the rapid removal of a group metals (e.g., Ni, Cu, Pb, Zn, As, Al, Co) in a generalized lake environment resulting from metal removal from the water column and sequestration in sediment.  To estimate sorption by particulate matter in the water column, the UWM can use empirical, measured distribution coefficients (Kd), or the speciation module within the UWM (the Windermere Humic Aqueous Model, or WHAM) can calculate Kds. When an empirical Kd of log 4.42 was used, greater than 70% nickel removal was achieved in every loading and pH scenario. WHAM-based Kds tended to be substantially lower than empirical Kds, indicating that refinement of the WHAM approach was needed. To this end, the UWM was refined to accommodate an updated version of WHAM (WHAM 7). Additionally, the inorganic thermodynamic database used by WHAM to perform speciation calculations was updated because the previous version was found to be out of date and inaccurate. Analyses using WHAM7 and the revised inorganic thermodynamic database showed that greater than 70% nickel removal was achieved under the three pH scenarios with metal loadings at the acute and chronic ERVs at 28 days.  At the upper chronic cutoff value of 1 mg/L, rapid removal was achieved for pH 6 and 8 without oxide binding and for all three pH values with oxide binding.  Rapid removal was demonstrated at all pH values when loading was based on acute Ecotoxicity Reference Values (120 µg Ni/L at pH 6 and 68 µg Ni/L at pH 8) and chronic Ecotoxicity Reference Values (2.4 µg Ni/L) using calculated Kd values. Based on these results, nickel subsulfide fulfills the criteria for rapid degradation for the environmental classification scheme in the 2ndATP to the CLP.