Slags, nickel smelting

Endpoint summary

Description of key information

complex metal containing substance
classification derived based on CLP rules for mixtures
solubility of metal constituents is poor
in vitro bio-accessability tests in solution that resembles gastric fluid furter confirm the classification

Additional information

The nickel slag is a complex metal containing substance. It mainly contains iron silicate and silicates of aluminum and calcium. Traces of metals are present in metal forms, mineral form or included in silicate phases

Substance is used in massive, granular or powder form with varying particle size distribution (IUCLID section 4.5). Routes for exposure to consider are therefore oral and inhalation.

Nickel slag is an inorganic solid poorly soluble in water. It is not likely to penetrate through skin in any significant quantity and so would therefore not cause any toxic effects following dermal exposure. Furthermore, negligible metal release in in-vitro bio-accessibility test in artificial sweat fluid was observed (below 1.3% after 1 week)

Classification derived based on rules for mixtures:

Specific organ toxicity, repeated exposure, oral route: Not classified

Based on this result, the related criteria provided the estimated dose/concentration value at or below which no significant toxic effects would be observed in a 90-day repeated-dose study by oral route: Oral(rat), dose concentration >100 mg/kg body weight /day

Specific organ toxicity, repeated exposure, inhalation route: Not classified

Based on this result, the related criteria provided the estimated dose/concentration value at or below which no significant toxic effects would be observed in a 90-day repeated-dose studies: Inhalation rat dust/mist/fume dose/concentration >2 mg/litre/6h/day

Results from calculated classification are further supported (WoE) by consideration of physical chemical properties of the UVCB substance.

Chemistry and mineralogy of the slag (see IUCLID section 4.23 chemical and mineralogical characterization) were taken into account.

Water solubility (IUCLID section 4.8) and Sequential dissolutions (IUCLID 4.23 Chemical assays) furthermore confirmed species present and their solubility behavior

Classification outcome confirmed based on consideration of metal solubilises during in-vitro bio-accessibility tests in solvent that resembles gastric fluid performed according to ASTM D5517.07 (pH 1.5) 

Justification for classification or non-classification

Nickel slag does contain minor constituents classified as STOT RE Cat 1 (ex. Ni compounds) at max actual levels 0.44% thus lower than the generic concentration limit of 1 % triggering classification of the UVCB substance (CLP Annex I, table 3.9.4)

Nickel slag furthermore contains minor constituents classified as STOT RE Cat 2 (ex. Pb compounds) at max actual level 0.02% thus much below the established specific concentration limit of 0.5% which trigger classification of the UVCB substance.

To further confirm the classification in vitro measurements of bio-accessibility in solvent that resembles gastric fluid were performed according to ASTM D5517.07. (pH 1.5) The fraction of metals that solubilize under these conditions can be considered as worst case determinant of bio-accessibility of metals contained in the slag. Results demonstrate reduced relative bio- accessibility of metals (Cu 0.04, Ni 0.05, Co 0.06). Dissolved concentrations of Pb and As were below detection limit.

It can be demonstrated by the measurements that the maximum level of bio-accessible Ni in nickel slag is 0.02% (based on highest % Ni content).

The classification derived is applicable to all nickel slags.See end-point record and discussion above for detailed justifications. 

The assessed samples and derived classifications are representative for a typical nickel slags and defined within the concentration ranges outlined under IUCLID section 1.2.

Self-classification of the UVCB substance (IUCLID Section 2.1 & 2.2) was performed based on the following outline:

 

1. Characterization

The substance is accurately described with elemental composition (typical concentrations and concentration ranges–IUCLID Section 1.2), and specific speciation data (mineralogical composition) obtained from the respective representative samples (IUCLID Section 4, in particular 4.23). This detailed information on the substance identity is used as a basis for the classification.

2. Classification by the rules for mixtures

The UVCB is considered as complex metal containing substance with number of discrete constituents (metals, metal compounds, non-metal inorganic compounds).

The classification is based on concentration thresholds referring to the classified constituents present in the UVCB substance. Specific concentration limits are taken into account.

This concept and classification rules are incorporated in easy to use IT tool which is used to classify the UVCB substance.

3. Bridging or Read-Across

Toxicological data are not available for the specific UVCB being evaluated. Considering variability in composition, read-across and bridging is applied by using representative mineralogical/speciation composition combined withthe metal concentration ranges (see composition in section 1.2)as a basis for the classification of the UVCB substance (chemical and mineralogical surrogates with similar origin/production process and physical/chemical properties (SeeIUCLID 1.4 for information on Sampling procedure).

4. Bioavailability consideration

Data from bio-accessibility test in solution that resembles gastric fluid are available and further confirm the classification.

See Arche Complex Metal Mixture classification calculator (copper version June 2010); MeCLAS webpage: www. meclas. eu