slag, copper 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 copper slag is a complex metal containing substance. It mainly contains iron silicate and silicates of aluminum and calcium.

Traces of metals exist in metal, 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.

Copper 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 (1.9 -2.5% or 0.021 to 0.036 µg Ni/cm2/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 theestimated dose/concentration value at or below which nosignificant toxic effects would be observed in a 90-day repeated-dose studyby 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 refined (Higher tier) based on consideration of the fraction of Pb that solubilizes 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

Copper slag does contain minor constituents classified as STOT RE Cat 1 and Cat 2 (Ni and Pb compounds). Maximum actual levels of Ni up to 0.25% are lower than the generic concentration limit of 1% for STOT RE 1. At maximum actual levels up to 0.6%, Pb compounds trigger the classification of the UVCB substance as STOT RE 2 above the specific concentration limit of 0.5%.

Oral route

To further refine the classification in vitro measurements of bio-accessibility in solvent that resembles gastric fluid performed according to ASTM D5517.07. 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 in gastric fluids. In a Tier 2 assessment of final copper slag samples, absolute bioaccessible concentration of Pb are in the range 0.008% to 0.06% thus below the concentration limit of 0.5% for specific target organ toxicity (STOT RE 2).

Inhalation route

Inhaled lead particles have systemic mode of action so resorption of dissolved lead particles can take place from deposition locations in the entire respiratory tract and contribute to systemic toxicity.

An acute inhalation toxicity study conducted with lead oxide powder (MMAD= 5.8µm) showed that deep lung penetration would be minimal and upper respiratory tract deposition would predominate (Ref, Lead voluntary risk assessment) / Upper respiratory tract deposition would in turn be followed by clearance to the gastrointestinal tract. Pulmonary deposition modelling further showed that deposition patterns for all thirteen lead compounds will be rather similar. No signs of any respiratory irritation or any other clinical observations

Thus, systemic lead uptake from slag is predicted to be similar to that for lead oxide.

Finally, a conservative assumption is made that all lead containing particles in the slag will deposit in the upper airways, such particles will than enter the gastrointestinal tract, where further uptake of all dissolved particles will take place.

A separate assessment report on the Human health classification of copper final slag is attached in IUCLID section 13.

Therefore consideration of reduced bio-accessibility of Pb will lead to No classification of copper slags for STOT repeated exposure by oral and inhalation route.