Concentrates of lead and zinc compounds with sulfur resulting from hydrometallurgy (hot acid leaching, super-hot acid leaching and flotation)

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The health hazard assessment was conducted based on the most critical constituents of the substance. This substance is an UVCB substance and can be described as a moist solid powder which is insoluble to water. Therefore, the transformation/dissolution study (OECD guidance 29) was conducted for the substance to focus on the most critical and bioavailable constituents of the target substance. The read—across data was selected based on the T/D study results and used for the CSA of the target substance in order to avoid unnecessary animal testing.

The product consists primarily of sulphur (ca. 35 %), lead (ca. 25 %) and zinc (ca. 17 %) together with minor trace elements such as silver, silicon, aluminium, calcium and iron.The transformation and dissolution study (OECD guidance 29) results indicated that the release at pH 6 was higher for all studied elements compared to release at pH 8. Based on the screening test results (loading rate 100 mg/L), the most critical components for the assessment were lead and zinc, with releases of 8282 µg/L and 75.4 µg/L, respectively. The other minor leachable metals were silver (34.7 µg/L), cadmium (0.48 µg/L) and copper (17.2 µg/L).

Results from the 7 day T/D test (loading rate 100 mg/L, pH 6) showed similar trend in release rates: 12333 µg/L (Pb), 91.4 µg/L (Zn), 15.6 µg/L (Cu), 31.4 µg/L (Ag) and 0.056 µg/L (Cd). In the 28 day test with lower loading rate (1 mg/L, pH 6), only concentrations of Pb (362.4 µg/L) and Zn (3.2 µg/L) were over the detection limits or blank sample values.

According to T/D study results, the most soluble and critical components of this substance are lead and zinc. The substance contains also known sensitizers, nickel (0.005 % w/w) and cobalt (0.002 % (w/w)). Since there is only trace amounts of these elements in the substance and the soluble amounts of nickel and cobalt were under detection limit in the leaching study, it is expected that no sensitisation hazard is derived from nickel and cobalt. Also result of the self classification according to the CLP mixture rules indicate that the concentrations of these constituents do not trigger classification of the target substance (C&L procedure is presented in IUCLID section 13). The studies for this endpoint have been selected as a read-across data for soluble Pb or Zn salts. The read-across justification is presented in CSR annex I. The weight of evidence approach was used to make conclusions on the key value for CSA.

Pb compounds

Animal and human data specifically evaluating skin or lung sensitisation were not found. However, in view of the lack of toxicity, irritation or reports of sensitisation from occupational exposure settings, lead compounds do not appear to pose risk of sensitisation.

Zn compounds

Zinc sulphate (ZnSO4•7 H2O) was tested in a mouse local lymph node assay (Ikarashiet al., 1992. After gentle dermal abrasion, 25 ml of a 5 % zinc sulphate solution in 20% ethanol was applied for three consecutive days at the dorsal side of both ears of three Balb/c mice. On the fourth day the animals were sacrificed and the ear-draining lymph nodes were collected. Lymph node lymphocyte proliferation was determined by tritiated thymidine incorporation. The results were compared to those of vehicle-treated controls. Zinc sulphate did not induce proliferative activity, whereas for potassium bichromate, nickel sulphate and cobalt chloride (known dermal sensitizers) positive results were obtained.

The skin sensitising potential of zinc sulphate (ZnSO4•7 H2O) was also investigated in guinea pigs. A well-performed maximisation test, conducted according to Directive 96/54/EC B.6 and OECD guideline 406, was carried out in female Dunkin Hartley guinea pigs. Based on the results of a preliminary study, in the main study 10 experimental animals were intradermally injected with a 0.1% concentration and epidermally exposed to a 50% concentration. Five control animals were similarly treated, but with vehicle (water) alone. Approximately 24 hours before the epidermal induction exposure all animals were treated with 10% SDS. Two weeks after the epidermal application all animals were challenged with a 50% test substance concentration and the vehicle. A second challenge followed one week after the first. In response to the 50% test substance concentration, in some experimental animals and controls skin reactions of grade 1 were observed 48 hours after the first (5/10 and 2/5, respectively) and the second challenge (4/10 and 2/5, respectively). As the skin reactions were comparable among the experimental and control animals, and as there was poor consistency of the skin reactions among individual experimental animals after the first and second challenge, the observed skin reactions can be considered to be non-specific signs of irritation. Hence, it can be concluded that zinc sulphate did not induce hypersensitivity in experimental animals (Van Huygevoort, 1999i).

Conclusions

The assessment of the sensitisation potency of the substance was based on the overall weight of evidence from the composition of the substance and the bioavailability and the toxicity of the most critical components (zinc and lead compounds). According to the sensitisation test results from these components the target substance is not expected to cause the risk of sensitisation. Thus, no classification for sensitisation is warranted.

Migrated from Short description of key information:
According to transformation/dissolution study (OECD guidance 29) conducted for the substance, the most critical constituents leachable to water from this UVCB substance are lead and zinc compounds. Therefore, the chemical safety assessment focuses on the properties of constituents and the key values for CSA are selected based on the read-across data on the most bioavailable compounds of Pb and Zn.

Taking into account the complete absence of skin sensitization potential of zinc compounds and the lack of sensitisation from occupational exposure settings of lead compounds, skin sensitisation is not expected to be of concern for the substance considered in this chemical safety assessment.

Justification for selection of skin sensitisation endpoint:
No study conducted for the target UVCB substance. Also no endpoint selection was made since the endpoint conclusion is based on the weight of evidence from the read-across substances (ie. bioavailable lead and zinc compounds).

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Migrated from Short description of key information:
No respiratory sensitisation studies are conducted for the substance or the most critical components of the substance. Taking into account the complete absence of skin sensitization potential of zinc compounds and the lack of sensitisation from occupational exposure settings of lead compounds, respiratory sensitisation is not expected to be of concern for the substance considered in this chemical safety report.

Justification for selection of respiratory sensitisation endpoint:
No respiratory sensitisation studies are conducted for the substance or the most critical components of the substance. Taking into account the complete absence of skin sensitization potential of zinc compounds and the lack of sensitisation from occupational exposure settings of lead compounds, respiratory sensitisation is not expected to be of concern for the substance considered in this chemical safety report.

Justification for classification or non-classification

Based on the self-classification of the target substance which was conducted taken into account the concentrations of the constituents classified as sensitizers, the CLP mixture rules do not trigger this substance to be classified. In addition, the read-across data for the main and the most critical constituents (lead and zinc compounds) of the target substance does not show any sensitising properties to classify.