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

Short-term toxicity to fish

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.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

40.8 µg/L

Additional information

The environmental hazard assessment was conducted based on the most critical constituents of the substance. This substance is an inorganic UVCB substance and can be described as a moist solid powder which is insoluble to water. The critical consituents were selected based on the transformation/dissolution study (OECD guidance 29) conducted for the substance.

According to the chemical composition analysis, the main phases of the substance are lead sulphate and zinc sulphide. 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.

According to T/D study results, the most soluble and critical components of this substance are lead and zinc. Therefore, the studies for this endpoint have been selected as a read-across data for the critical constituents. The read-across justification is presented in CSR annex I. All read-across data for ecotoxicology are based on test data using either soluble Pb or Zn salts or measured (dissolved) Pb or Zn concentrations.

Toxicity of lead and its compounds

Freshwater

For fish, 47 individual reliable acute toxicity data points for two different species were put forward for hazard assessment purposes. The acute toxicity values (96h-LC50) for Pimephales promelas varied between of 40.8 µg dissolved Pb/L (at pH 5.67 and hardness of 15.9 mg/L) and 3597.9 µg dissolved Pb/L (at pH 7.1 and hardness of 26 mg/L). The acute toxicity values (96h-LC50) for Oncorhynchus mykiss varied between of 107.0 µg dissolved Pb/L (at pH 8.8 and hardness of 290 mg/L) and 1170.0 µg dissolved Pb/L (at pH 6.9 and hardness of 32 mg/L).

The lowest acute freshwater toxicity (EC50 96-h, Pimephales promelas (mortality)) value: 40.8 µg/L (95 % CI: 32.1- 48.3, US EPA 2002)

Toxicity of zinc and its compounds

Freshwater

Dataset has good quality and relevant data for 5 species. Tests were done according to standard protocol or equivalent. Data are grouped per species according to pH: low (6 -<7), neutral/high (7 -8.5) and hardness: low/medium (<100 mg CaCO3/l) and medium/high (> 100 mg CaCO3/l). Fish are generally less sensitive than invertebrates and algae.

Key data (lowest LC50 values) for Oncorhynchus mykiss: 0.169 mg Zn/l (single value) at neutral/high pH and low hardness, for Pimephales promelas (single values): 0.780 mg Zn/l at low pH (high hardness) and 0.330 mg Zn/l at neutral/high pH, high hardness, for Pimephales promelas: LC50 0.780 mg Zn/l (at low pH); 0.33mg Zn/l at neutral/high pH.

The lowest freshwater toxicity (LC50 96-h, Oncorhynchus mykiss (mortality)) value: 0.169 mg Zn/l (95% CI 118-243, ASTM E-729-88).

Conclusions for CSA:

Toxicity of the test substance is evaluated by using WoE read-across data from the two critical components of the test substance (zinc and lead). From the toxicity data, lead has the lowest key value for short-term toxicity to fish. Therefore, the toxicity values from lead were used as key value for CSA. However, as lead and zinc are both relevant for environmental ES&RC, key values from both constituents were used for PNEC-derivation and taken into account in the exposure assessment (see section 9&10 of CSR).