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

Long-term toxicity to aquatic invertebrates

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 invertebrates

Fresh water invertebrates

Effect concentration:

1.7 µg/L

Marine water invertebrates

Marine water invertebrates

Effect concentration:

95.9 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. Therefore, the transformation/dissolution study (OECD guidance 29) was conducted for the substance and the results of this study were used for the chemical safety assessment.

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 the mineralogical composition, zinc appears in sulphide form in the target substance. However, the sulphur is also soluble and can appear either sulphide or sulphate form in water. Since the zinc sulphate is considered to be more bioavailable than zinc sulphide the read-across data and the self-classification of the target substance focuses on the properties of zinc sulphate and other bioavailable forms of zinc (see section 2.2).

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. The weight of evidence approach was used to make conclusions on the key value for CSA.

Toxicity of lead and its compounds

Freshwater toxicity:

The high quality chronic database contains freshwater toxicity data for 2 rotifer species (Philodina rapida; Brachionus calyciflorus), 1 insect (Chironomus tentans), 2 mollusc species (Lymnaea palustris; Lymnaea stagnalis) and 5 crustacean species (Hyalella azteca, Daphnia magna, Ceriodaphnia dubia, Diaphanosoma birgei, Alona rectangula). Chronic freshwater no-effect levels for dissolved lead for invertebrates were situated between 1.7 µg Pb/L (Ceriodaphnia dubia; endpoint reproduction) and 495.7 µg Pb/L (Ceriodaphnia dubia; endpoint: reproduction).

The lowest freshwater toxicity values (7-d EC10 Ceriodaphnia dubia (reproduction)) value: 1.7 µg Pb/L (IC 0.8-3.7 µg/L, EPA 2002)

Marine toxicity:

Chronic marine NOEC and EC10 values were available from 1 species (Neanthes arenaceodentata), values were between 95.9 µg/l to 757.22 µg/l.

The lowest marine toxicity (126-d EC10, (Juvenile emergence), Neanthes arenaceodentata (juvenile emergence)) value: 95.9 µg (95 % IC 40.8-225.3 µg, ASTM Method E1562)

Toxicity of zinc and its compounds

Extensive high quality chronic data were available on 13 different freshwater invertebrate species and 26 marine invertebrate species. These data were all screened for relevancy to the environment under study.

Freshwater toxicity

The freshwater species are part of several different taxonomic groups: poriferans (4 species), molluscs (2 species), crustaceans (4 species), rotifers (2 species) and insects (1 species). The sensitivity of these species is equally distributed over the species sensitivity distribution. Data is available from 13 species. Species NOECs range between 0.037 and 0.400 mg Zn/l (dissolved concentrations).

The lowest freshwater toxicity (NOEC 3-wk, Daphnia magna (growth)) value: 37 µg/L (No guideline)

Marine toxicity

Data is available from 26 species. Species NOECs range between 0.0056 and 0.9 mg Zn/l (dissolved concentrations). The marine species are part of several different taxonomic groups: annelids (4 species), cniderians (1 species), crustaceans (6 species), echinoderms (5 species), molluscs (9 species) and nematods (1 species). The invertebrate species NOECs are combined with the other freshwater and marine chronic data and used in the statistical extrapolation to derive PNEC values.

The lowest marine toxicity (NOEC 24-d, Holmesimysis costata (mortality)) value: 5.6 µg/L (EPA/600/R-95-136)

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, zinc has the lowest key value for freshwater invertebrates, but the lowest key value for marine invertebrates was found from lead. Therefore, the toxicity value from zinc was used for freshwater invertebrates key value and for marine invertebrates key value from lead was used. 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 CSR sections 9&10). All relevant aquatic invertebrate chronic values for lead and zinc were used as a part of the PNEC derivation (statistical extrapolation method).