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

Sediment toxicity

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

EC10, LC10 or NOEC for freshwater sediment:

573 mg/kg sediment dw

EC10, LC10 or NOEC for marine water sediment:

680 mg/kg sediment dw

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 T/D study results, the most soluble and critical components of this substance are lead and zinc. Furthermore, both lead and zinc also have adsorption potential to sediments and therefore they can be regarded as important for this endoint. The partition coefficients for zinc and lead are presented in section 4.

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

Lead freshwater sediment toxicity

Chronic freshwater toxicity data is available from 7 different sediment dwelling species (Tubifex tubifex, Ephoron virgo, Hyalella azteca, Gammarus pulex, Lumbriculus variegatus, Hexagenia limbata, Chironomus tentans). The NOEC levels were between 573 mg Pb/kg (Tubifex tubifex; endpoint: reproduction) and 3390 mg Pb/kg (Chironomus tentans; endpoint: survival).

The lowest chronic toxicity (28 -d EC10, Tubifex tubifex (reproduction)) value: 573 mg/kg (95% CL: 392-629 µg/kg, ASTM E1383-94)

Lead marine sediment toxicity

The chronic toxicity database for marine sediment dwelling organisms contains toxicity data for 2 marine species (Neanthes arenaceodentataand and Leptocheirus plumulosus). Selected no-effect levels for lead were situated between 680 mg Pb/kg (Neanthes arenaceodentata; endpoint: growth) and 1291 mg Pb/kg (Leptocheirus plumulosus; endpoint: growth).

The lowest chronic toxicity (28-d EC10, Neanthes arenaceodentata (growth rate)) value: 680 mg/kg (conducted following the WES chronic sublethal test method)

Toxicity of zinc and its compounds

Zinc freshwater sediment toxicity

Freshwater chronic toxicity data is available for 7 species. Species mean NOECs used for PNEC derivation range from 201 to 1135 mg/kg dw. In addition, one field study is available for freshwater sediments. Lieber et al. 1996 have reported an overall NOECecosystem of 725 mg/kg d.w. added zinc.

The lowest chronic toxicity (NOEC 35-d Gammarus pulex (growth)) value: 201 mg/kg (Culturing conditions similar to OECD (2005))

Zinc marine sediment toxicity

Marine chronic toxicity data is available for 2 marine species: the amphipod Melita plumulosa with a NOEC reproduction of 730 mg/kg dw. and the mangrove Avicennia marina with a NOEC emergence of 250 mg/kg dw. No field studies were found for marine sediments.

The lowest chronic toxicity (30-wk NOEC, Avicennia marina (growth and survival)) value: 250 mg/kg (OECD 208)

Conclusions for CSA:

Toxicity of the test substance is evaluated by using WoE read-across data from the two critical components of the the test substance (zinc and lead). From the sediment toxicity data, zinc has the lowest toxicity key values to sediment organisms. 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.