Bis(glycinato-N,O)zinc

Endpoint summary

Description of key information

- Short-term toxicity to aquatic invertebrates: RL2, no guideline followed, but well documented: The LC50 value chosen in this approach is 0.799 mg Zn²⁺/L according to Attar and Maly (1986). This corresponds to a 48-h LC50 of 2.61 mg bis(glycinato-N,O)zinc/L in Daphnia magna.

- Toxicity to aquatic algae and cyanobacteria: The 48-h LC50 for aquatic algae was determined in various studies. The EC50 value chosen in this approach is 0.133 mg Zn²⁺/L according to De Schamphelaere et al., 2004. This corresponds to a 72-h EC50 of 0.434 mg bis(glycinato-N,O)zinc/L in Pseudokirchneriella subcapitata.

Additional information

There is no information available on aquatic toxicity of bis(glycinato-N,O)zinc. However, based on the information available for the single constituents, namely glycine and Zn²⁺, the read-across is based on the hypothesis that metal ions chelated with amino acids are not more toxic than the metal ions alone.

The anion of the target substance is the essential amino acid glycine and in the source substances it is the chloride and sulfate anion. These anions are not considered as ecotoxicologically relevant at the given concentrations. Instead, Zn²⁺is the ecotoxicologically critical component.

The 48-h EC50 or LC50 for aquatic invertebrates (Daphnia magna) was determined in various studies. The LC50 value chosen in this approach is 0.799 mg Zn²⁺/L according to Attar and Maly (1986), for the following reasons: the reported 48-h EC50 values in the most reliable studies (RL2) range from 0.799 to 6.03 mg Zn²⁺/L. The well documented studies by Attar and Maly (1986) and Heijerick et al. (2002) report 48-h values of 0.799 (LC50) and 0.93 mg Zn²⁺/L (EC50), respectively, which are in a very close range. For precautionary reasons, the more conservative value was chosen.

Apart from effect concentrations, Park et al. (2019) as well as Ergönül et al. (2012) report adverse effects of Zn²⁺on Daphnia magna like internal injuries, lethargy, corrosion in the carapax and partial ruptures. However, the respective effective concentrations were comparably high (48-h EC50 were 1.98 and 6.03 mg Zn²⁺/L).

The 48 -h LC50 value chosen in this approach is 0.799 mg Zn²⁺/L.

This corresponds to a 48-h LC50 of 2.61 mg bis(glycinato-N,O)zinc/L in Daphnia magna.

There is no information available on aquatic toxicity of bis(glycinato-N,O)zinc. However, based on the information available for the single constituents, namely glycine and Zn²⁺, the read-across is based on the hypothesis that metal ions chelated with amino acids are not more toxic than the metal ions alone.

The anion of the target substance is the essential amino acid glycine and in the source substances it is the chloride and sulfate anion. These anions are not considered as ecotoxicologically relevant at the given concentrations. Instead, Zn²⁺is the ecotoxicologically critical component.

The EC50 for aquatic algae were determined in various studies. The reported 72- or 96-h EC50 values in reliable studies range from 0.08 to 2.432 mg Zn²⁺/L. The zinc toxicity in green algae was shown to be strongly dependent on the examined species. The most sensitive species was Pseudokirchneriella subcapitata (72-h EC50: 0.133 mg Zn²⁺/L), while Ankistrodesmus falcatus (96-h EC50: 2.432 mg Zn²⁺/L), Chlorella vulgaris (96-h EC50: 2.4 mg Zn²⁺/L) and Desmodesmus subspicatus (96-h EC50: 2.258 mg Zn²⁺/L) were far less sensitive.

The EC50 value chosen in this approach is 0.133 mg Zn²⁺/L according to De Schamphelaere et al. (2004) for the following reasons: the study reported by De Schamphelaere et al. (2004) was conducted according to OECD guideline 201 (RL1) using the sensitive species Pseudokirchneriella subcapitata, for regular 72 hours. In the other studies using Pseudokirchneriella subcapitata by Al-Hasawi et al.(2020) and Rojíčková-Padrtová and Maršálek (1999), no guideline was followed and the study duration was 96 h.

The 72-h EC50 value chosen in this approach is 0.133 mg Zn²⁺/L.

This corresponds to a 72-h EC50 of 0.434 mg bis(glycinato-N,O)zinc/L in Pseudokirchneriella subcapitata.