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Long-term toxicity to fish

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Description of key information

One reliable long term toxicity study (Klimisch 1, GLP) for a fish species -the zebrafish danio rerio - was conducted. No effect (mortality) was noted at the highest measured test concentration of nominal 100 mg strontium nitrate/L. Re-calculation from strontium nitrate to strontium sulfide leads to an NOEC of >= 56.6 mg SrS/L and a LOEC of > 56.6 mg SrS/L.
Toxicity data for sulfate were not identified; it should be noted that sulfide will rapidly oxidize to the less toxic sulfate under normal environmental conditions that are relevant for the aquatic environment. Sharma and Yuan (2010), for example, demonstrated that sulfide is oxidised to sulfate and other oxidised S-forms in less than one hour.

Key value for chemical safety assessment

Additional information

Reliable chronic toxicity data for fish are available for strontium and sulfide but not for sulfate.

The lowest reliable chronic toxicity for fish with regard to sulfide was reported by Smith et al (1976a) for mortality of the juvenile bluegillLepomis macrochirus, yielding in an unbounded 826d-NOEC of 0.0046 mg H2S/L. Toxic effects of released sulfide from SrS are not relevant for the chronic hazard assessment of SrS as it is oxidized to sulfate, and thus the toxicity of sulfate should be assessed. In freshwater, however, sulfate appears to be of low toxicity to fish with acute LC/EC50 values far above 1000 mg/L. The solubility product constant of strontium sulfate of ~3 × 10–7 indicates that once sulfide released from SrS is oxidized to sulfate, and that celestite (SrSO4) precipitates. Further, sulfate is essential to all living organisms, their intracellular and extracellular concentrations are actively regulated and thus, sulfates are of low toxicity to the environment (OECD SIDS for Na2SO4). Therefore, it may conservatively be assumed that the toxicological moiety of concern for the long-term toxicity of SrS to fish (if any) is strontium and further that the contribution of sulfate to the overall toxicity of SrS may be neglected.

One reliable long-term toxicity study (Klimisch 1, GLP) withDanio reriowas conducted. No effects were abserved at the highest test concentration of nominal 100 mg strontium nitrate/L corresponding to the following unbounded NOEC value: 

-      NOEC ≥ 56.6 mg SrS/L (≥ 41.4 mg Sr/L) based on nominal strontium concentration.

It is concluded that the chronic toxicity of SrS under normal environmental conditions is determined by the release of strontium, and the unbounded NOEC of  ≥ 56.6 mg SrS/L is considered in the CSA.