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Ecotoxicological information

Short-term toxicity to fish

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Link to relevant study record(s)

Description of key information

For H2S toxicity, no reliable data were identified for marine fish. For freshwater fish, the study of Yusoff et al. (1998) was identified as key study. In this study, Javanese carp larvae (Puntius gonionotus) were exposed for 96 h in a flow-through system to a control treatment or a series of increasing sulfide concentrations. The test substance used was Na2S.9H2O. The resulting 96-h LC50 was 0.0027 mg H2S/L. For sulfate toxicity, the study of Mount et al. (1997) was identified as a key study. This study reports a 96-h LC50 of 7960 mg Na2SO4/L for fathead minnow (Pimephales promelas). This value can be recalculated to an LC50 of 5383 mg SO4 2-/L.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
0.003 mg/L

Additional information

Toxicity studies investigating the toxicity of Na2S or NaHS to aquatic organisms have focused in most cases on the toxicity of H2S, which is the most toxic sulfur species that can be formed upon dissolution of Na2S and NaHS. Among the available studies using either Na2S, NaHS (or its respective hydrates) or H2S as test substance, the study of Yusoff et al. (1998) yielded the lowest reliable 96-h LC50 for freshwater fish. No reliable data were identified for marine fish. The 96-h LC50 of 0.0027 mg H2S/L reported by Yusoff et al. (1998) for the Javanese carp Puntius gonionotus will be used in the aquatic hazard assessment for PNEC derivation for H2S. In oxic environments, released sulfides will be oxidized to - eventually - sulfate. In these cases, the risks entailed by the released sulfur should be evaluated using toxicity data for sulfate. Na2SO4 was identified as the most relevant substance for this purpose. From the OECD SIDS for Na2SO4, two reliable (Klimisch 2) studies were selected for inclusion in this dossier. The study of Mount et al. (1997) was considered as the key study. This study reports a 96-h LC50 of 7960 mg Na2SO4/L for fathead minnow (Pimephales promelas), yielding a 96-h LC50 of 5383 mg/L for sulfate. This LC50 most likely represents a worst case value since the overall observed toxicity of Na2SO4 is also affected by the presence of sodium ions and not only by the presence of sulfate ions.

For Na2CO3, two reliable (Klimisch 2) freshwater studies were found for inclusion. Cairns and Scheier (1959) reported the lowest 96 -h LC50, of 300 mg/L for bluegill sunfish (Lepomis macrochirus). For NaOH, no reliable studies were found, although two studies reporting Median Tolerance Limits are included in the dossier.