Reaction mass of sodium hydrogensulfide and sodium carbonate

Short-term toxicity to aquatic invertebrates

Description of key information

For H2S toxicity, two key studies were identified. The key study for freshwater aquatic invertebrates is the study of Oseid and Smith (1974a) and that for marine aquatic invertebrates is the study of Gopakumar and Kuttyamma (1996). Oseid and Smith (1974a) obtained a 96-h LC50 of 0.02 mg H2S/L for mayfly larvae of the species Baetis vagans. Gopakumar and Kuttyamma (1996) reported a 96-h LC50 of 0.032 mg H2S/L for the penaeid prawn Penaeus indicus. For sulfate toxicity, the study of Mount et al. (1997) was identified as a key study. This study reports a 48-h LC50 of 3080 mg Na2SO4/L for Ceriodaphnia dubia. This value can be recalculated to an LC50 of 2083 mg SO4 2-/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.02 mg/L

Marine water invertebrates

Marine water invertebrates

Effect concentration:

0.032 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 Oseid and Smith (1974a) yielded the lowest reliable 96-h LC50 for freshwater aquatic invertebrates (larvae of the mayfly Beatis vagans), whereas the study of Gopakumar and Kuttyamma (1996) reported the lowest reliable 96-h LC50 for marine invertebrates (the penaeid prawn Penaeus indicus). These values will be used for derivation of a PNECaquatic for H₂S for the freshwater and marine environment. 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, one reliable (Klimisch 2) study was selected for inclusion in this dossier (Mount et al., 1997). This study reports a 48-h LC50 of 3080 mg Na₂SO₄/L for Ceriodaphnia dubia, yielding a 48-h LC50 of 2083 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 NaOH and Na₂CO₃, one reliable (Klimisch 2) marine study were found for each. For Na₂CO₃, Warne and Schifko (1999) reported a 48 -h EC50 for Ceriodaphnia sp. between 200 and 227 mg/L. For NaOH, Warne (1999) reported a 48 -h EC50 for Ceriodaphnia sp. of ca. 40.4 mg/L. No freshwater data were found.