Potassium hydrogensulphate

Short-term toxicity to aquatic invertebrates

Description of key information

The basis for the read-across concept for this project is the equilibrium between sulfates, hydrogensulfates, and sulfuric acid in aqueous solutions depending on pH value which is clearly described in published literature and summarised in the following equations:

H₂SO₄<-> HSO₄^-+ H⁺      HSO₄^-<-> H⁺+ SO₄^2-

As the nature of the cation should make no significant difference in this case concerning toxicity and solubility (all compounds are very soluble in water), only the chemical and biological properties of the anion are considered relevant. Based on the described equilibrium correlations, we propose unrestricted read-across between the groups of sulfates, hydrogensulfates and sulfuric acid concerning systemic toxicity.

Sodium sulfate is not toxic to D. magna, the lowest LC50 found  in a water hardness of 25 mg CaCO3/l and Ca:Mg ratio of 0.7 is 1766 mg/l. Under standard test conditions sodium sulfate is even less toxic, LC50 found there is 4736 mg/l.      

The test was found to be valid with restrictions because the study was well conducted with standard guidelines and chemical analysis. No GLP no analytical certificates and no raw data were documented. It is not known whether nominal or measured concentrations were used for the results. Sodium sulfate is stable in water over a period of 48h, therefore it is considered not to have an impact on the outcome and the conclusions of the test.

Read-across from sodium sulfate to potassium hydrogensulfate is considered justified. Therefore it can be concluded that potassium hydrogensulfate has no acute toxic properties to aquatic invertebrates.          

Additional information

The basis for the read-across concept for this project is the equilibrium between sulfates, hydrogensulfates, and sulfuric acid in aqueous solutions depending on pH value which is clearly described in published literature and summarised in the following equations:

H₂SO₄<-> HSO₄^-+ H⁺      HSO₄^-<-> H⁺+ SO₄^2-

As the nature of the cation should make no significant difference in this case concerning toxicity and solubility (all compounds are very soluble in water), only the chemical and biological properties of the anion are considered relevant. Based on the described equilibrium correlations, we propose unrestricted read-across between the groups of sulfates, hydrogensulfates and sulfuric acid concerning systemic toxicity.

Many publications are available on short-term toxicity of sodium sulfate to invertebrates, but most were not found reliable.

Four publications which describe six short-term tests were found reliable with restrictions. Mount (1997) performed two tests, one with Daphnia magna and one with Ceriodaphnia dubia. Soucek and Kennedy (2005) described two tests, one with Ceriodaphnia dubia and one with Sphaerium simile. Soucek (2007) performed a test with Ceriodaphnia dubia. Davies and Hall (2007) performed tests with Daphnia magna. None of these tests were performed under GLP, but they were all according to EPA guidelines with chemical analyses. Davies and Hall performed tests at several water hardness levels and 3 Ca:Mg ratios. The toxicity of sodium sulfate decreased with increasing water hardness. At a water hardness of 25 mg CaCO3/l and a Ca:Mg ratio of 0.7 the LC50 was 1766 mg/l. Under standard conditions the LC50 was 4736 mg/L.

Read-across from sodium sulfate to potassium hydrogensulfate is considered justified. Therefore it can be concluded that potassium hydrogensulfate has no acute toxic properties to aquatic invertebrates.