Sodium hydrogensulphate

Endpoint summary

Additional information

Sodium hydrogensulfate:

Fish usually tolerate a pH range of 6-9. Most data are available on the tolerance of fish to acid pH values. A pH range of 5-6 may become lethal, as an acid discharge may liberate sufficient carbon dioxide from bicarbonate in the water either to be directly toxic, or to cause the pH range of 5-6 to become lethal. Below a pH value of 5, mortalities may be expected for many species, although some species may be acclimated to pH values as low as around 4 (Alabaster and Lloyd, 1980). The fish Umbra pygmaea, which is indigenous in North-America, can tolerate a pH value as low as 3. This fish species has been introduced in the Netherlands in the past and is the only fish species that lives in acid bogs (OVB, 2002).

Sodium sulfate:

Many publications were found on short-term toxicity of sodium sulfate to aquatic organisms.

Only one study with fish was reliable with restrictions, Mount et al.(1997). The study was performed according to EPA guideline and with determination of test substance concentrations. It was not performed under GLP.

Pimephales promelas was exposed to a range of sodium sulfate concentrations in reconstituted water. Fish appeared to be the least sensitive with an LC50 of 7960 mg/l.

Many publications are available on short-term toxicity of sodium sulfate to invertebrates.

The key study, performed by Davies and Hall (2007) was with Daphnia magna. The tests were were considered valid with restrictions. 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, this was the lowest value found. Under standard conditions the LC50 was 4736 mg/L.

No valid studies with algae were found. Patrick et al. (1968) performed a 120-hour growth test with Nitzschia linearis. The test duration of 120 hours and the tested species N. linearisis different than recommended in the guideline. The reference test data are comparable to that of data for OECD approved algae species. The response of the tested diatom species is therefore likely to be similar to approved test species. Due to the very low toxicity of sodium sulfate in all ecotoxicological endpoints this study described by Patrick et al., can be used with care. An EC50 value of 1900 mg/l was found. This result shows that sodium sulfate is not a substance of concern for algae.

Tokuz and Eckenfelder (1979) and Tokuz (1986) found that the increasing concentrations of sodium sulfate did not cause any appreciable deterioration in effluent quality in terms of effluent suspended solids and COD. The eflluent COD stayed more or less at a constant level and suspended solids concentration increased slightly. The rate of increase of salinity was much faster for the sodium sulfate system but no negative effects were seen. Effects were measured by the efficiency of DOC removal. There was no effect on the microorganisms up to approximately 8 g/l over a period of 37 days. With respect to the high NOEC values, sodium sulfate is not expected to be hazardous for activated sludge. This study was also found valid with restrictions.

One long-term result was found for invertebrates (Soucek, 2007), this study was considered valid with restrictions. The LOEC for reproduction of Ceriodaphnia dubia was 1329 mg/l, which was the lowest result obtained in this test. The NOEC (taken from a graph) is approx. 1109 mg/l.

Overall it can be concluded that sodium sulfate has no acute adverse effect on aquatic organisms. The long-term result shows that there is no concern either.

Read-across from sodium sulfate to sodium hydrogensulfate is considered justified. Threfore it can be concluded that sodium hydrogensulfate has no acute adverse effects as well as long-term eefects on aquatic organisms.