Naphthalenesulfonic acid, di-C9-rich C8-10-branched alkyl derivs., barium salts

Endpoint summary

Description of key information

The short-term tests for aquatic toxicity at three trophic levels were performed on the free acid DNNSA and partly also on the barium salt, supporting the findings of no acute toxicity within limits of water solubility. The results on the free acid DNNSA are reported here as surrogate for the barium salt:

Based on a short-term toxicity test result to fish, the 96h-LC50 was beyond the range tested, i.e. exceeded the highest average exposure concentration of 0.28 mg/l. This was considered to correspond to the maximum soluble concentration in test medium. Therefore, under the test conditions, and given the solubility characteristics of the test material, neither the 96h-LC50 or a level causing any observable effect can be attained.

An Acute Toxicity Study in Daphnia magna was conducted with test substance DNNSA based on OECD TG 202. Twenty daphnids per group (5 per vessel, 4 vessels) were exposed to a control and WAFs prepared at loading rates of 4.6, 10, 22, 46 and 100 mg/l in the final test. Total exposure time was 48 hours and samples for analytical confirmation of the exposure concentrations were taken at the start and at the end of the test. Analysis of the samples taken at the start of the final test showed measured concentrations being highly variable and not directly related to the applied loading rates. Therefore, the effect parameters were expressed in terms of average exposure concentration. The highest average exposure concentration was measured in the WAF prepared at 10 mg/l and corresponded to 0.27 mg/l. The study met the acceptability criteria prescribed by the protocol and was considered valid. For Daphnia magna exposed to the test substance the 48h-EC50 was beyond the range tested, i.e. exceeded the average exposure concentration of 0.27 mg/l. Due to the very low solubility of di C8-C10, branched, C9 rich, alkylnaphthalene sulphonic acid (DNNSA) in test medium, concentrations that might be toxic to Daphnia magna could not be reached. The effects observed at the higher measured concentrations of the test substance were mechanical rather than toxic.

A Fresh Water Algal Growth Inhibition Test was conducted for the test substance with Pseudokirchneriella subcapitata. The study procedures were based on the OECD guideline No. 201, 2006; Annex 5 corrected 28 July 2011. Under the conditions of the DNNSA study with Pseudokirchneriella subcapitata, reduced growth rate of this fresh water algae species significantly at a TWA concentration of 0.30 mg/l and higher. The EC50 for growth rate reduction (ERC50: 0-72h) was beyond the range tested, i.e. exceeded a TWA concentration of 1.2 mg/l. The lowest EC10 in this study is for cell number (yield) which is 0.20 mg/L and the EC10 for growth rate is 0.80 mg/L.

Under the conditions of an OECD 209 test di C8-C10, branched, C9 rich, alkylnaphthalene sulphonic acid (DNNSA) was not toxic to waste water (activated sludge) bacteria at or below a loading rate of 110 mg/l (NOEC). DNNSA is the major component in BARIUM BIS( DI C8-C10, BRANCHED, C9 RICH, ALKYLNAPHTHALENE SULPHONATE) (Barium DNNSA) and therefore it can be concluded that Barium DNNSA is not toxic to waste water bacteria too.

In order to confirm the validity of the read-across approach, an acute study in daphnia magna with the barium salt of DNNSA was performed, which confirmed the hypothesis above that no toxicity was observed at the highest tested concentration of 100 mg/L nominal (EC50 > 0.18 mg/L analytically determined). This value is used as starting point for hazard and risk assessment in a worst case approach.