Registration Dossier

Diss Factsheets

Ecotoxicological information

Toxicity to microorganisms

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

The 3-hr EC50 to activated sludge was 550 mg/L for a C11.6 Na-linear sodium alkyl sulfonate.

Key value for chemical safety assessment

EC50 for microorganisms:
550 mg/L

Additional information

No specific studies on Benzenesulfonic acid, mono-C11-13-branched alkyl derivs (BABS Acid) were available. However, a study is available on analogue substance linear alkylbenzene sulfonic acid, sodium salt, or LAS. The LAS structure is a C10 to C13 linear alkyl chain with a para-substituted benzene sulfonic acid sodium salt group attached at any of the secondary alkyl chain carbon positions. The alkyl chain length averages 11.6. LAS is structurally similar to BABS Acid, as both are para C11 -C13 alkylbenzene sulfates. The primary difference is whether the alkyl chain is linear or branched and presence of Sodium Cation.

Based on well accepted principles of modeling (D.W. Roberts, Sci. Total Environ. 109/110: 557 -68, 1991), linear structures are more toxic than brached structures of the same carbon chain number. This principle is supported by the results of acute toxicity studies of fish and algae, including five direct comparison of activities while a single Daphnia toxicity is an exception to this pattern. Based on structural similarities, accepted principles of modeling and the weight of evidence from acute aquatic toxicity testing, LAS is a good analogue for read-across for instances where data are available on it but not on BABS Acid.

The purpose of the LAS study was to determine the toxicity of three commercial LAS products to the activated sludge of a treatment plant basically operating on domestic sewage. A contact time of 3 hours instead of 15 minutes was chosen to better simulate the real residence time used in wastewater treatment plants (4-6 hours). The EC50values are far above maximum raw sewage concentrations of 6 -8 mg/L and therefore provide a high margin of safety. 

Based on the data for linear and branched alkylbenzene sulfonates, linear structures are more toxic than branched structures. Therefore, data on linear materials, e.g., the chronic aquatic studies using LAS, are considered to be a worst case scenario.