Ammonium (xylenes and 4-ethylbenzene)sulfonates

Biodegradation in water: screening tests

Description of key information

Readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The HYDROTOPES Category comprises the following 6 substances:
STS - Sodium toluene 4-sulphonate (CAS 657-84-1, EC 211-522-5)
SXS - Sodium (xylenes and 4-ethylbenzene) sulphonate (EC 701-037-1)
NH4XS - Ammonium (xylenes and 4-ethylbenzene) sulphonate (EC 943-024-5)
SCS - Sodium p-cumenesulphonate (CAS 15763-76-5, EC 239-854-6)
KCS - Potassium p-cumenesulphonate (CAS 164524-02-1, EC 629-764-9)
NH4CS - Ammonium p-cumenesulphonate (CAS 680972-33-2, EC 811-484-5) 
In addition CaXS (Calcium Xylenesulphonate, CAS 28088-63-3, EC 248-829-9) was evaluated for complete the assessment despite it is not registered under REACH.

The biodegradability has been tested at least for each member of the Hydrotropes subgroup (toluene, xylene and cumene).

All the results are consistent and show that the substances are readily biodegradable.

One test is available on SXS (Hydrotropes Consortium, 2020).The ready biodegradability of the test item was determined with a non-adapted activated sludge over a test period of 28 days in the Modified Sturm Test, following OECD 301B. Both test item replicates reached the 60 % pass level within 11 days. The mean biodegradation on day 28 was 98 %. The 10-day window was fulfilled.

One test is available on STS (Sasol, 2004). The ready biodegradability of the test item was determined with a non-adapted activated sludge over a test period of 28 days in the Modified Sturm Test, following OECD 301B . The test substance showed complete degradation with a mean value of 99.8%. and the 10-day window was met. Under the test conditions the test item is readily biodegradable with the 28 day period of the study.

One test is available on SCS (Ruetgers-Nease Chemical Company, Inc, 1992). The ready biodegradability of the test item was determined with a mixed microbial inoculum by performing a semi-continuos activated sludge (SCAS) acclimation to the study, over a test period of 28 days in the Modified Sturm Test, following OECD 301B. Under the test conditions the test item is readily biodegradable with the 28 day period of the study. Anyway, this test was considered not adequate since there are some deficiencies, but the results can be considered consistent within the category and therefore it can be used as supporting in the whole hydrotropes category.

Moreover, other studies are available, and even if they have some deficiencies, their results are consistent with the new tests. Therefore, they can be used to support and strengthen the ready biodegradability of Hydrotropes category.

Two tests are also available on SXS, following 301B (Stepan, 1993; Ruetgers-Nease Chemical Company, 1992). Both tests have some deficiencies but the results confirm that the substance is readily biodegradable.

One test is available on SCS, following 301B (Ruetgers-Nease Chemical Company, Inc, 1992). The test has some deficiencies but the results confirm that the substance is readily biodegradable.

One test is available on CaXS, following 301B (Ruetgers-Nease Chemical Company, Inc, 1994). The test has some deficiencies but the results confirm that the substance is readily biodegradable.

For SCS and SXS one study following OECD 301D is available to assess the biodegradability.  It seems  that the measurement of oxygen consumption have some interferences which can result in a questionable result. Anyway, the studies are really poor and there are not enough details for a reliable assessment.

The chemical reactivity of the different counter ions is not expected to significantly influence the physical and chemical behaviour of the compounds with regard to environmental fate, eco-toxicity and mammalian toxicity. The presence of one or two methyl groups or a methylethyl group on the benzene ring is not expected to have a significant influence on chemical reactivity.

In addition, the OECD SIDS Report (2006) for the hydrotropes category concluded that “studies across the hydrotropes category demonstrate rapid and complete biodegradation under aerobic conditions and the Hydrotropes are considered to be readily biodegradable according to OECD criteria”. The OECD SIDS Report conclusion supports the experimental evidence provided.

Across the hydrotropes category, biodegradation results are consistent across the toluene, xylene and cumene sulfonates and their various salts. All results consistently indicate evidence for a ready biodegradation for Hydrotropes category members.