(xylenes and 4-ethylbenzene)sulfonic acids

Endpoint summary

Additional information

The ASA Category comprises the following 5 aromatic sulphonic acids:

 

TSA, Toluene-4-sulphonic acid (EC 203-180-0, CAS 104-15-4)

XSA, (Xylenes and 4-ethylbenzene) sulphonic acid (EC 701-247-3, CAS -) Former EC 246-839-8

CSA, p-cumene sulphonic acid (EC 240-210-1, CAS 16066-35-6)

BSA, Benzene sulphonic acid (EC 202-638-7, CAS 98-11-3)

HBSA, 4-hydroxybenzensulphonic acid (EC No. 202-691-6, CAS No. 98-67-9)

 

For all the three trophic levels valid studies are existing and the results are homogeneous and consistent along the whole category.

 

Algae have been tested on BSA and HBSA. For the other members the corresponding hydrotrope has been tested. The study on BSA has been selected as representative for the category, with an EC50 of 73 mg/L and a NOEC of 44 mg/L, since it is a good quality study, performed on a very pure substance. The two studies performed on acids have very similar results and the lower has been taken as conservative representative value. Results on the salt forms of STS, SCS and SXS demonstrated that the acid form is conservative towards the aquatic plants, being the EC50 values in general higher, but the NOEC has been found in two cases at the same level, between 30 and 40 mg/L, therefore all members of the category are well represented by the existing studies.

 

The Short-term toxicity testing on invertebrates has been tested on BSA, TSA and HBSA. In all cases EC50 48h was always > 100 mg/L. Further studies are available for the sodium salt of Toluene, Xylene and Cumene derivatives (Hydrotropes) and in all cases the EC50 48 h was higher than 100 mg/L. It can be concluded that for all the members of the category the representative result for EC50 48h on daphnia magna is > 100 mg/L

 

The short-term toxicity on fish has been tested on BSA TSA and HBSA, For XSA and CSA there are no studies available and the endpoint can be covered by the studies available on the corresponding salts.

No sign of toxicity have ever been recorded at any maximum tested concentration, ranging from 70 to 325 mg/L a.i.. Tests on fish have been performed taking into account the effects found in the algae toxicity study and using it as a limit value.

 

There is a single study of aquatic microbial toxicity (Hoechst, 1989). The OECD 209 guideline study with activated sludge microbes exposed to toluene-4-sulphonic acid (CAS. 104-15-4) reports a 3-hour NOEC for growth inhibition is 650 mg/L.

 

Algae are the most sensitive aquatic species with a 72-hr EC50 value of 73 mg/L a.i., and NOEC of 44.8 mg/L a.i. and this value will be taken as the reference for the acquatic toxicity Risk Assessment. Fish, invertebrates and bacteria appear much less sensitive. It may well be the acidity of the test substances that are the cause of the observed algal toxicity. The pH of the test medium was between 3 and 5 in the replicates at the end of the test. The pH in the fish, invertebrate and bacteria tests remained in the normal aquatic environment range. Toxicity in the sediment compartment is not considered a particularly relevant endpoint for these acids given their low partitioning coefficients.

 

The aromatic sulphonic acids have low logPow values and are therefore not expected to be sorbed onto sediments. These substances are readily biodegraded and therefore will not accumulate. A significant distribution into the sediment compartment is not predicted and exposures to sediment dwelling organisms is expected to be comparable to pelagic species.