p-cumenesulphonic acid

Endpoint summary

Additional information

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.. 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.

A single, good quality (non-GLP) fish acute toxicity study (Hoechst, 1981), is available for p-toluenesulfonic acid (CAS No. 104-15-4). There were no mortalities and the 96 hr LC50 is >325 mg active ingredient/L.

There are 3 acute studies with the invertebrate Daphnia magna. The key study is an OECD 202 Guideline, GLP-compliant study (p-TA Coalition, 2005) with benzenesulfonic acid (CAS No. 98-11-3). It is a well documented limit test with analytical confirmation. There was no mortality or immobility observed at 100 mg/L (nominal) / 103 mg/L (measured). The test conditions were confirmed to be valid and the reference substance produced expected results. The 48h-EC50 is reported as >100 mg active ingredient/L. A second study with 98-11-3 (Huntsman, 1995) and a study with toluene-4-sulphonic acid (CAS No. 104-15-4) (Hoechst, 1983) confirm the lack of toxicity at 100 mg/L.

There is one algal toxicity study. It is an OECD 201 Guideline, GLP compliant study for benzenesulphonic acid (CAS 98 -11 -3) (pTA-Coalition, 2005) using analytical confirmation and a reference substance. The 72h-EC50 for Selenastrum capricornutum was 70 mg/L active ingredient based on biomass inhibition and 73 mg/L a.i. for growth rate inhibition. The reported 72h-NOEC was 44.8 mg/L. The report indicates that the observed toxicity may very well have been due to the acidity of the test substance. The pH of the test medium at the two highest test concentrations (100 and 220 mg/L) was in the range of 5 and 3, respectively. Comparable tests with the salt form (hydrotropes - calcium xylene sulphonate - Ruetgers Nease, 1994; and sodium xylene sulphonate - Stepan, 1993) indicate much higher EC50 values, >758 mg/L a.i. and >230 mg/L a.i., respectively.

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 580 mg/L.

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.