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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

EC 50 = 650 mg/L

Key value for chemical safety assessment

EC50 for microorganisms:
650 mg/L
EC10 or NOEC for microorganisms:
156 mg/L

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)

The microbial toxicity in the activated sludge was assessed wirth availbale studies bot on ASA and related salt (Hydrotropes category). Hydrotropes are completely dissociated in water and could be used in read across for the related acid form.

In addition, the two studies on Hydrotropes showed the same results and the EC10 value used for the assessment is > 1000 mg/L.
One study is a respiration inhibition test carried out using activated sludge and the test substance sodium p-cumenesulphonate in accordance with OECD Guideline No. 209. The test was performed under static conditions with the limit concentration 1000 mg a.i./L, corresponding to 2500 mg test item/L. The respiration rates of the control, reference and test substance replicates were measured after a contact time of three hours and the inhibitory effects of the test and reference item were determined in comparison to the control respiration rates. No inhibition was observed for the test substance corresponding to an EC10 of >= 1000 mg a.i./L. The second study (Fiebig, 2009) was undertaken at the same time by the same laboratory using the same protocol, but using the test substance sodium toluene 4-sulphonate. The 3-hour EC10 (and NOEC) was >=1000 mg/L active substance (nominal); the only concentration tested. These studies indicate that of the Hydrotropes substances are comparable in term of effects on microorganisms and show low toxicity to the microorganisms involved in sewage treatment processes. These studies indicate that the Hydrotropes substances are comparable in term of effects on aquatic invertebrates and show low toxicity.

It can be concluded that all members of the ASA category can be considered as non-toxic towards micro-organism in the activated sludge test.