Sodium N-chlorobenzenesulphonamide

Toxicity to microorganisms

Description of key information

The substance CAS 127-52-6 causes inhibitory effects on micro-organisms as contained in activated sludge of a municipal STP at the following ECX valuesEC20:   45.3 mg/L (95% confidence interval: 12.9– 78.8 mg/L ); EC50:  165 mg/L   (95% confidence interval: 98.9 – 313 mg/L ); EC80:  598 mg/L  (95% confidence interval: 314 – 3010 mg/L ). The EC50 is about 12 times lower than that of reference substance 3,5-dichlorophenol. A supporting experiment was conducted similarly to the key study. At a test concentration of 10 mg/L, the test substance causes 1% inhibition, whereas a test concentration of 1000 mg/L caused 96.2% inhibition. Chromatographic analyses of deionised water and test media during the study are considered not reliable. Reasons are provided below.

Key value for chemical safety assessment

EC50 for microorganisms:

165 mg/L

EC10 or NOEC for microorganisms:

10 mg/L

Additional information

Discussion of results.

For the following reasons, the chromatographic results obtained during the study are considered not reliable:

·        The applied HPLC method is not validated for OECD 209 media. Though the HPLC method presented in Chapter 8 validates daphnia and algae medium, besides deionised water, the medium which is suitable to conduct OECD 209 studies is not comparable with any of the validated matrices, due to its high content of proteines (peptone, meat extract), urea and salts.

·        The HPLC method is not validated for benzenesulfonamid, the dechlorinated CAS 127-52-6.

·        Day 0 analyses or similar QC samples are not available.

·        50% of the test substance was decomposed in deionised water within 3 days (one test group). The substance is stable at pH 7 and the DT-50 at pH 4 (should the pH of deionised water be that low) is at least 25 days, based on a valid Hydrolysis study according to OECD 111.

·        The filtration method of sludge containing samples is not validated.