Registration Dossier

Ecotoxicological information

Toxicity to microorganisms

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Link to relevant study record(s)

Description of key information

The following study was submitted to address the endpoint Toxicity to Microorganisms on the structural analogue DBTO:
Clarke, N (2010) ASSESSMENT OF THE INHIBITORY EFFECT ON THE RESPIRATION OF ACTIVATED SEWAGE SLUDGE. Testing Laboratory: Harlan Laboratories Ltd, Shardlow Business Park, London Road, Shardlow, Derbyshire, DE72 2GD, UK. Owner company: Organo Tin REACH Consortium, c/o ReachCentrum, Avenue E. Van Nieuwenhuyse 6, B-1160, Brussels, BELGIUM. Report No. 3109/0024. Report date: 2010-05-21
The study was performed on the test material dibutyltin oxide. The study was assigned a reliability score of 1.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L

Additional information

The study data available for the registrant have been conducted on the structurally analogous substance DBTO. The study Clarke N (2010) was performed in accordance with the OECD guideline 209 and in compliance with GLP. The study was therefore assigned a reliability score of 1 and considered adequate for assessment. Activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 10, 32, 100, 320 and 1000 mg/l for a period of 3 hours at a temperature of 21 ± 1°C with the addition of a synthetic sewage as a respiratory substrate.

The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol.

The effect of the test item on the respiration of activated sewage sludge gave a 3-hour EC50 of greater than 1000 mg/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 44 mg/l.

It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg/l.

The reference item gave a 3-hour EC50 value of 8.6 mg/l, 95% confidence limits 6.7 - 11 mg/l.