Sodium long chain alkyl salicylate

Toxicity to microorganisms

Description of key information

 3 h EL50 >1000 mg/L, NOEL 460mg/L; OECD 209, EU Method C.11 and ISO Standard 8192 

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

460 mg/L

Additional information

In the key study, the potential for the test material to cause toxicity to activated sludge was investigated in a study conducted in accordance with the standardised guidelines OECD 209, EU Method C.11 and ISO Standard 8192 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the principles for assessing data quality set forth by Klimisch et al. (1997).

The influence of the test material on the respiration rate of activated sludge of a predominantly domestic sewage was investigated after a contact time of 3 hours.

The test material was not sufficiently soluble to allow the preparation of a 10 g/L stock solution in water. Therefore, test material and Milli-RO water mixtures were magnetically stirred for a period of 24.5 to 25.5 hours. Subsequently, synthetic medium, sludge and Milli-RO water were added resulting in the required loading rates. Optimal contact between the test material and test medium was ensured by applying continuous aeration and stirring during the 3-hour exposure period. Thereafter, oxygen consumption was recorded for approximately 10 minutes.

The final test was performed based on the result of a preceding combined limit/range-finding test. Five loading rates were tested at nominal concentrations of 46, 100, 220, 460 and 1000 mg/L. Five replicates per loading rate and six replicates for an untreated control group were tested.

No statistically significant inhibition of the respiration rate of the sludge was recorded at or below a loading rate of 460 mg per litre. At 1000 mg/L the inhibitory effect of the test material on aerobic waste water (activated sludge) bacteria was 30 %.

The EL10, EL20 and EL50 loading rates were 340, 810 and >1000 mg/L, respectively.

The batch of activated sludge was tested for sensitivity with the reference material 3,5-dichlorophenol and showed normal sensitivity. The study met the acceptability criteria and was considered valid.

Under the conditions of the study, the test material was not toxic to waste water bacteria (domestic activated sludge) at or below a loading rate of 460 mg/L (NOEL).

Supporting information is available in the form of a disregarded study that was conducted to investigate the inhibition of the growth of a pure culture of Pseudomonas fluorescens. The test material was present in mineral oil and administered as a water-leachate described as a dense emulsion. Accurate assessment of growth by optical density was not possible and analysis comprised dissolved organic carbon measurements, which are not selective for the test material. On this basis, the study was awarded a reliability score of 3 in accordance with the criteria set forth by Klimisch et al. (1997).

In the study, plate counts conducted after 5 hours showed that the water-leachate of the test material reduced cell numbers by 16 % compared to control inocula.