Sodium long chain alkyl salicylate

Toxicity to aquatic algae and cyanobacteria

Description of key information

72 h ErC50 0.89 mg/L (95 % CL 0.57 to 1.37 mg/L), 72 h EyC50 0.25 mg/L (95 % CL 0.11 to 0.91 mg/L) and 72 h NOEC (growth and yield) 0.27 mg/L (Pseudokirchneriella subcapitata), OECD 201, EU Method C.3 and OECD 23.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.89 mg/L

EC10 or NOEC for freshwater algae:

0.27 mg/L

Additional information

In the key study, the toxicity of the test material to the freshwater green alga Pseudokirchneriella subcapitata was investigated in accordance with the standardised guidelines OECD 201, EU Method C.3 and OECD 23 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 batch of test material tested was not completely soluble in test medium at the initial loading rate prepared. Preparation of test solutions started with a loading rate of 100 mg/L, applying two days of magnetic stirring to ensure maximum dissolution of the test material in the test medium was reached. The resulting dispersion was filtered through a 0.20 µm membrane filter. The resulting Water Soluble Fraction (WSF) was used as the highest test concentration and used to prepare the lower test concentrations by subsequent dilution in test medium.

A final EC50 test was performed based on the result obtained in a preceding preliminary test. Six exponentially growing algal cultures were exposed to an untreated control, whereas three replicates per group were exposed to 1.0, 3.2, 10, 32 and 100 % of a WSF prepared at a loading rate of 100 mg/L. The initial cell density was 104 cells/mL. The total exposure period was 72 hours and samples for analytical confirmation of actual exposure concentrations were taken at the start, after 24 and 72 hours of exposure.

The measured concentration in the undiluted WSF at the start of the test was 25.5 mg/L. The measured concentrations in the lower test groups were in agreement with the respective dilution factors. During the test period a slight decrease in concentrations was generally observed for the high test groups and a more prominent decrease for the lower test groups. Based on these results, the Time Weighted Average (TWA) exposure concentrations were calculated. The range tested based on TWA concentrations corresponded with 0.09, 0.27, 2.0, 5.5 and 23 mg/L.

Growth rates were increasingly inhibited with increasing concentration. The percentage inhibition ranged between 6.7 and 90 %. Statistically significant inhibition of growth rate was found at TWA concentrations of 2.0 mg/L and higher.

Inhibition of yield also increased with increasing concentration resulting in more than 99 % inhibition at and above a TWA concentration of 5.5 mg/L. Statistically significant inhibition of yield was found at TWA concentrations of 2.0 mg/L and higher.

Microscopic observations at the end of the test revealed a normal and healthy appearance of the exposed cells when compared to the control.

The study generally met the acceptability criteria and was considered valid.

Under the conditions of this study, the 72 h ErC50 was 0.89 mg/L (95 % CL 0.57 to 1.37 mg/L), the 72 h EyC50 was 0.25 mg/L (95 % CL 0.11 to 0.91 mg/L) and the 72 h NOEC for both growth and yield was 0.27 mg/L.

Further information is available in the form of a disregarded study. The test was carried out using methodology similar to that outlined in the standardised guideline OECD 201 under GLP conditions, however there were shortcomings. The test material was not wholly soluble in water and was used as an homogeneous emulsion. There was no attempt to remove impurities such as xylene and no analysis of test material levels took place during the study. Effects are considered likely to be the result of physical contact with oil droplets combined with toxicity of impurities. The study was awarded a reliability score of 3 in accordance with the principles for assessing data quality set forth by Klimisch et al. (1997).

Selenastrum capricornutum was exposed to the test material for 96 hours. The 96 h EC50 based on Chlorophyll A determinations on day 4 was estimated to be 2.1 mg/L.