N,N-dibutylbutan-1-aminium bis[2-(hydroxy-kO)benzoato(2-)-kO]borate(1-)

Toxicity to aquatic algae and cyanobacteria

Description of key information

After 72 hours of exposure of the unicellular green alga Pseudokirchneriella subcapitata to SABoTBA, the  ErC50 and EyC50, based on mean measured concentrations, were >28.9 mg/L (14% inhibition) and 28.2 mg/L, respectively.
The no observed effect concentration (NOEC) at 72 hours for growth rate and yield was 7.56 mg/L, and the lowest observed effect concentration (LOEC) was 28.9 mg/L based on mean measured concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:

28.9 mg/L

EC10 or NOEC for freshwater algae:

7.56 mg/L

Additional information

The effect of SABoTBA on the growth of the unicellular green alga Pseudokirchneriella subcapitata was assessed under non-axenic conditions.

The study was conducted in accordance with EC Methods for Determination of Ecotoxicity, Annex IV to Commission Regulation (EC) No 761/2009 Part C, Method 3 “Freshwater Algae and Cyanobacteria, Growth Inhibition Test” and Procedure 201 of the “Guidelines for Testing of Chemicals” of the Organisation for Economic Co-operation and Development: Freshwater Alga and Cyanobacteria, Growth Inhibition Test” (2006, corrected 2011).

Triplicate algal cultures, with an initial cell density of ca. 1 x 10⁴/mL, were exposed to SABoTBA dissolved in algal nutrient medium at nominal concentrations of 0.008, 0.030, 0.080, 0.260, 0.820, 2.64, 8.44 and 27.0 mg/L. The test media were prepared in OECD medium from an aqueous stock solution, which was made by the direct addition of the test substance to the dilution medium. The cultures were incubated in an orbital incubator under continuousp illumination at temperatures ranging from 21.4 to 23.0°C for 72 hours. 

At the start of the test, the measured levels of SABoTBA in samples of the test cultures ranged between 88 and 113% of their nominal values. After 72 hours, the measured levels ranged between 60 and 102% of their nominal values (between 59 and 90% of their starting values). The greatest losses were observed at the lower test concentrations.  Based on the geometric mean, the overall measured levels of SABoTBA were 0.00668, 0.0221, 0.0589, 0.212, 0.719, 2.39, 7.56 and 28.9 mg/L. These values were used in the calculation of study end-points.

Cell numbers were counted daily to monitor growth. The test results are expressed in terms of the growth rate and yield. The following values were derived from the data:

Parameter	Endpoint 72 hours	SABoTBA  (mg/L)
Growth rate	EC10	25.8 [25.5 & 28.3]
	EC50	> 28.9 [14% inhibition]
	NOEC	7.56
	LOEC	28.9
Yield	EC10	9.69 [7.91 & 11.1$]
	EC50	28.2 [25.8 & 31.2$]
	NOEC	7.56
	LOEC	28.9
[ ]           95% confidence limits $             Confidence interval may be unreliable due to goodness of curve fit NOEC   No observed effect concentration LOEC    Lowest observed effect concentration