4,4'-isopropylidenebis[2-allylphenol]

Toxicity to aquatic algae and cyanobacteria

Description of key information

Determination of the effect of TK 11907 on the growth of the green alga Pseukirchneriella subcapitata.

Key value for chemical safety assessment

EC50 for freshwater algae:

1.4 mg/L

EC10 or NOEC for freshwater algae:

0.11 mg/L

Additional information

The study was performed to assess the effect of the test item on the growth of the green algaPseudokirchneriella subcapitata. The method followed that described in the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Regulation (EC) No 761/2009.

 

Methods:

Information provided by the Sponsor indicated the test item was practically insoluble in water.

 

Preliminary solubility work conducted indicated that it was not possible to obtain a testable solution of the test item using traditional methods of preparation e.g. ultrasonication and high shear mixing.

 

A preliminary media preparation trial indicated that a dissolved test item concentration of approximately 7.7 mg/L was obtained from a saturated solution method of preparation indicating this to be the limit of water solubility of this item under test conditions.

 

Following a preliminary range-finding test,Pseudokirchneriella subcapitatawas exposed to solutions of the test item at nominal concentrations of 0.32, 1.0, 3.2, 10 and 32% v/v saturated solution (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1 °C. The test item solutions were prepared by stirring an excess (50 mg/L) of test item in culture medium using a propeller stirrer at approximately 1500 rpm for 24 hours. After the stirring period any undissolved test item was removed by filtration (0.2 µm Sartorius Sartopore filter, first approximate 2 liters discarded in order to pre-condition the filter) to produce a 100% v/v saturated solution of the test item. This saturated solution was then further diluted as necessary, to provide the remaining test groups. Due to the potentially light sensitive nature of the test item, all test item preparation was performed under laboratory safety lighting/shielded from the light.

 

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter^®Multisizer Particle Counter.

 

Results:.

Analysis of the test preparations at 0 hours showed measured test concentrations to range from 0.018 to 1.5 mg/L. A decline in measured test concentration was observed at 72 hours in the range of less than the limit of quantification (LOQ) of the analytical method employed, determined to be 0.0054 mg/L, to 1.1 mg/L. Analysis of samples at 72 hours which had been prepared with the omission of algal cells showed measured test concentrations to range from 0.0070 to 1.3 mg/L (40% to 91% of the 0-Hour measured test concentrations). These results indicated that the test item was unstable over the test period and was adsorbing to the algal cells present. 

 

Given this it was considered appropriate to calculate the geometric mean measured test concentrations based on the 0-Hour measured test concentrations and those at 72 hours where no algal cells were present as this represents the actual test concentrations to which the algae were exposed.

 

Exposure ofPseudokirchneriella subcapitatato the test item gave the following results based on the geometric mean measured test concentrations:

 

Response Variable	EC50(mg/L)	95% Confidence Limits (mg/L)			No Observed Effect Concentration (NOEC) (mg/L)	Lowest Observed Effect Concentration (LOEC) (mg/L)
Growth Rate	1.4		*		0.11	0.36
Yield	0.20	0.16	-	0.24	0.045	0.11

 

*It was not possible to calculate 95% confidence limits for th