Hexadecyl acetate

Toxicity to aquatic algae and cyanobacteria

Description of key information

Using a method designed to avoid over-saturation of test media, no toxic effects were observed when Pseudokirchneriella subcapitata were exposed to a saturated solution obtained from an initial loading rate of 1.0 mg/L test material (OECD 201 and EU Method C.3)

Additional information

KEY STUDY

GUIDELINE

A study was performed to assess the effect of the test item on the growth of the green alga Pseudokirchneriella subcapitata. The method followed that decribed 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 water solubility of the test item was less than 0.0114 mg/L. As such, given the pure nature of the test item, a saturated solution method of preparation (initial loading rate 1.0 mg/L) was considered most appropriate for the test material in order to ensure that over saturation of the media did not occur.

Following preliminary range-finding tests,Pseudokirchneriella subcapitatawas exposed to a solution of the test item at nominal concentrations of 6.25, 12.5, 25, 50, 75 and 100 % v/v saturated solution for 72 hours under constant illumination and shaking at a temperature of 24 ± 1 °C (three replicate flasks per concentration).

Test item solutions were prepared by stirring an excess (1.0 mg/L) of test item in culture medium using a propeller stirrer at approximately 1500 rpm for 48 hours. After the stirring period any undissolved test item was removed by filtration (0.2μm Sartorius Sartopore filter, first approximate 2 L discarded in order to pre-condition the filter) to produce 100 % v/v saturated solution of the test item. This saturated solution was then further diluted as necessary.

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 and 72 hours showed measured test concentrations of less than the limit of quantification (LQQ) of the analytical method employed. This does not infer that no test item was in solution, just that any dissolved test item present was at a concentration of less than the LQQ of 0.012 mg/L.

Exposure of Pseudokirchneriella subcapitata to the test item gave EC50 values of greater than 100 % v/v saturated solution. The No Observed Effect Concentration was determined to be 100 % saturated solution.

CONCLUSION

The study showed that there were no toxic effects when Pseudokirchneriella subcapitata were exposed to a saturated solution obtained from an initial loading rate of 1.0 mg/L test material.

SUPPORTING STUDY

GUIDELINE

 

A study was performed to assess the effect of the test item on the growth of the green algaPseudokirchneriella subcapitata. The method was designed to be compatible with 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) 761/2009.

 

METHODS

 

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

 

A preliminary media preparation trial indicated that a dissolved test item concentration of approximately 0.15 mg/L was obtained from a saturated solution method of preparation indicating this to be the limit of water solubility of the test item under test conditions.

 

Following a preliminary range-finding test and initial experiments, Pseudokirchneriella subcapitata was exposed to a solution of the test item at nominal concentrations of 6.25, 12.5, 25, 50 and 100 % v/v saturated solution (three replicate flasks) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1 °C.

 

The test item solution was prepared by stirring an excess (100 mg/L) of test item in culture medium using a propeller stirrer at approximately 1500 rpm for 48 hours. After the stirring period, any undissolved test item was removed by filtration (0.2 μm Sartorius Sartopore filter, first approximate 2 L 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.

 

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 0.03 to 0.44 mg/L. A decline in measured test concentration was observed at 72 hours to less than the limit of quantification (LOQ) of the analytical method employed, which was determined to be 0.0036 mg/L. Given this it was considered appropriate to calculate the results based on the geometric mean measured test concentrations to give a "worst case" analysis of the data.

 

CONCLUSION

 

Exposure of Pseudokirchneriella subcapitata to the test item gave an ErC50 (0 -72 h) of 0.027 mg/L . The No Observed Effect Concentration (NOEC) based on growth rate was 0.010 mg/L and the Lowest Observed Effect Concentration (LOEC) based on growth rate was 0.015 mg/L.

 

Exposure of Pseudokirchneriella subcapitata to the test item gave an EyC50 (0 -72 h) of 0.015 mg/L. The No Observed Effect Concentration (NOEC) based on yield was 0.010 mg/L and the Lowest Observed Effect Concentration (LOEC) based on yield was 0.015 mg/L.