2,5-bis(1,1,3,3-tetramethylbutyl)hydroquinone

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 January 2018 to 08 March 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Reliable experimental study following OECD 201 guidelines (2006) and EC No. 761/2009 Method C.3 adopted 2009 and GLP standards.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

2009

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

The test was carried out using Pseudokirchneriella subcapitata strain CCAP 278/4. Liquid cultures of Pseudokirchneriella subcapitata were obtained from the Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland. Master cultures were maintained in the laboratory by the periodic replenishment of culture medium. The master cultures were maintained in the laboratory under constant agitation by orbital shaker (100 to 150 rpm) and constant illumination at 24 ±1 °C.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

24 °C ± 1 °C

pH:

7.5 – 8.6

Nominal and measured concentrations:

Based on the results of a preliminary range-finding test, the green alga was exposed to an aqueous solution of the test item at nominal concentrations of 6.25, 12.5, 25, 50 and 100 % v/v saturated solution (three replicate flasks per concentration).

Details on test conditions:

10 mg/L)

Reference substance (positive control):

yes

Remarks:

Potassium dichromate was the reference item in a study at concentrations of 0.25 mg/L, 0.50 mg/L, 1.0mg/L, 2.0 mg/L and 4.0 mg/L. The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: % v/v saturated soluition

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

100% v/v saturated solution prepared from a test solution with a loading rate of 10 mg/L.

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

Test solution prepared with a loading rate of 10 mg/L resulting in a 100% v/v saturation solution.

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

> 100 other: % v/v saturated solution

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

100% v/v saturated solution prepared from a test solution with a loading rate of 10 mg/L.

Duration:

72 h

Dose descriptor:

EL20

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

Test solution prepared with a loading rate of 10 mg/L resulting in a 100% v/v saturation solution.

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 100 other: % v/v saturated solution

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

100% v/v saturated solution prepared from a test solution with a loading rate of 10 mg/L.

Key result

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

Test solution prepared with a loading rate of 10 mg/L resulting in a 100% v/v saturation solution.

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

100 other: % v/v saturated solution

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

100% v/v saturated solution prepared from a test solution with a loading rate of 10 mg/L.

Duration:

72 h

Dose descriptor:

LOELR

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

Test solution prepared with a loading rate of 10 mg/L resulting in a 100% v/v saturation solution.

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

50 other: % v/v saturated solution

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

50% v/v saturated solution was a dilution of the initial test solution of 100% v/v saturated solution; the initial test solution was prepared with a loading rate of 10 mg/L.

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

Test solution was a dilution of the initial test solution; the initial test solution was prepared with a loading rate of 10 mg/L resulting in a 100% v/v saturation solution.

Results with reference substance (positive control):

The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

Reported statistics and error estimates:

One way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf, 1981) and Dunnett's multiple comparison procedure for comparing several treatments with a control (Dunnett, 1955) was carried out on the growth rate and yield data after 72 hours for the control and all test concentrations to determine any statistically significant differences between the test and control groups. All statistical analyses were performed using the SAS computer software package (SAS, 1999 - 2001).

Analysis of the 50% and 100% v/v saturated solution test preparations at 0 and 72 hours showed measured test concentrations of less than the LOQ (0.26 mg/L) of the analytical method. 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 LOQ.

Given that measurable levels of test item could not be detected in the test preparations, in accordance with the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (OECD 2000) results were calculated based on nominal test concentrations. Results were also calculated based on the initial loading rate of the 100% v/v saturated solution (10 mg/L).

Validity criteria fulfilled:

yes

Remarks:

Cell concentrations of control increased by a factor of 265 after 72 h (protocol ≥ factor of 16); mean of coeffi of var. for growth rates control 4% (protocol ≤ 35%); coeff. of var.of avg. sp.growth rate in replicate control cultures 3% (protocol ≤ 7%).

Conclusions:

The test substance did not cause a reduction of growth in a series of algal cultures (test units) exposed to the test item for 72 h; therefore, there were no toxic or inhibitory effects at saturation. The 72-h EC50, 72-h EC20, and 72-h EC10 (based on growth rate) were each reported as > 100% v/v saturated solution; the corresponding 72-h EL50, 72-h EL20 and 72-h EL10 (based on growth rate) were each reported as > 10 mg/L (based on the nominal loading rate).

Description of key information

ErL50 (72 h) > 10 mg/L (nominal loading rate)

ErL10 (72 h) > 10 mg/L (nominal loading rate)

Additional information

The toxicity of the substance to aquatic algae was tested in a guideline study following OECD Guideline 201. The test was set up as a limit test with a nominal test substance concentration of 10 mg/L (initial loading rate). The effects concentrations were based on the nominal test concentration of 100% v/v saturated solution which was prepared from an initial test solution with a nominal loading rate of 10 mg/L. The green algae Pseudokirchneriella subcapitata was exposed for 72 hours. An inhibition of algal growth was not observed. The reported ErL50(72 h) was >10 mg/L (nominal loading rate).   ErL10(72 h) was >10 mg/L (nominal loading rate).