2,6-dimethyloct-7-en-2-ol

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

At 0 and 72 hours, samples were taken from the control (replicates R1-R6 pooled) and each test group (replicates R1-R3 pooled) for quantitative analysis.

Due to the possible volatile nature of the test material, additional control and test preparations were made, these were incubated and remained unopened during the test. Samples from of these control and test preparations were taken for chemical analysis at 72 hours.

Vehicle:

no

Details on test solutions:

For the range-finding study, 100 mg of test material was dissolved into culture medium and adjusted to a 1 litre volume to give a 100mg/l stock solution. Further dilutions were made from this stock solution to generate test concentrations of 0.10, 1.0 and 10 mg/l.

For the definitive test, 500 mg of test material was dissolved directly into the culture medium and adjusted to a 5 litre volume to give a 100 mg/l stock solution. Dilutions were made from this stock solution to generate test concentrations to generate test concentrations of 6.25, 12.5, 25, 50 and 100 mg/l.

Control solutions were also prepared and did not contain any test substance.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Desmodesmus subspicatus
- Strain: CCAP 276/20
- Source (laboratory, culture collection): Culture Collection of Algae and Protozoa (CCAP), Dunstaffnage Marine Laboratory, Oban, Argyll, Scotland

Master cultures of Desmodesmus subspicatus were kept in the laboratory under constant aeration and illumination at 21 +/- 1 degrees C and maintained by replenishment of culture medium.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

24 +/- 1 degrees C

pH:

At 0 hours: 7.3 - 7.5
At 72 hours: 7.6 - 9.6

Nominal and measured concentrations:

Nominal concentrations for definitive study: 0 (control), 6.25, 12.5, 25, 50 and 100 mg/l (measured test concentration were 91% to 102% of nominal concentrations).

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 ml glass conical flasks
- Type (delete if not applicable): Flasks were plugged with polyurethane foam bungs
- Material, size, headspace, fill volume: Flasks were completely filled with no headspace, to restrict possible volatilisation loss
- Initial cells density: 4000 cells/ml
- Control end cells density: 4000 cells/ml
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes (additional sodium bicarbonate (500mg/l) was added to culture medium and the pH was adjusted to 7.0 +/- 0.1 with 0.1 N NaOH or HCl).

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Reverse osmosis purified deionised water (Elga Optima 15+ or Elga Purelab Option R-15 BP)

OTHER TEST CONDITIONS
- Adjustment of pH: yes (adjusted to 7.5 +/- 0.1 with 0.1N NaOH or HCl)
- Photoperiod: Continuous
- Light intensity and quality: approximately 7000 lux

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: Coulter Multisizer Particle Counter

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 0 (control), 0.10, 1.0, 10 and 100 mg/l
- Results used to determine the conditions for the definitive study: yes (0 (control), 6.25, 12.5, 25, 50 and 100 mg/l)

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

80 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: CL not calculable

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

65 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 95% CL: 56 - 65 mg/l

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

50 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Details on results:

Analysis of the test preparations showed that measured test concentration ranged from 91% to 102% of nominal indicating that no losses due to volatility occurred. As measured concentration confirmed nominal values, the latter were used for EC50 calculation.

The additional test replicates that were prepared and incubated alongside the test and remained unopened throughout the duration of the test showed test concentrations of 94-98% of nominal concentrations.

Observations on cultures: After 72 hours, no abnormalities were observed in the control or test cultures at test material concentrations of 6.25, 12.5, 25 and 50 mg/l. At 100 mg/l, few intact cells were observed.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this study the ErC50 is 80 mg/l, EbC50 is 65 mg/l and the NOEC is 25 mg/l.

Executive summary:

In a 72 -hour acute toxicity study, the cultures of Desmosdesmus subspicatus were exposed to the test item at nominal concentrations, confirmed by analysis, of 0, 6.25, 12.5, 25, 50 and 100 mg/l in accordance with OECD guideline 201.  The NOEC, ErC50 and EbC50 values were 25, 80 and 65 mg/l, respectively. 

 

At 72 hours, no abnormalities of cultures with test material concentrations of 6.25, 12.5, 25, and 50 mg/l test were observed. At 100 mg/l were few intact cells observed.

 

This toxicity study is classified as acceptable and satisfies the guideline requirements for the acute toxicity to algae study.

 

Results Synopsis

 

Test Organism: Desmodesmus subspicatus

Test Type: static

 

72-hr ErC50: 80 mg/l                     

72 -hr EbC₅₀: 65 mg/l                95% C.I.:  56 to 65 mg/l

72 -hr NOEC: 25 mg/l                  

Description of key information

One key study has been identified as adequate to assess the toxicity of the test item to aquatic algae. This study followed the OECD 201 guideline and was GLP-compliant.

Key value for chemical safety assessment

EC50 for freshwater algae:

80 mg/L

EC10 or NOEC for freshwater algae:

25 mg/L

Additional information

The test item gave 72h ErC50 and EbC50 values of 80 and 65 mg/l respectively in the key algal growth inhibition study.