2,6-dimethyloctan-2-ol

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

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

Justification for type of information:

Information is used for read across to Tetrahydromyrcenol

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

Key result

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: Measured concentrations confirmed nominal concentrations

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

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Measured concentrations confirmed nominal concentrations

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

Remarks:

as accoring to OECD TG 201

Conclusions:

The ErC50 and NOEC for algae tested according to OECD TG 201, are 80 and 25 mg/l, respectively .

Executive summary:

Algae toxicity was assessed in an OECDTG 201 study. Desmodesmus subspicatus were 72 hours exposed to Dihydromyrcenol at nominal concentrations of 0, 6.25, 12.5, 25, 50 and 100 mg/l . Analysis of the test concentrations showed that the nominal concentrations were in line with the measured concentration (> 80% of the nominal concentrations). At concentrations below 100 mg/l cells were intact, at 100 mg/l were few intact cells observed. The ErC50 and NOEC values were 80 and 25 mg/l, respectively. 

 

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                  

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Information is derived from analogue

Justification for type of information:

The read across justification is presented in the Toxicity to aquatic algae and cyanobacteria Endpoint summary. The file is also attached there.

Reason / purpose for cross-reference:

read-across source

Key result

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

Key result

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.

Conclusions:

For tetrahydromyrcenol the 72 h ErC50 and NOEC value for algae is 80 mg/L and 25 mg/L respectively, based on the read-across substance dihydromyrcenol.
The effect of the test item on the growth of Desmodesmus subspicatus has been investigated.

Executive summary:

For tetrahydromyrcenol, the 72 h ErC50 and NOEC value for algae have been derived from the read across substance dihydromyrcenol and were concluded at 80 mg/L and 25 mg/L respectively. In a 72 -hour acute toxicity study, cultures of Desmodesmus subspicatus were exposed to dihydromyrcenol at nominal concentrations, confirmed by analysis, of 0, 6.25, 12.5, 25, 50 and 100 mg/l in accordance with OECD guideline 201.  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 few intact cells were observed. The NOEC, ErC50 and EbC50 values were 25, 80 and 65 mg/l, respectively.

Description of key information

Tetrahydromyrcenol algae toxicity derived from Dihydromyrcenol using read across: ErC50 and NOEC are 80 and 25 mg/l, respectively.

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 algae toxicity of Tetrahydromyrcenol is derived from Dihydromyrcenol. First the experimental study of Dihydromyrcenol is presented and thereafter the read across justification. The accompanying file is also attached here.

Algae toxicity of Dihydromyrcenol

Algae toxicity was assessed in an OECDTG 201 study. Desmodesmus subspicatus were 72 hours exposed to Dihydromyrcenol at nominal concentrations of 0, 6.25, 12.5, 25, 50 and 100 mg/l . Analysis of the test concentrations showed that the nominal concentrations were in line with the measured concentration (> 80% of the nominal concentrations). At concentrations below 100 mg/l cells were intact, at 100 mg/l were few intact cells observed. The ErC50 and NOEC values were 80 and 25 mg/l, respectively. 

Tetrahydromyrcenol (18479-57-7) and its algae toxicity using read across information from Dihydromyrcenol (18479-58-78)

Introduction and hypothesis for the analogue approach

Tetrahydromyrcenol is a branched C8 alkyl chain to which a tertiary alcohol is attached at the end of the alkyl chain.For Tetrahydromyrcenol no algae experimental are available. In accordance with Article 13 of REACH,lacking information can be generated by means of applying alternative methods such asin vitrotests, QSARs, grouping and read-across. For assessing the algae toxicity of Tetrahydromyrcenol the analogue approach is selected because for one closely related analogue, Dihydromyrcenol, reliable algae toxicity data are available.

Hypothesis: Tetrahydromyrcenol has the same algae toxicity as Dihydromyrcenol.

Available experimental information: For Tetrahydromyrcenol Daphnia and Fish toxicity data are available but not for algae.For the analogue Dihydromyrcenol an OECDTG201 guideline algae study is available rated reliability Klimisch 1, providing a 72h-ErC50 of 80 mg/L and 72h-NOEC of 25 mg/L.

Target chemical and source chemical(s)

Chemical structures of the Tetrahydromyrcenol (the target) and are shown in the Data matrix including physico-chemical properties and toxicological information, thought relevant for aquatic toxicity.

Purity / Impurities

The purity and impurities of the target chemical do not indicate skin sensitisation potential other than indicated by the parent substance. The impurities are all below 10%.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation.

Structural similarities and differences:The target and the source chemicals both have a (2,6-dimethyl)octan-2-ol backbone, with a tertiary alcohol functional group. The difference is that Dihydromyrcenol has a double (unsaturated) bond at the end of the alkyl chain while Tetrahydromyrcenol has a saturated bond at the same site.

Bioavailability: Tetrahydro and Dihydro-myrcenolhave similar bioavailability based on similar molecular weight, both are liquids and both have similar physico-chemical properties (see data matrix).

Mode of Action and the algae toxicity:Tetrahydromyrcenol and Dihydromyrcenol) are both neutral organics and their ecotoxicity is driven by Log Kow; a substance with a higher Log Kow will be more toxic. Both substances have a similar log Kow and therefore their algae toxicity will be the same)

Other experimental information to support the read across:For both substances Daphnia toxicity is available, which indicate similar toxicity: 43.7 and 38 mg/l, respectively. 

Uncertainty of the prediction: In view of the reasoning above there are no additional uncertainties. 

Data matrix

The relevant information on physico-chemical properties and toxicological characteristics for the target and source substances are presented in the data matrix below.

Conclusions per endpoint for hazard and risk assessment

For Tetrahydromyrcenol the algae toxicity from Dihydromyrcenol can be used for which an algae test according to OECD TG 201 is available. This test resulted in an ErC50 of 80 mg/L and NOEC of 25 mg/L. A correction based on molecular weight is not considered necessary because the difference in molecular weight and log Kow are minimal.

Final conclusion on hazard: For Tetrahydromyrcenol the 72h-ErC50 and NOEC for algae are 80 and 25 mg/l, respectively. This value will be forwarded for the hazard and risk assessment.

Data matrix: Information on Tetrahydromyrcenol and Dihydromyrcenol to support the read across.

Common names	Target	Source
Chemical structures
Cas no of the main isomer	18479-57-7	18479-58-8
REACH registration	2018	2010
Einecs	242-361-9	242-362-4
Molecular weight	158.29	156.27
Physico-chemical data
Physical state	liquid	liquid
Melting point °C	< -20	<-20 (ECHA dissemination site)
Boiling point °C	201.9	193 (ECHA dissemination site)
Vapour pressure Pa (measured)	9.3	20 (ECHA dissemination site)
Water solubility mg/l (measured)	281.9	939 (ECHA dissemination site)
Log Kow (measured)	3.2	3.25(ECHA dissemination site)
Log Kow (calculated-EPIWIN)	3.6	3.5
Acute Aquatic toxicity
Fish mg/l	4.73 Ecosar prediction	27.8 (ECHA dissemination site, read across linalool)
Daphnia mg/l	43.7	38
Algae mg/l (ErC50)	Read across from Dihydromyrcenol	80
Long-term Aquatic toxicity
Algae mg/l (NOEC)	Read across from Dihydromyrcenol	25