3,7-dimethylocta-1,3,6-triene

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

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 202 (Daphnia sp. Acute Immobilisation Test)

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

2008

Qualifier:

according to guideline

Guideline:

ISO 6341 (Water quality - Determination of the Inhibition of the Mobility of Daphnia magna Straus (Cladocera, Crustacea))

Version / remarks:

2012

Qualifier:

according to guideline

Guideline:

other: OECD Series on testing and assessment, No. 23, "Guidance document on aquatic toxicity testing of difficult substances and mixtures"

Version / remarks:

December, 2000

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Single samples for analysis were taken from the control and all test concentrations from replicates without daphnids (except at the end of the test: replicates with daphnids) at the start of the test (t=0h), at t=24h (new and old solutions) and the end of the test (t=48h).

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
The standard test procedures required preparation of test solutions, which should contain completely dissolved test substance concentrations or stable and homogeneous mixtures. The stock and test solutions were prepared under closed conditions and gently stirred to avoid production of a dispersion.

Two stock solutions (one for the fresh medium at t=0h and another for the fresh medium at 24h) were prepared by slow-stirring. The mixing vessel was a cylindrical glass bottle sealed with screw cap and fitted with a drain port near the bottom for drawing off the saturated solution. The volume of the mixing vessel was approximately 1 L. A magnetic stirring bar was placed in the vessel and 1L of test water was added. Then an excess ot the test item (1.1 g for the fresh medium at t=Oh and 1.4 g for the fresh medium at t=24h) was carefully added directly to the surface of the test water and the vessel was sealed immediately. The mixing was initiated with the vortex in the centre extending maximally around 10% vessel depth from the top to the bottom of the vessel. The stirring speed was kept as low as possible to maintain mixing of the water phase without dispersing the test substance in the water phase. After 24 ± 2 hours of gentle stirring with at least one-hour settling period, the saturated aqueous phase was taken out of the drain port. The first 100 mL were discarded and samples were taken from the following stock solution and chemically analysed. Then the stock solution was diluted with test water as necessary into 200-mL volumetric flasks (filled up to the meniscus) to obtain the required test concentrations based on the measured concentration of the stock solution (4.44 mg/L for the fresh medium at t=0h and 4.48 mg/L for the fresh medium at t=24h). Each prepared concentration was inverted several times before filling the test tube (without headspace) to ensure adequate mixing and homogeneity. After filling the vessels were sealed immediately with screwcaps after introduction of daphnids.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Clone: clone 5
- Sex: female
- Origin LIEBE - CNRS UMR 7146 - UFR SciFA - Université de Lorraine Campus Bridoux Bát. IBISE, 8, rue du Général Delestraint - 57070 METZ, bred in the Laboratoires des Pyrénées et des Landes.
- Validity of batch: Daphnids originated from a healthy stock, showing no signs of stress such as mortality, presence of males, ephippia or discoloured animals.
- Breeding conditions: Daphnids were cultured in the Laboratoires des Pyrénées et des Landes under similar temperature and light conditions as used in the test. Cultures were maintained at a density of 1 adult daphnid per 25 mL of culture medium. During the week the stock daphnids were fed daily with a suspension of freshwater algae (mix of 3 algae strains: Chlorella vulgaris = 2.5E+06 cells/mL/day/daphnid, Desmodesmus subspicatus = 2.5E+06 cells/mL/day/daphnid and Pseudokirchneriella subcapitata = 5E+06 cells/mL/day/daphnid). The water was changed once per week. These culture conditions maintained the daphnids in the parthenogenetic reproductive stage.

ACCLIMATION:
- At least 48 hours prior to the start of the test, gravid daphnids were transferred to OECD test water and held at similar temperature and light conditions as used in the test. During this period, daphnids were fed in the same manner as that of the stock population. Only daphnids up to 24 hours old were used for the test.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

approximately 250 mg/L (as CaCO3)

Test temperature:

19.9 - 20.7 °C

pH:

- Start: 7.85 - 7.90
- End: 7.73 - 7.83

Dissolved oxygen:

- Start: 8.67 - 8.82 mg/L
- End: 8.21 - 8.76 mg/L

Nominal and measured concentrations:

- Nominal concentrations: 0 (control), 1.0, 1.3, 1.7, 2.3, 3.0 and 4.0 mg/L (based on a range-finding study)
- Measured concentrations (geometric means): - (control), 0.655, 0.928, 1.161, 1.552, 1.968, 2.994 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessels: all-glass test tubes of approximately 20 mL capacity sealed with screwcaps. Each test vessel was uniquely identified with study code, replicate number, date of experimentation and concentration
- Number of daphnids: 20 per control and test concentration, divided into 4 groups of 5 animals
- Loading: 5 daphnids per vessel each completely filled with test solution and without headspace
- Number of replicates: 4 replicates with daphnids for the control and per test concentration prepared on the basis of the concentration measured in the stock solution. Moreover, 3 abiotic replicates for the control and per test concentration were prepared for analytical verification of test concentrations.
- Aeration: no, although test water was aerated prior to the test (see 'TEST MEDIUM / WATER PARAMETERS).
- Feeding during test: no
- Introduction of daphnids: daphnids were introduced into the test medium immediately after filling the test tubes with test solutions.
- Age at test start: < 24 hours old

TEST MEDIUM / WATER PARAMETERS:
- Test water: reconstituted water, as prescribed by the OECD Guideline 202
- Stock solutions: CaCl2·2H20: 11.76 g/L; MgSO4·7H2O: 4.93 g/L; NaHCO3: 2.59 g/L; KCl: 0.23 g/L
- Other: an aliquot (25 mL) of each solution was added to each litre (final volume) of deionised water (conductivity < 10 µS/cm). The pH of this solution was in the range of 6 to 9 and the total water hardness was approximately 250 mg/L (as CaCO3). This reconstituted water was aerated until the dissolved oxygen concentration was approximately air-saturation value, and then set aside for 2 days without aeration.

OTHER TEST CONDITIONS
- Light regime: 16h light : 8h dark

EFFECT PARAMETERS MEASURED
- Immobility: immobility and abnormal behaviour were determined by visual observation after 24 and 48 hours. Immobile animals were eliminated from the vessels as soon as they were discovered. The daphnids were considered to be immobile if they were not able to swim within 15 seconds after gentle agitation of the test vessels.
- pH and dissolved O2: At the start of the test (t=0h), at t=24h (new and old solutions) and the end of the test (t=48h) in all vessels.
- Temperature of medium: measured continuously in a vessel next to the test vessels, over the entire study period, beginning at the start of the test.

RANGE-FINDING STUDY
- Test concentrations: 0.1, 1.0 and 2.0 mg/L and a concentration close to the water solubility limit
- Results used to determine the conditions for the definitive study: after 48 hours of exposure, immobilisations were 0% at 0.1 and 1.0 mg/L, 70%^at 2.0 mg/L and 100% at the maximum of solubility

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.47 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% C.L.: 1.366 - 1.578 mg/L

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

1.792 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% C.L.: 1.678 - 1.931 mg/L

Details on results:

See 'Any other information on results incl. tables'. After 48 hours of exposure, immobilisation was observed from the measured concentration (geometric mean) of 1.161 mg/L and increased in a dose-dependent manner.

Results with reference substance (positive control):

The most recent test performed on July 24 (2013), determined a 24h-EC50 of 0.98 mg/L

Reported statistics and error estimates:

The evaluation of the effects was based on the measured test item concentrations. The software ToxRat® Professional was used for the determination of the effective concentrations.

Table: immobility of daphnids after 24 and 48 hours exposure

Nominal concentration (mg/L)	Measured concentration (mg/L)	Number of daphnids exposed	Response at 24h		Response at 48h
			Number	Total (%)	Number	Total (%)
Control	Control	20	0	0	0	0
1.0	0.655	20	0	0	0	0
1.3	0.928	20	0	0	0	0
1.7	1.161	20	0	0	2	10
2.3	1.552	20	3	15	11	55
3	1.968	20	15	75	20	100
4	2.994	20	20	100	20	100

Validity criteria fulfilled:

yes

Conclusions:

The 48-h EC50 value is 1.47 mg/L in Daphnia magna.

Executive summary:

The acute toxicity to aquatic invertebrates was determined in a study according to OECD TG 202 and in compliance with GLP criteria. In this study daphnids (D. magna, 20 per concentration) were exposed to nominal concentrations of 0 (control), 1.0, 1.3, 1.7, 2.3, 3.0 and 4.0 mg/L which were based on a range-finding study for 48 hours under semi-static conditions. Immobility and abnormal behaviour were determined after 24 and 48 hours exposure. Analytical confirmation of nominal test concentrations showed that the deviation of the exposure concentrations of the test substance was greater than ± 20% of the nominal concentrations (according to the measured concentrations of the second day), and therefore the results are expressed in terms of geometric means of the exposure concentration. The average exposure concentrations (geometric means) were calculated to correspond to: 0.655, 0.928, 1.161, 1.552, 1.968 and 2.994 mg/L. After 48 hours of exposure, immobilisations were 0% at 0.655 and 0.928 mg/L, 10% at 1.161 mg/L, 55% at 1.552 mg/L and 100% at 1.968 and 2.994 mg/L. Based on these data, the 48-h EC50 value is determined at 1.47 mg/L (95% C.L. 1.366 - 1.578 mg/L).

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

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: read-across from a guideline study

Justification for type of information:

The acute Daphnia toxicity of Ocimene is based on read-across from Myrcene. The documentation is presented in the Endpoint summary of Aquatic toxicity.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.47 mg/L

Basis for effect:

mobility

Description of key information

No data is available for the substance itself. Therefore read-across is performed to the close structural analogue Myrcene (CAS# 123-35-3). The experimental study of Myrcene is presented below. The read across justification is presented in the Aquatic endpoint summary.

Myrcene acute Daphnia toxicity

Its acute toxicity to aquatic invertebrates was determined in a study according to OECD TG 202 and in compliance with GLP criteria. In this study daphnids (D. magna, 20 per concentration) were exposed to nominal concentrations of 0 (control), 1.0, 1.3, 1.7, 2.3, 3.0 and 4.0 mg/L, which were based on a range-finding study, for 48 hours under semi-static conditions. Immobility and abnormal behaviour were determined after 24 and 48 hours exposure. Analytical confirmation of nominal test concentrations showed that the deviation of the exposure concentrations of the test substance was greater than ± 20% of the nominal concentrations (according to the measured concentrations of the second day), and therefore the results are expressed in terms of geometric means of the exposure concentration. The average exposure concentrations (geometric means) were calculated to correspond to: 0.655, 0.928, 1.161, 1.552, 1.968 and 2.994 mg/L. After 48 hours of exposure, immobilisations were 0% at 0.655 and 0.928 mg/L, 10% at 1.161 mg/L, 55% at 1.552 mg/L and 100% at 1.968 and 2.994 mg/L. Based on these data, the 48-h EC50 value is determined at 1.47 mg/L (95% C.L. 1.366 - 1.578 mg/L). There is no need to convert the Myrcene toxicity data towards Ocimene, because of the similarities in molecular weight and log Kows.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1.47 mg/L