Oct-2-ene

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

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other: GLP compliant, guideline study, available as unpublished report, acceptable with restrictions

Justification for type of information:

Read-across between the target substance Oct-2-ene (EC 203-894-2 / CAS 111-67-1) and source substance 1-Decene (EC 212-819-2/ CAS 872-05-9) is based upon the similarity of the chemical structures and their respective physico-chemical properties. The ECHA Read-Across Assessment Framework (RAAF) states that substances with qualitatively similar properties can form the basis of read-across in circumstances where the source and target substances share such similar characteristics.
Target substance Oct-2-ene and source substance 1-Decene are each mono-constituent linear olefins. Structurally, the differences between source and target substances include: 1) the length of the carbon chain (eight for the target substance, and ten for the source substance); and 2) the location of the carbon-carbon double bond (uniformly at the C2 position for the target substance, but uniformly at the C1 terminal position for the source substance).
The target and source substances both fit within the boundaries of chemical category of higher olefins. Studies conducted by the HOPA consortium on a large range of higher olefin category members (including 1-Decene) demonstrated sufficiently similar physico-chemical, environmental fate and toxicological properties to substantiate the basis for read-across; category members in the C6-C10 range may be moderately toxic to highly toxic to aquatic organisms and environmental toxicity is expected to be manifested as non-polar narcosis. Therefore Oct-2-ene (which falls within the C6-C10 range) is expected to behave similarly. Justification for inclusion of Oct-2-ene within the boundaries of the higher olefins category, and the relevance of each category member as an analogue substance to Oct-2-ene, is provided in Section 13 (Document name: “HOPA Higher Olefins CJD with Category Matrix Report [rev 1 Sept 2016]”; Document name: "ACC Product Stewardship Summary for Higher Olefins Category (2008-12-03)”).

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples taken at 0 and 72 hours in exposure vessels and controls.

Vehicle:

yes

Details on test solutions:

A concentrated 10 mg/ml stock solution of dodec-1-ene was made by adding 100mg in 10 ml DMF.

The required amount of the stock solution was then added to dechlorinated water and stirred for 48 hours in airtight sealed vessels with the minimum headspace to give the required exposure concentrations. DWC and solvent control test solutions were also be stirred for 48 hours.

Test organisms (species):

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

Details on test organisms:

Strain ATCC 22662. Stock cultures will be maintained under axenic conditions.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations of 0.056, 0.1, 0.18, 0.32, 0.56, 1 and 1.8 mg/l.
Mean measured concentrations of

Details on test conditions:

Glass bottles of 50 ml nominal capacity, filled completely (approximately 60 ml of test solution), with airtight, Teflon faced disc/crimp closures. Under continuous illumination of approximately 6000 lux, with orbital shaking at 160 ± 10 rpm.

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 - < 1.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Validity criteria fulfilled:

yes

Conclusions:

The 72 hour ErC50 is between 1-1.8 mg/l.

Executive summary:

The toxicity of dec-1 -ene to Pseudokirchneriella subcapitata was investigated in an OECD 201 test (Brixham Environmental Laboratories, 2010). Due to the low solubility of the test substance the study used a solvent carrier. The test substance was mixed with the solvent before being added to the dilution water. It was then stirred for 48 hours under sealed conditions to maximise the exposure concentrations. The test was carried out in sealed test vessels to minimise the loss of the test substance.

At the lower loading rates (0.056 -0.1mg/l) the measured concentrations were below the limit of detection throughout the test. Only the three highest exposure concentrations had detectable levels of dec-1 -ene after 72 hours. Due to the loss of test compound over time the results are reported based on nominal loading rates. The 72 hour ErC50 lies between 1 and 1.8mg/l and the analytical monitoring indicates that the mean exposure concentration at 1.8mg/l was below the limit of solubility of dec-1 -ene.

Description of key information

The key study was an algal growth inhibition test of an analog substance on the freshwater unicellular green alga, Pseudokirchneriella subcapitata following OECD Guideline 201 (Brixham Environmental Laboratories, 2010). The test substance caused a reduction of growth in the algal cultures (test units) exposed to nominal concentrations between 1 and 1.8 mg/L. Therefore, the72-h ErC50 (based on growth rate) was reported as > 1 and < 1.8 mg/L. The key value was represented by the minimum value from the reported range of the ErC50 values.

Key value for chemical safety assessment

EC50 for freshwater algae:

1 mg/L