Hydrocarbons, C7-C9, isoalkanes

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species, other

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: Acceptable, well documented publication which meets basic scientific principles

Justification for type of information:

A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across: supporting information

Principles of method if other than guideline:

Bioconcentration factors (BCFs) were calculated by comparing the toxicant concentrations in tissue with aqueous concentrations at the end of the exposure period, the point in the experiment where the concentrations in tissue and water were considered by the authors to be nearest to equilibrium.

GLP compliance:

not specified

Radiolabelling:

not specified

Details on sampling:

Samples of test solution/feeding algae cell suspension was taken 5 times at intervals of 20 min, giving a total measurement period of 80 min.

Vehicle:

yes

Details on preparation of test solutions, spiked fish food or sediment:

For clearance rate measurements 2 x 20 L of toxicant in filtered seawater (FSW) and 2 x 20 L of 'control' FSW containing 0.005 % v/v acetone were prepared. Glass aspirators of 20 L capacity were filled with 20 L of FSW at 15°C and the contents stirred with a magnetic system (35-mm Teflon coated follower) until a vortex was produced. Aliquots (1 mL) of acetone (Fisons, HPLC grade) solutions of toxicant were added by means of a glass-tipped autopipette discharged just below the liquid surface in the vortex. Any emulsion formed was held in the vortex until the material dissolved. Acetone (1 mL) was added to 'control' aspirators in the same way. The aspirators were stoppered and contents stirred in the dark for a minimum of 2 h before use.

- Chemical name of vehicle (organic solvent, emulsifier or dispersant): acetone

Test organisms (species):

other: Mytilus edulis

Details on test organisms:

TEST ORGANISM
- Common name: Blue mussel
- Source: were collected from the intertidal zone of Beggar's Island at the confluence of the Lynher and Tamar Rivers, which is near Plymouth, England
- Length at study initiation (lenght definition, mean, range and SD): 40 - 50 mm
- Description of housing/holding area: Organisms were cleaned of epibionts and held in open-flow tanks that recirculated seawater (1000 L) with 33% salinity and a tidal cycle that exposed the organisms to the air for 2.5 hours, two times in a 24-hour period. Temperature was initially at field-ambient, which increased 2ºC per day until reaching 15ºC.
- Feeding during test
- Food type: diatom Phaeodactylum tricornutum
- Amount: P. tricornutum culture was added to achieve a concentration of 28 to 36 E3 cells/ml.
- Frequency: alga are provided once


ACCLIMATION
- Acclimation period: The organisms were further acclimated for 7 days.
- Feeding frequency, type and amount of food: fed with the diatom Phaeodactylum tricornutum during the entire acclimation phase at at rate of approximately 8 mg dry algal mass / animal / day.

Route of exposure:

aqueous

Test type:

static

Water / sediment media type:

natural water: marine

Total exposure / uptake duration:

105 min

Test temperature:

15°C

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type: covered with Perspex lids that contained a small hole to allow for the addition of alga cells and minimize the loss of more volatile test substances
- Material, size, headspace, fill volume: 2 L beaker containing 2 L of seawater
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 14
- No. of vessels per control: 1

Nominal and measured concentrations:

A minimum of 4 treatment concentrations up to the water solubility limit in seawater was evaluated.

Reference substance (positive control):

not specified

Details on estimation of bioconcentration:

Bioconcentration factors (BCF) were calculated by comparing the toxicant concentration in the tissues with its concentration in the water at the end of the exposure period, the point in the experiment where the concentrations in tissue and water were nearest to equilibrium. This approach to equilibrium calculation more closely reflects the steady-state conditions which would be achieved by continuous exposure and corrects for the greater proportional removal of the more hydrophobic (highly bioaccumulated) compounds from the water in our static system. Water concentrations at the end of the exposure were estimated retrospectively by substracting the quantity of compound taken up in the mussel tissue from the amount measured in the water at the start of exposure. This procedure is based on the assumption that there were no significant losses due to volatilisation or absorption on glassware during the 105-min exposure period. This assumption was verified experimentally for several other compounds studied. Aqueous exposure concentrations have also been expressed as the estimated concentrations in the water at the end of the experiments.

Key result

Type:

BCF

Value:

198.7 dimensionless

Basis:

whole body w.w.

Remarks:

The study was not designed to determine the time at which tissue concentrations reached a plateau/steady state. The reported BCF was measured after a 105 minute exposure.

Remarks on result:

other: Conc.in environment / dose:not specified

Type:

other: EC50 (=WEL50) in mg/L

Value:

0.12 other: mg/l

Basis:

other: loading level of test substance in water that reduced by 50% the uptake rate of algae by mussels in comparison to the pre-exposed control rate over a 105 minute exposure.

Remarks on result:

other: 95% CL: 0.10-0.13

Remarks:

Conc.in environment / dose:not specified

Type:

other: TEC50 (TissueEC50) in mg/kg

Value:

24.6 other: mg/kg

Basis:

other: concentration of test substance in tissue that reduced by 50% the uptake rate of algae by mussels in comparison to the pre-exposed control rate over a 105 minute exposure.

Remarks on result:

other: 95% CL: 22.7-26.6

Remarks:

Conc.in environment / dose:not specified

Log BCF = 2.3

No information on exposure solution parameters was reported and aqueous exposure solutions were not analytically verified.

Validity criteria fulfilled:

not applicable

Conclusions:

Under the conditions of this study, a BCF of 198.7 was measured with the mussel, Mytilus edulis, after a 105 minute exposure to the test substance. Based on the maximum uptake rate of algae by mussels over a 105 minute exposure period, the test solution aqueous EL50 was 0.12 mg/L and the tissue EC50 was 24.6 mg/kg (wet weight).

Executive summary:

Under the conditions of this study, a BCF of 198.7 was measured with the mussel, Mytilus edulis, after a 105 minute exposure to the test substance. Based on the maximum uptake rate of algae by mussels over a 105 minute exposure period, the test solution aqueous EL50 was 0.12 mg/L and the tissue EC50 was 24.6 mg/kg (wet weight).

Description of key information

There is no data available for this substance. However, key data is available for the structural analogue Octane and is presented in the dossier. The data is read across to this substance based on analogue read across and a discussion and report on the read across strategy is provided as an attachment inIUCLID Section 13.

Under the conditions of this study, a BCF of 198.7 was measured with the mussel, Mytilus edulis, after a 105 minute exposure to the test substance. Based on the maximum uptake rate of algae by mussels over a 105 minute exposure period, the test solution aqueous EL50 was 0.12 mg/L and the tissue EC50 was 24.6 mg/kg (wet weight).

Additional information

For the purpose of PBT assessment (Annex XIII), a combination of QSAR models and experimental data for both screening and assessment level information are utilized, in accordance with REACh Annex XI and ECHA Guidance on integrated testing and evaluation strategies (R.11). As a result, single values or ranges of values reported for individual endpoints within the substance registration should be considered within this weight of evidence context and not applied individually for the purpose of PBT assessments. A complete, integrated PBT assessment for the range of relevant constituents within petroleum hydrocarbon UVCB substances is attached to this dossier (section 13.2).