Benzyltoluene

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From the 15th March to the 22th April 1996

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

yes

Remarks:

Other observed potential effects than immobilisation were not indicated

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 3 samples are taken in solutions at the concentration tested just prior assay and at the end of the 48-h exposure period
- Sampling method: 1-mL sample

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Test substance Jarylec C100 with a specific activity of 0.055 Ci/mg is diluted in isopropanol at 0.5 mCi/mL.
Saturated solution is prepared by vigorous shaking of 360 µg of JARYLEC C100 (40 µL of solution of JARYLEC C100 in isopropanol) in 1L of test medium for 64 hours. Then, solution is decanted and distributed in testing containers. These containers are maintained in the dark for 2 days for checking that saturation equilibrium is reached.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Isopropanol
- Concentration of vehicle in test medium (stock solution and final test solution): 40 µL/L
- A blank containing 40µg/L of isopropanol is run in parallel to check toxicity of vehicle

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnid
- Strain: Clone 5 or clone A
- Source: Testing laboratory
- Feeding during cultivation: Elendt M7 + algae (Raphidocelis subcapitata).
- Age at study initiation (mean and range, SD): younger than 24 hours

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Post exposure observation period:

none

Hardness:

The addition of Ca and Mg ions equals 2.5 mmol/L: Ca/Mg = 4

Test temperature:

19-21°C, room thermostated.

pH:

pH initial was measured to be 7.67 at test begining in the highest test concentration. At the end of the 48-h exposure period, it was measured to be 7.42, 7.58 and 7.74 in test solution, control vehicle solution and control blank solution, respectively.

Dissolved oxygen:

At the end of the 48-h exposure period, the dissolved oxygen was measured to be 7.0, 7.8 and 8.3 mg/L in test solution, control vehicle solution and control blank solution, respectively.

Salinity:

the test medium composition is the one describes in ISO 6341 standard.

Nominal and measured concentrations:

The nominal concentration corresponded to the saturated concentration of the solution.
Ratio between measured initial (0.236 mg/L) and final (0.237 mg/L) concentrations was 100%.

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type : closed
- Material, size, headspace, fill volume: penicillin type 120 ml, closed with sealed PTFE septa, fill volume : 120 mL (no headspace)
- Aeration: no
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): 4


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: ultra-pure water
- Ca/mg ratio: 4
Components:
11.76 g CaCl2, 2H2O/L
4.93 g Mg SO4, 7H2O/L
2.59 g ofNaHCO3/L
0.23 g of KCl/L

- Light intensity: protected from light

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
mobility

TEST CONCENTRATIONS
Saturated solution (measured value = 0.236 - 0.237 mg/L)
- Justification for using less concentrations than requested by guideline: poor solubility: limit test at WSL

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

> 0.24 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: measured final= measured initial

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.24 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: measured final= measured initial

Duration:

48 h

Dose descriptor:

EC0

Effect conc.:

0.24 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: measured final= measured initial

Details on results:

No immobilisation of daphnids was observed at any sampling time and in any test group.
Measured test substance concentration was 0.236 mg/L at T0 and 0.237 at T=48h

Results with reference substance (positive control):

EC50 obtained for potassium dichromate at 24 h was 0.83 mg/L

Validity criteria fulfilled:

yes

Remarks:

Immobilisation in control groups was 0%; dissolved oxygen and measured pH were in the recommended ranges; mesured final concentration was above 80% of the initial concentration

Conclusions:

No immobilisation of daphnia was observed for exposure during 48 h at solubility limit in test medium. Therefore EC50 of Jarylec C100 at 48 h for Daphnia magna was determined to be > 0.24 mg/L, found to correspond to the solubility limit of the tested substance in the mineral medium used for this test. Consequently benzyltoluene itself at solubility limit does no induces acute toxicity on daphnia.

Executive summary:

The acute toxicity (inhibition of mobility) of JARYLEC C100 (benzyl/dibenzyltoluene) for Daphnia magna was assessed according to the method C2 of the European Directive 92/69/CEE. Daphnia were exposed in a static test to a concentration of about 0,24 mg/l. The test was performed with 5 daphnia per vessel. The test was performed using closed flasks entirely filled with test solutions and closed with butyl rubber caps covered with PTFE. The test concentrations of JARYLEC C100 were measured by Liquid scintillation counting.

No inhibition of mobility was observed after 24 or 48 hours at a tested concentration of about 0,24 mg/L of JARYLEC C100. This concentration is the solubility limit of JARYLEC C100 in the mineral medium used for the test; it is about 4 times above its solubility limit in pure water.

The method was applied with respect to its quality criteria :

Immobilisation in the control did not exceed 10 % at the end of the test ;

Concentration of dissolved oxygen in the test vessels remained above 2 mg/L at the end of the test and pH did not vary by more than 1 unit ;

The concentrations of the test substance have been maintained to within 80 % of the initial concentration throughout the duration of the test.

Description of key information

Benzyltoluene is not acutely toxic to daphnia at water solubility limit observed in the test media. No immobilisation of daphnia was observed for exposure during 48 h at solubility limit in test medium. Therefore EC50 of Jarylec C100 at 48 h for Daphnia magna was determined to be > 0.24 mg/L, found to correspond to the solubility limit of the tested substance in the mineral medium used for this test.