Isobutylbenzene

Short-term toxicity to aquatic invertebrates

Administrative data

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

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

yes

Remarks:

Teh deviations had no impact on the study results.

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Isobutylbenzene

EC Number:

208-706-2

EC Name:

Isobutylbenzene

Cas Number:

538-93-2

Molecular formula:

C10H14

IUPAC Name:

(2-methylpropyl)benzene

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Test solutions were collected from each control and test loading rate at test initiation, test solution renewal, and at test completion. At test initiation and start of the renewal, sub-samples of the test solutions were collected from the vessels used to prepare the test solutions (bulk). At test completion and end of the renewal, sub-samples of test solution were pooled from each of the four replicates to create one sample per loading rate. Approximately 40 mL of the each control and test loading rate were collected in amber glass containers of appropriate size and stored refrigerated (2°C to 8°C) until analysis. An aliquot of control media (dilution water) was also collected at test initiation. Sub-sample containers were filled as much as possible to reduce headspace.

Test solutions

Vehicle:

no

Details on test solutions:

The test item is a mono-constituent organic liquid; with a water solubility of 12 mg/L ± 1 mg/L at T = 20.0°C ± 0.5 °C. The test solutions were prepared as water accommodated fractions (WAFs) using the methodology described below. The test item was also found to be volatile in aqueous solutions; therefore, extra effort was taken to reduce headspace and exposure to the laboratory environment as per the OECD 23 Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (OECD 2000).
Water accommodated fractions (WAFs) were prepared at 3.125, 6.25, 12.5, 25, 50, and 100 mg/L nominal loading rates (Table 6-3) and tested alongside a negative control and a WAF (method) control.
To prepare the WAFs, the test item was weighed and added directly to approximately 2.5L of dilution water in a 5L glass aspirator bottle. The solutions were then brought up to the 5L mark using dilution water. A WAF control (0 mg/L) was prepared alongside the test item WAFs; however, no test item was added, and a total of 5L was prepared. Immediately following preparation, WAFs were sealed with Parafilm®.
Each WAF solution was stirred using a magnetic stir bar and stirrer using a slow stir method. Stirring occurred for approximately 40 hours at which time the solution were allowed to settle undisturbed for approximately 1.5 hours.
WAF solutions were removed from the mixing vessel and collected in a glass holding vessel (1000mL glass beaker) by draining from the bottom third of the aspirator bottle, discarding the first ~100 mL, into an appropriate container and was immediately covered with Parafilm®. WAF solutions were drained from low loading rate to high loading rate to prevent cross contamination. The test item was found to be volatile in aqueous solutions; therefore, extra effort was taken to reduce headspace and exposure to the laboratory environment.
The test item was handled according to the Work Instruction for the Management of Test and Reference Items for GxP Studies (BBY1 WI-00008). All chemicals were weighed using analytical balances, which were operated according to the procedures outlined in the Corporate Procedure for Balance Calibrations and Verifications (COR WI-00015). All containers and apparatus used were new or thoroughly cleaned according to the Work Instruction for Cleaning of Laboratory Ware (BBY WI-00001).

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Strain/clone: not specifed
- Source: In-house culture; original culture was obtained from Aquatic BioSystems (Fort Collins, CO) in 2017 (identified by EcoAnalysts Inc. on March 10, 2016 as D. magna)
- Age of parental stock (mean and range, SD): not indicated
- Feeding during test: no
- Age of animals used in the study: < 24 h

ACCLIMATION
- Acclimation period: not required
- Acclimation conditions (same as test or not): yes
- Type and amount of food: approximately 4.0 mL of Pseudokirchneriella subcapitata (PKS) and 1.0 mL yeast-cereal-grass fermented-trout-chow (YCT)
- Feeding frequency: 3-times per week
- Health during acclimation (any mortality observed): 9.4 % mortality

Study design

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test conditions

Hardness:

100 mg/L CACo3

Test temperature:

19.5 - 20.7 °C

pH:

8.1 - 8.2

Dissolved oxygen:

8.6 - 9.1 mg/L

Nominal and measured concentrations:

Nominal: 0, 3.215, 6.25, 12.5, 25, 50, 100 mg/L
mean mesured: < 0.05; < 0.05, 0.49, 0.55, 0.64, 0.88, not applicable, 1.14 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: ~125 mL glass jar covered with Teflon lined lid
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: ~125 ml
- Aeration: no
- Renewal rate of test solution (frequency/flow rate): daily
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per WAF (method) control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to OECD 202
- Culture medium different from test medium: no
- Intervals of water quality measurement: daily

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16:8 h day night regime, with 30 min transition peroid
- Light intensity: 528 – 566 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : immobility after 24 and 48 h

VEHICLE CONTROL PERFORMED: n.a.

Reference substance (positive control):

yes

Remarks:

Zink sulphate heptahydrate

Results and discussion

Effect concentrations

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.6 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Results with reference substance (positive control):

48 h EC50: 0.78 mg/L

Reported statistics and error estimates:

The 48 hour ELR50 along with the 95% confidence limits (based on both nominal loading rates and mean measured test item concentrations) and the NOELR and LOELR values for immobilisation were determined using a computerised statistical package, CETIS™ (Version 1.9.2.4),.