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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
23 November 2009 - 13 August 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study conducted according to international guidelines
Justification for type of information:
see read across rationale in Section 13.2
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 1.0 mg/L

- Sampling method: At the start of the definitive test, four samples (5 mL) were taken from the freshly-prepared control and test media. After 48 hours, the contents of the test vessels from the control and test medium were pooled and further samples were taken for analysis. All samples were added to acetonitrile (5 mL) in order to minimise further degradation of the parent material.

- Sample storage conditions before analysis: On each occasion, two of the samples were analysed and the others were stored in a freezer in case further analysis was required.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
The method of preparation used during the definitive test was based on the results of an analytical trial and range finding tests. The test substance (10 mg) was dispersed in dilution medium (10 L) in an aspirator. The contents of the aspirator were stirred for approximately 16 hours; one litre of the resultant medium was then filtered (through a pre-conditioned 0.2 Hm nitrocellulose filter) to provide the test medium.

- Controls: diluted medium

- Chemical name of vehicle (organic solvent, emulsifier or dispersant): After discussions with the Sponsor, it was agreed that the use of solvent was not appropriate therefore an analytical trial was carried out to determine the rate of degradation of the parent material. After further discussions with the Sponsor, a second range finding test was performed, employing a nominal test concentration of 1.0 mg/L. After 48 hours, all of the Daphnia at 1.0 mg/L were mobile.

- Concentration of vehicle in test medium (stock solution and final test solution): no vehicle used

- Evidence of undissolved material (e.g. precipitate, surface film, etc): none reported
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Daphnia Magna
- Strain: Straus
- Source: Institute National de Recherche Chimique Appliqué (IRChA), France

ACCLIMATION

- Type and amount of food: suspension of the unicellular green algae, Pseudokirchneriella subcapitata, to provide nominally 0.1 to 0.2 mg carbon per daphnid, per day, except during the initial three days when a slightly lower ration was given.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Post exposure observation period:
Not applicable
Hardness:
250 mg/L as CaCO3
Test temperature:
Measured temperatures were between 21.2 and 21.9 °C
pH:
Measured pH were between 7.8 and 7.89
Dissolved oxygen:
Measured values (% air saturation value) were between 98 and 101
Salinity:
Not applicable to freshwater study
Nominal and measured concentrations:
Control nominal 0 mg/L; measured - non detected
Test: nominal 1 mg/L (loading rate); measured - 0.0219 mg/L (mean of 0.0212 and 0.0225 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: glass dishes
- Type (delete if not applicable): loosely covered
- Material, size, headspace, fill volume: test vessles contained 100ml of medium
- Renewal rate of test solution (frequency/flow rate): No
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The medium was prepared in deionised, reverse osmosis water.
- Culture medium different from test medium: No

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: 16 hours light : 8 hours dark
was maintained, with periods of subdued lighting at the beginning and end of each light phase.

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

TEST CONCENTRATIONS
- Spacing factor for test concentrations: none - limit test
- Justification for using less concentrations than requested by guideline:
- Range finding study:
The first range finding test employed nominal test concentrations of 0.1, 1, 10 and 100 mg/L and dimethylformamide was used to dissolve the test substance before its addition to aqueous media. After discussions with the Sponsor, it was agreed that the use of solvent was not appropriate therefore an analytical trial was carried out to determine the rate of degradation of the parent material. After further discussions with the Sponsor, a second range finding test was performed, employing a nominal test concentration of 1.0 mg/L. After 48 hours, all of the Daphnia at 1.0 mg/L were mobile. Based on this result, the definitive (limit) test employed an initial nominal concentration of 1.0 mg/L.
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
NOELR
Effect conc.:
> 0.022 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
No immobilisation or adverse effects on the Daphnia were noted. Based on this finding, the 48-hour EC50 could not be identified and the no-observed-effect concentration/loading rate was taken to be 0.0219/1.0 mg/L.
Results with reference substance (positive control):
Reference substance not tested
Reported statistics and error estimates:
Not applicable (limit test)

The measured concentrations of [1,3(or 1,4)-Phenylenebis(1-methylethylidene)]bis[tertbutyl] peroxide ranged between 0.0212 and 0.0225 mg/L at the start of the test. After 48 hours, no test substance was detected (limit of detection 0.01 mg/L), confirming all of the

parent substance had degraded. Consequently, test results were expressed in terms of the mean level of test substance measured at the start of the test (0.0219 mg/L). This data was not unexpected in view of the low aqueous solubility of the test material.

Validity criteria fulfilled:
yes
Conclusions:
[1,3(or 1,4)-Phenylenebis(1-methylethylidene)]bis[tert-butyl]peroxide was not found to be acutely toxic to Daphnia magna when dispersed in water at a nominal loading rate of 1.0 mg/L equivalent to an initial mean measured concentration of 0.0219 mg/L.
Consequently, the 48-hour EC50 value for [1,3(or 1,4)-Phenylenebis(1-methylethylidene)]bis[tert-butyl]peroxide could not be calculated but must be >1.0 mg/L (>0.0219 mg/L). The “no observed effect loading rate” was 1.0 mg/L (0.0219 mg/L as initial mean measured concentration).
Executive summary:

The acute toxicity of [1,3(or 1,4)-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide was evaluated with Daphnia magna in a study performed in accordance with OECD testing guideline 202 and GLP requirements.

The young daphnids were exposed to nominal test concentrations of 1 mg/L under static conditions during 48 hours. The mean measured concentrations were not maintained between 80 and 120 % of nominal.

Mortality in control, temperatures, pH range and dissolved oxygen concentration were reported and in agreement with the guideline requirements.

The test substance was not found to be acutely toxic to Daphnia magna at a nominal loading rate of 1.0 mg/L, equivalent to an initial mean measured concentration of 0.0219 mg/L.

Description of key information

Analogous substance 25155-25-3 [1,3(or 1,4)-Phenylenebis(1-methylethylidene)]bis[tert-butyl]peroxide was not found to be acutely toxic to Daphnia magna when dispersed in water at a nominal loading rate of 1.0 mg/L equivalent to an initial mean measured concentration of 0.0219 mg/L.

Consequently, the 48-hour EC50 value for [1,3(or 1,4)-Phenylenebis(1-methylethylidene)]bis[tert-butyl]peroxide could not be calculated but must be >1.0 mg/L (>0.0219 mg/L). The “no observed effect loading rate” was 1.0 mg/L (0.0219 mg/L as initial mean measured concentration).

Key value for chemical safety assessment

Additional information

The acute toxicity of analogous 25155 -25 -3 [1,3(or 1,4)-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide was evaluated with Daphnia magna in a study performed in accordance with OECD testing guideline 202 and GLP requirements.

The young daphnids were exposed to nominal test concentrations of 1 mg/L under static conditions during 48 hours. The mean measured concentrations were not maintained between 80 and 120 % of nominal.

Mortality in control, temperatures, pH range and dissolved oxygen concentration were reported and in agreement with the guideline requirements.

The test substance was not found to be acutely toxic to Daphnia magna at a nominal loading rate of 1.0 mg/L, equivalent to an initial mean measured concentration of 0.0219 mg/L.