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Ecotoxicological information

Long-term toxicity to aquatic invertebrates

Administrative data

long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
equivalent or similar to guideline
other: ISO. 2008. IS 20665:2008: Water quality – Determination of chronic toxicity to Ceriodaphnia dubia. International Organization for Standardization, Geneva.
GLP compliance:

Test material

Constituent 1
Chemical structure
Reference substance name:
Tetrakis(2-ethylbutyl) orthosilicate
EC Number:
EC Name:
Tetrakis(2-ethylbutyl) orthosilicate
Cas Number:
Molecular formula:
tetrakis(2-ethylbutyl) orthosilicate
Test material form:
Details on test material:
Tetrakis(2-ethylbutyl) Orthosilicate
CAS 78-13-7
Expiration: May 2020
Clear colorless liquid

Sampling and analysis

Analytical monitoring:
TOC analysis
Details on sampling:
Total organic carbon (TOC) analysis of the test solutions was performed on fresh solutions (Day 0 and 5) and corresponding “old” solutions (Day 1 and 6).

Test solutions

Details on test solutions:
A water accommodated fraction (WAF) was prepared on day -1 by adding 4.5 µL of test substance using a glass and stainless steel syringe to 4 L of dilution water in a glass 4L aspirator bottle to achieve a nominal loading of ~1.0 mg/L. A control WAF was prepared in the same manner without the addition of test substance. Each 4 L aspirator bottle was closed with a Teflon® screw plug. For the treatment containing test substance, the volume of test substance dispensed into the aspirator bottle was calculated using a nominal loading of 1.0 mg/L, density, and the volume of dilution water. Both treatment and control WAFs were mixed with a Teflon®-coated stir bar on a magnetic stir plate. The vortex was set at 10% of the static liquid depth for each WAF. Each WAF mixed for 24.5 hours at approximately test temperature (25° ± 2°C) prior to study initiation. At the end of the mixing period, each WAF was allowed to settle for 0.75 hour (±15 minutes). At the end of the settling period, separate samples of the control and treatment WAF were removed from the mixing vessel through the outlet at the bottom of the vessel and added to each corresponding replicate vial. Following the removal of daily exposure solutions from the control and treatment WAF, the WAFs were returned to the magnetic stir plates and began mixing again as previously described. This method was repeated for all daily renewals.

Test organisms

Test organisms (species):
Ceriodaphnia dubia

Study design

Test type:
Water media type:
Limit test:
Total exposure duration:
7 d
Remarks on exposure duration:
Ten replicates of one C. dubia neonate were added to 20 mL scintillation vials. Dyring daily renewal of test solutions the neonates were counted and the adults observed for survival, until 60% of the control produced 3-broods.

Test conditions

Test temperature:
25.4 to 25.6 ºC
Dissolved oxygen:
Dissolved oxygen (DO) remained ≥7.34 mg/L throughout the test.
Details on test conditions:
The photoperiod was 16 hours light and 8 hours of dark with an intensity ranging from 797 - 1096 lux during the exposure period provided by cool white fluorescent bulbs.

Results and discussion

Effect concentrations
Key result
7 d
Dose descriptor:
Effect conc.:
> 1
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
Remarks on result:
not determinable
Reported statistics and error estimates:
The chronic endpoint was calculated using reproduction data gathered throughout the duration of the study. Data was centralized amongst individual treatment groups prior to running a normality test (US EPA). The Shapiro-Wilk goodness of fit test was used to determine that the data was normally distributed (Shapiro and Wilk, 1965). A one-way analysis of % inhibition by comparing the sum of three broods to the control treatment determined a NOEL using the parametric Dunnetts, with control method for mean comparison . All chronic endpoints were evaluated using JMP v. 13

Applicant's summary and conclusion

Validity criteria fulfilled:
A no observable effect loading (NOEL) for this test was based on a limit test of 1 mg/L. No statistical difference between control and test organisms reproductive rates were found, therefore, the NOEL was >1 mg/L.