Octaphenylcyclotetrasiloxane

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

See endpoint summary for justification of read-across

Reason / purpose for cross-reference:

read-across source

Duration:

56 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Remarks:

as earthworm weight

Duration:

56 d

Dose descriptor:

EC10

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

56 d

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Description of key information

NOEC, EC10 and EC50 (56-d): ≥1000, >1000 and >1000 mg/kg dwt (nominal), reproduction,Eisenia fetida

NOEC, LC50 (28-d): ≥1000 and >1000 mg/kg dwt (nominal), survival and growth (as weight),Eisenia fetida, read-across from an analogous substance, phenyl silsesquioxanes (EC 939-487-8) within the Reconsile Siloxanes Category.

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:

556 mg/kg soil dw

Long-term EC10, LC10 or NOEC for soil macroorganisms:

556 mg/kg soil dw

Additional information

There are no data describing the long-term toxicity of the registration substance to soil macroorganisms. However, data are available within the Siloxanes Category for the analogue substance, phenyl silsesquioxanes (EC 939-487-8).

56-day NOEC, EC10 and EC50 values of ≥1000, >1000 and >1000 mg/kg dwt respectively, have been determined for the effects on the reproduction of Eisenia fetida, based on nominal concentrations. 28-day NOEC and LC50 values of ≥1000 and >1000 mg/kg dwt have been determined for the survival and growth (as weight) of Eisenia fetida, based on nominal concentrations. These results are equivalent to ≥556, >556 and >556 mg/kg dwt respectively, when normalised to 2% organic carbon content.

Effect concentration values have been reported in terms of nominal concentrations because the measured concentrations were within 80% of nominal.

Due to the potential volatility of the read-across substance, a stability trial under OECD 222 conditions was carried out prior to the above study.

The stability assessment was executed over a 56 day period using [14C] radiolabelled phenyl silsesquioxanes test substance. The trial was carried out under OECD 222 test conditions, in natural soil, but without test organisms.

The test substance was mixed into natural soil and chemical analysis was performed by taking triplicate soil cores from one of the treated replicates at Days 0, 3, 7, 14, 28, and 56 and analysed by liquid scintillation counting (LSC) and high-performance liquid chromatography with radiometric detection (HPLC-RAM).

The measured dosing stock concentration was 414 mg/kg dry weight soil.

The measured applied test concentration was 381 mg/kg dry weight soil.

The test substance was determined to be stable in natural soil. This was based on the material balance remaining at or above 100 % AR (103 -107% of applied radioactivity) and the HPLC distribution of radioactivity showing similar chromatographic profiles (83.6 to 88.2%) over the 56 day study.

Further details are reported in the stability assessment EPSR (Smithers, 2020).

Refer to Section 6.3 for further discussion.