3,3-bis[(dimethylvinylsilyl)oxy]-1,1,5,5-tetramethyl-1,5-divinyltrisiloxane

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Data waiving:

other justification

Justification for data waiving:

other:

Qualifier:

according to guideline

Guideline:

OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))

Reference 2

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study but it is not certain whether the study was conducted in accordance with GLP. The read-across of the data is considered to be reliability 2.

Qualifier:

according to guideline

Guideline:

other: Environment Canada, EPS 1/RM/43, June 2004

GLP compliance:

not specified

Remarks:

The study is reported in a publication, which doesn't make it clear whether or not the test was performed under GLP

Analytical monitoring:

yes

Details on sampling:

Soil samples were collected throughout the initial treatment, preparation (i.e., at manure amendment, following the 2-h equilibrium period, and following mixing of the amended biosolid with the Gr10 soil) for the range-finding tests to confirm the analytical methodology used, as well as to evaluate the loss of D5 over time. For the definitive tests, samples were taken for analysis only on day 0 of the test (i.e., when the test organisms were added) to confirm dose concentrations in the test soil. All samples were immediately frozen and stored at -20°C prior to analysis. All samples were analyzed for cVMS D4, D5 and D6 concurrently by Quebec Laboratory for Environmental Testing of Environment Canada (Montreal, Quebec).

Triplicate 1.0g (+/-0.2) (wet weight) samples were then measured into glass tubes and well mixed to ensure solids are homogenized. To extract the soil samples, 5 mL of acetonitrile was added to each sample and vortexed followed by the addition of 5 mL of pentane (also vortexed). The sample was then sonicated in an ice bath for 10 min followed by centrifugation at 1500 RPM for 10 min at 15°C. The pentane phase was then transferred to a clean GC vial and 75 μL of naphthalene-D8 solution(lfi) ng/μL in pentane) was added as an internal standard.

Vehicle:

no

Details on preparation and application of test substrate:

A sandy loam soil (Gr10) was obained from Greely Sand and Gravel (Ottawa Ontario (ON)) in June 2010 and was dried, sieved (4-mm mesh) and homogenized prior to use. The negative control treatment consisted of a formulated artificial soil (AS) comprising 101 air-dried pre-sieved Sphagnum sp. peat, 20% kaolin clay, and 70% silica sand, with calcium carbonate added to standardize the soil pH.

For the toxicity tests, the soil was amended with either an uncontaminated or contaminated surrogate biosolid. Although available, the use of an actual biosolid produced from a water treatment facility was not pursued as an option for use in the toxicity tests as the potential for other contaminants or toxicants present in the sample may have confounded toxicity test results. As a result, mushroom compost and organic cow manure were both considered as options for a surrogate biosolid. Both alternative biosolids were analyzed in conjunction with a real biosolid (obtained from the Robert O. Picard Water Treatment facility in Ottawa, ON) for comparison of their physical and chemical characteristics. Based on these characteristics. the organic cow manure was selected for its similarity in percent organic matter to the actual biosolid.

To prepare test samples, the surrogate biosolid was amended with D5 (97% pure liquid; Sigma-Aldrich) to create a contaminated test substance; subsequently, the amended biosolid was manually mixed for 2 min, covered to prevent volatilization, and allowed to equilibrate for 2 h. Following the 2 h equilibration period, the amended biosolid was added to the Gr10 soil at a rate of 5 g/kg (on a dry weight basis), equivalent to 8 t/ha, a common application rate for biosolids on agricultural soils in Ontario to create the test soil. Each test concentration was prepared independently. The average moisture content of the test soil was 38 t 3%, with an average pH of 7.55+/-0.15 for all test set-ups.

Test organisms (species):

other: Eisenia andrei

Animal group:

annelids

Details on test organisms:

Two sexually mature adults were added to each test vessel at the start of the test (day 0), and the average initial wet weight of the adult earthworm
was 451.7 +/-108.2 mg.

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Total exposure duration:

56 d

Test temperature:

20 +/-2°C

pH:

7.55 +/-0.15

Details on test conditions:

Test vessels were incubated at 20+/-2°C with an average light intensity of 10.7 +/-2.5 μmol/(m2 t)-1. within the ranges specified in the earthworm method; and food (cooked oatmeal) was added on days 0,14,28 and 42 of the test. On day 28, surviving adults were counted and removed from the test soil, and on day 56. the number ofjuveniles produced was counted, and the juvenile dry biomass measured and recorded.

Nominal and measured concentrations:

Nominal concentrations (mg/kg dry wt.) of D5 for this test were 0, 143, 244, 414, 704, 1197, 2035, 3460, 5882 and 10000.

Measured concentrations (mg/kg dry wt.) of D5 for this test were 0, 50, 91, 135, 248, 358, 507, 1093, 2362 and 4074.

Reference substance (positive control):

not specified

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

> 4 074 mg/kg soil dw

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

56 d

Dose descriptor:

other: IC50

Effect conc.:

> 4 074 mg/kg soil dw

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

56 d

Dose descriptor:

other: IC50

Effect conc.:

> 4 074 mg/kg soil dw

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

other: individual juvenile dry mass

Details on results:

There was no efiect on adult survival after 28 d of exposure (100% survival in all treatments, data not shown). While there was a significant reduction in juvenile production at test concentrations ≥507 mg/kg (Fisher's LSD; p<0.05), the lC50 was >4074 mg/kg. There was also no effect on the mean individual dry mass of juveniles; however, the mass increased with increasing exposure to D5. This may be due to less competition for resources (i.e., food) within the test vessel as fewer juveniles were observed at higher test concentrations. Test concentrations > 1093 mg/kg had significantly higher mean individual dry mass compared with lower test cocentrations (Fisher's LSD: p < 0.05).

Reported statistics and error estimates:

The lethal concentration (i.e., LC50s) was calculated for invertebrate mortality using the EPA Probit Analysis Program {version 1.5) or the EPA Trimmed Spearman-Karber (TSK) Program (version 1.5). Inhibitory concentrations (i.e., lC50s) were estimated for invertebrate juvenile production using nonlinear regression analysis via SYSTAT (version 13) software, ensuring that model assumptions (normality and homoscedasticity) were met. When regression models were unable to calculate the IC50, or model assumptions were not met, a "Linear Interpolation for Sublethal Toxicity: The Inhibition Concentration (ICp) Approach" (ICPIN) (version 2.0) was used. ln cases where a 50% effect was not observed, an ANOVA was performed to determine if there was a significant difference in the measured endpoint across treatments. lf a significant difference was found. then Fishers least significant difference test was used to determine where the difierence was among treatments.

Validity criteria fulfilled:

yes

Conclusions:

A 28-day LC50 value of >4074 mg/kg dry weight and a 56-day NOEC of ≥4074 mg/kg dry weight have been determined for the effects of the test substance on mortality and reproduction and growth respectively of Eisenia andrei.

Description of key information

LC₅₀ (28 day): >4074 mg/kg dry weight, Eisenia andrei, read-across from D5, CAS 541-02-6

NOEC (56 day): ≥4074 mg/kg dry weight, reproduction and growth respectively, Eisenia andrei, read-across from D5, CAS 541-02-6

Additional information

There are currently no reliable data describing the long-term toxicity of the registered substance to soil macroorganisms.

An OECD TG 222 earthworm reproduction test is being conducted with the registration substance according to ECHA final decision TPE-D-2114422682-53-01/F. The substance dossier and risk assessment will be updated once results of the study are available and the study is finalised. Results of the test are expected in February 2021. Please see a letter from the testing laboratory, attached in Section 6.3.1 IUCLID Placeholder EPSR, for further details.

Due to the potential volatility of the registration substance, a stability trial under OECD 222 conditions was carried out.

The stability assessment was executed over a 56 day period 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 Day 0, 3, 7, 14, 28, and 56 and analysing by GC-MS.

The test substance was determined to be stable in natural soil based on mean analytical recoveries of 103% at day 28 for the 1000 mg/kg treatment level. The definitive OECD 222 Earthworm Reproduction Test with ViM4Q is therefore going to be conducted.

Until these data are available, terrestrial data have been read across from the siloxane decamethylcyclopentasiloxane (D5, CAS 541-02-6) to derive an interim PNECsoil for hazard assessment.

A 28 day LC₅₀ value of >4074 mg/kg dry weight and a 56 day NOEC of ≥4074 mg/kg dry weight have been determined for the effects of the test substance on mortality and reproduction and growth respectively of Eisenia andrei.

The registered substance and the surrogate substance share similar physico-chemical properties but are not close structural analogues (branched and cyclic siloxanes). Terrestrial testing is being carried out with the registered substance.

Read-across of the terrestrial toxicity data for D5 to ViM4Q is considered to be suitable to derive an interim hazard and risk assessment under REACH until terrestrial tests with the registration substance are available.