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Toxicity to soil macroorganisms except arthropods

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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:
guideline study with acceptable restrictions
Remarks:
Guideline study but it is not certain whether the study was conducted in accordance with GLP.
Qualifier:
according to
Guideline:
other: Environment Canada, EPS 1/RM/43, June 2004
GLP compliance:
not specified
Remarks:
The data is from a publication and this information was not included.
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 analysed 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 obtained 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 10% 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 analysed 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 ± 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 of juveniles produced was counted, and the juvenile dry biomass measured and recorded.
Nominal and measured concentrations:
Nominal/measured concentrations (mg/kg dry wt.) of D5 for this test were 0/0, 143/50, 244/91, 414/135, 704/248, 1197/358, 2035/507, 3460/1093, 5882/2362 and 10000/4074.
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 difference 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.
Endpoint:
toxicity to soil macroorganisms except arthropods: long-term
Type of information:
experimental study planned (based on read-across)
Study period:
After approval by ECHA
Justification for type of information:
See IUCLID Sections 6.0 and 6.3 (CSR Sections 7.0 and 7.2) for discussion and justification of read-across.
Qualifier:
according to
Guideline:
OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))
Principles of method if other than guideline:
The registrants recommend that the stability of test substance concentrations in the soil under realistic test conditions must be explored as part of method development. Subsequent toxicity testing is subject to satisfactory results from the stability studies.

Description of key information

28-day LC50: >4074 mg/kg dry weight and 56-day NOEC ≥4074 mg/kg dry weight, for the effects of D5 on mortality and reproduction and growth respectively of Eisenia andrei.

Key value for chemical safety assessment

Additional information

There are no data describing the long-term toxicity of the registration substance to soil macroorganisms except arthropods. Earthworm reproduction studies are proposed for the structural analogue, silsesquioxanes, phenyl (CAS 70131-69-0).

In the interim period, before the data with phenyl silsesquioxanes become available, data are available for the siloxane decamethylcyclopentasiloxane (D5, CAS 541-02-6).

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.

No effects at the highest concentration tested were also determined in a second test with D5: 28-d F0 LC50 values  of >76 mg/kg nominal concentration, >41 mg/kg mean measured concentration, and NOECs of 76 mg/kg nominal concentration, and 41 mg/kg mean measured concentration, have been determined for effects of D5 on survival and weight change of adult earthworms.

56-d F1 LC50 values  of >76 mg/kg nominal concentration, >41 mg/kg mean measured concentration, and NOECs of 76 mg/kg nominal concentration, and 41 mg/kg mean measured concentration, have been determined for effects of D5 on reproduction of the earthworm Eisenia fetida.

Read-across of the terrestrial toxicity data for D5 to Reaction Mass of 3,3-diphenylhexamethyltrisiloxane and 3,3,5,5-tetraphenylhexamethyltetrasiloxane (CAS 352230-22-9) is considered to be suitable to derive an interim hazard and risk assessment under REACH for the registration substance.

Refer to Sections 6.0 and 6.3 for further discussion.