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Toxicity to terrestrial arthropods

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Endpoint:
toxicity to terrestrial arthropods: long-term
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:
Endpoint:
toxicity to terrestrial 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 mot 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:
other: Environment Canada 1/RM/47, June 2007
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
Application method:
soil
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):
Folsomia candida
Animal group:
Collembola (soil-dwelling springtail)
Details on test organisms:
Ten age-synchronized organisms {10-12 d old) were added to each test vessel at the test start (day 0).
Study type:
laboratory study
Limit test:
no
Total exposure duration:
28 d
Test temperature:
20+/-2°C
pH (if soil or dung study):
7.55 +/-0.15
Photoperiod and lighting:
8.3 +/-2.1 μmol(m2/s)
Details on test conditions:
Ten age-synchronized organisms {10-12 d old) were added to each test vessel at the test start (day 0). The test vessels were incubated at20 +/-2°C with an average light intensity of 8.3 +/-2.1 μmol(m2/s), within the ranges specified in the method. The test vessels were aerated weekly, fed yeast bi-weekly, and the soil was hydrated with de-ionized water as necessary. At the end of the test, the test vessels were flooded with water, allowing the test organisms to float to the surface, and the number of live adults and juveniles was recorded.
Nominal and measured concentrations:
Nominal concentrations (mg/kg dry wt.) of D5 used in the F. candida test were 0, 175, 279, 447, 715, 1144, 1831, 2930, 4688, 7500.

Measured concentrations (mg/kg dry wt.) of D5 used in the F. candida test were 0.10, 42, 65, 99, 239, 377, 363, 1082, 2053, 2917. The measured value of 0.10 mg/kg D5 in the control soil was used as the background level.
Reference substance (positive control):
not specified
Duration:
28 d
Dose descriptor:
LC50
Effect conc.:
813 mg/kg soil dw
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: 457-1514
Duration:
28 d
Dose descriptor:
other: IC50
Effect conc.:
767 mg/kg soil dw
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
reproduction
Remarks on result:
other: 471-1253
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
377 mg/kg soil dw
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
other: mortality and reproduction
Remarks on result:
other: based on visual evaluation of data by reviewer
Details on results:
An effect was observed for both adult survival and juvenile reproduction when F. candida was exposed to D5. There was no significant difference between the test endpoints, in that, as adults became affected by D5 in the soil, the juvenile production dropped of accordingly.
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.

A NOEC has been determined by the reviewer on the basis of a visual examination of the data.
Validity criteria fulfilled:
yes
Conclusions:
A 28-day LC50 value of 813 mg/kg dry weight and a 28 day IC50 value of 767 mg/kg dry weight have been determined for the effects of the test substance on mortality and reproduction of Folsomia candida. A NOEC of 377 mg/kg dry weight has been determined by the reviewer on the basis of a visual examination of the data for both mortality and reproduction.

Description of key information

LC50 (28 day): 813 mg/kg dry weight, mortality Folsomia candida, measured, read-across from D5, CAS 541-02-6;

IC50 (28 day): 767 mg/kg dry weight reproduction, Folsomia candida, measured, read-across from D5, CAS 541-02-6;

NOEC (28 day): 377 mg/kg dry weight mortality and reproduction, Folsomia candida, measured, read-across from D5, CAS 541-02-6.

Further soil testing is being carried out with the registered substance.

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil dwelling arthropods:
377 mg/kg soil dw

Additional information

There are no data describing the long-term toxicity of the registered substance to terrestrial arthropods.

An OECD TG 222 earthworm reproduction study is planned for the registration substance. The earthworm is the standard organism for soil macroorganisms and there is no indication that arthropods would be any more susceptible.

A terrestrial arthropod toxicity test is therefore not required.

However, 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 813 mg/kg dry weight and a 28 day IC50 value of 767 mg/kg dry weight have been determined for the effects of D5 on mortality and reproduction of Folsomia candida. A NOEC of 377 mg/kg dry weight has been determined by the reviewer on the basis of a visual examination of the data for both mortality and reproduction. This data will be considered in the derivation of the PNECsoil for ViM4Q.

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.