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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The result was obtained by an appropriate predictive method.
Principles of method if other than guideline:
The ECOSAR ‘neutral organics’ QSARs for acute data have been applied and the effect concentrations calculated using log Kow and molar mass as input variables. An additional factor of *0.2 has been applied to the results.


The USEPA model ECOSAR was used as the basis for the estimation. This method is well-validated for ‘neutral organics’, i.e. those which act by a general narcotic mechanism, the potency of which is usually related to log Kow. Its scope is acute and long-term effects for the three standard trophic levels.
The method was validated for use with organosilicon compounds with a high weight percent of Si and limited or no additional functionality. Many of the reliable data for the category are limit values, therefore, the data were considered in terms of the range of theE(L)C50, in accordance with normal classification bands:    
E(L)C50 < 1 mg/l;
E(L)C50 in the range > 1 mg/l to 10 mg/l;
E(L)C50 in the range > 10 mg/l to 100 mg/l;
E(L)C50 > 100 mg/l.

In broad terms ECOSAR predicted correctly for most substances for each trophic level. However, performance was improved significantly by application of a factor of 0.2 to each predicted value (expressed in mg/l). This is equivalent to saying that the organosilicon substances are slightly more toxic than the general ECOSAR ‘neutral organics’ regression lines, although still well within the range of each model. The factor of 0.2 is applicable to fish,Daphniaand algae, across the whole range of log Kowvalues.
It is concluded that the acute effects of the substances in the sub-category can therefore be predicted from ECOSAR, with a minor modification.
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
600 mg/L
Conclusions:
A 48 h LC50 value of 600 mg/L was obtained for the hydrolysis product of the submission substance using an appropriate calculation method. The results are considered to be reliable.
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2002-03-22 to 2002-08-08
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Nominal concentrations: 0(Control). 0.464, 1.00, 2.15, 4.64, 10.0, 21.5, 46.4 and 100 mg/L.

- Sampling method: An aliquot of test medium from all test concentrations at the start of the test before filling the test vessels. A combined aliquot was collected from the test media from all four exposure vessels of all test concentrations at the end of the test (48 hours).

- Sample storage conditions before analysis: All samples were stored at -20ºC prior to analysis.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A 100 mg/L stock solution was prepared by adding 100 mg of the substance to 1 litre of dilution water and stirring intensely for 30 minutes. Lower concentrations were prepared by dilution of the stock solution.

- Controls: Dilution water
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM

- Source: Laboratory culture derived originally from IRChA, France

- Age at study initiation (mean and range, SD): 6-24 hours

- Method of breeding:

- Feeding during test: none

ACCLIMATION

- Acclimation conditions (same as test or not): yes

- Type and amount of food: Unicellular algae (Scenedesmus subspicatus) and small amount of aerated sewage.

- Feeding frequency: No data
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
250 mg/l as CaCO3
Test temperature:
20 +/-1ºC
pH:
7.66-8.54
Dissolved oxygen:
≥70% ASV
Nominal and measured concentrations:
Nominal concentrations: 0(Control). 0.464, 1.00, 2.15, 4.64, 10.0, 21.5, 46.4 and 100 mg/L.

Measured DOC concentrations were within 20% of the theoretical values at both the start and end of the test. The test results are therefore expressed and interpreted with reference to the nominal concentrations.
Details on test conditions:
TEST SYSTEM

- Test vessel:

- Type: no data

- Material, size: glass, 50 mL

- Aeration: none

- Renewal rate of test solution (frequency/flow rate): static test

- No. of organisms per vessel: 5

- No. of vessels per concentration (replicates): 4

- No. of vessels per control (replicates): 4

- Biomass loading rate: 1 daphnid/10 mL

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Reconstituted fresh water prepared by adding salts to demineralised water.

- Alkalinity: 0.8 mmol/L

- Ca/mg ratio: 4:1

- Culture medium different from test medium: no

- Intervals of water quality measurement: Start and end of test

OTHER TEST CONDITIONS

- Adjustment of pH: no

- Photoperiod: 16 hours light, 8 hours dark

- Light intensity:500 lux (+/-20%)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mobility after 24 and 48 hours

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2.2

- Range finding study: no
Reference substance (positive control):
no
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
37 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
62 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
2.15 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
- Immobilisation of control: 2.5%
Reported statistics and error estimates:
The EC50 values were calculated by linear regression analysis employing probit analysis (Probit Program Version 1.5, U.S. Environmental Protection Agency, 1992). The NOEC values were based directly on examination of the raw data.

Table 1. Test results

 Nominal test substance concentration (mg/L)  Mean percentage immobilisation after 24 hours  Mean percentage immobilisation after 48 hours
 0 (Control)  0  2.5
 0.464  0  0
 1.00  0  0
 2.15  0  0
 4.64  5  20
 10.0  20  35
 21.5  5  20
 46.4  5  25
 100  95  100

Table 2. Results of analysis of test media

 Nominal test substance concentration (mg/l)  Theoretical DOC concentration (mg/L)  Actual DOC concentration at start of test (mg/L) Actual DOC concentration at end of test (mg/L) 
 0.464  0.28  <0.5  <0.5
 1.00  0.60  <0.5  <0.5
 2.15  1.29  1.5  1.5
 4.64  2.78  3.0  2.9
 10.0  6.00  5.9  6.2
 21.5  12.9  12.9  13.1
 46.4  27.8  28.5  27.5
 100  60.0  62.5  59.5
Validity criteria fulfilled:
yes
Conclusions:
A 48-h EC50 value of 37 mg/L and NOEC of 2.15 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna. It is very likely that the test organisms were exposed to the hydrolysis products of the substance.
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2009-10-28 to 2009-10-30
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Sampling method: At test initiation, samples were removed from the intermediate mixing vessels for analysis of the hydrolysation product (trihydroxy(phenyl)silane). At test termination, the replicate solutions from the treatment levels and the control were composited within the treatments prior to sampling.
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Prior to test solution preparation, a dosing stock solution was prepared by mixing 304 μL of Trichloro(phenyl)silane with 400 μL of tetrahydrofuran (THF) using a Hamilton syringe. A 100 mg test item/L stock solution was prepared prior to test initiation by adding 352 μL of the dosing stock solution to 1600 mL dilution water using a Hamilton syringe. Prior to addition of the dosing stock solution, the glass beaker containing the dilution water was placed on a magnetic stirrer. The spiked solution was stirred continuously over night. The pH of the solution was then adjusted to 7.01 with 1 N hydrochloric acid (HCl) and 1 N sodium hydroxide (NaOH). Thereafter, the stock solution was further diluted to a final volume of 2000 mL with dilution water, resulting in a solvent (THF) concentration of 0.10 mL/L. Nominal concentrations of 2.0, 4.3, 9.4, 20.7, 45.5 and 100 mg/L were prepared by diltion of the stock solution. and addition of THF to a final concentration of 0.1 mL/L. All resulting test solutions were shaken by hand for 30 seconds and observed to be clear and colorless, with no visible undissolved test item.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM

- Source: The Daphnia magna used in this toxicity test were obtained from laboratory cultures maintained at Springborn Smithers Laboratories (Europe), originally obtained from a culture at Springborn Smithers Laboratories Wareham (MA), USA.

- Culture conditions: Prior to testing, the daphnids were held in glass beakers under a photoperiod of 16 hours light and 8 hours darkness with a 30 minute transition period.

- Culture medium: The culture water consisted of modified Elendt M4 medium. After preparation the medium was aerated using an air pump to bring the pH and dissolved gases into equilibrium with the atmosphere. The modified Elendt M4 medium was allowed to equilibrate for at least two days prior to use. Total hardness, total alkalinity, pH and specific conductivity of the dilution water were determined after preparing each batch to verify that these parameters are within the acceptable ranges.

- Feeding: During culture the daphnids were fed 1.5 - 2.0 mL of a solution containing approximately 4 x 107 cells/mL of the unicellular green alga, Ankistrodesmus falcatus (ANK) and approximately four drops or 0.5 mL of a combination of yeast, cereal leaves and flaked fish food (YCT) daily.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
150 mg/L as CaCO3
Test temperature:
19.1 to 21.2°C
pH:
7.31 to 7.94
Dissolved oxygen:
8.00 to 8.61 mg/L
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal test concentrations: 0 (Control), 0 (solvent control), 2.0, 4.3, 9.4, 20.7, 45.5 and 100 mg/L

The concentration of the test item (determined as trihydroxy(phenyl)silane) in the newly prepared solutions at test start ranged from 92.9 to 103% of nominal concentrations. The concentration of the test item in the aged solutions at test termination (hour 48) ranged from 92.9 to 104% of nominal concentrations.

Based on these results, the nominal test concentrations were used for the evaluation of the biological data.
Details on test conditions:
TEST SYSTEM

- Replication: Four test vessels per treatment level and the controls were prepared.

- Age of test organisms: Daphnids, < 24 hours old

- Distribution of test organisms to treatments: Daphnids were impartially selected and distributed using an intermediate vessel by adding no more than two daphnids to each vessel until all intermediate vessels contained two daphnids. This procedure was repeated until each vessel contained 20 daphnids. The test was initiated when 5 daphnids were introduced to each replicate exposure vessel (replicates A to D). A total of 20 organisms were exposed to each treatment level and control solutions. Each test vessel was labeled with the study number, concentration and replicate designation.

- Feeding: The daphnids were not fed during the 48 hour exposure period.

- Dilution water: The batch of modified Elendt M4 medium used for the definitive test had a total hardness and alkalinity of 150 and 34 mg/L as CaCO3, respectively, a pH of 8.05 and a specific conductivity of 400 μS/cm.

- Observations: The number of immobilized daphnids observed in each replicate test vessel was recorded at test initiation and after 24 and 48 hours of exposure. Immobilization was defined as those animals not able to swim within 15 seconds after gentle agitation of the test vessel or by pipette. Biological observations (e.g., abnormal behavior or appearance of the test organisms) and observations of the physical characteristics of the test solutions (e.g., precipitate, film on the surface of the test solution) were also made and recorded after 0, 24 and 48 hours of exposure.

- Water quality: The pH, dissolved oxygen (DO) concentration and temperature were measured at 0, 24 and 48 hours in one replicate of each treatment level and the control. Continuous temperature monitoring was performed in an additional vessel adjacent to the test vessels throughout the exposure period. The pH was measured with a WTW 323 pH meter, dissolved oxygen and daily temperature were measured using a WTW Oxi 325 dissolved oxygen meter. Light intensity was measured with a Pancontrol LX 1308 lux meter.
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
9.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
- Immobilisation of Control: 0 in Control, 5% in solvent Control
Reported statistics and error estimates:
There were insufficient levels of immobilisation in the treatments to derive an EC50 value.

The No-Observed-Effect Concentration (NOEC) was determined by visual observation of the raw data and is defined as the highest concentration tested at which there was no toxicant-related immobilization or physical and behavioral abnormalities (e.g., lethargy) with respect to the control organisms.

Table 1. Results of analysis of test media (measured as Trihydroxy(phenyl)silane)

 Nominal test substance concentration (mg/L)  Initial measured concentration (mg/L) and (Percentage of nominal) Measured concentration after 48 hours (mg/L) and (Percentage of nominal) 
 0 (Control)  <LOQ  <LOQ
 0 (Solvent control)  <LOQ  <LOQ
 2.0  1.86 (92.9)  1.86 (92.9)
 4.3  4.22 (98.1)  4.18 (97.1)
 9.4  9.22 (98.1)  9.49 (101)
 20.7  20.5 (99.0)  20.5 (99.2)
 45.5  46.8 (103)  47.5 (104)
 100  99.0 (99.0)  97.6 (97.6)

Table 2. Test results

 Nominal test substance concentration (mg/L)  Mean percentage immobilisation after 24 hours  Mean percentage immobilisation after 48 hours
 0 (Control)  0  0
 0 (Solvent control)  0  5
 2.0  0  0
 4.3  0  5
 9.4  0  0
 20.7  0  15
 45.5  0  15
 100  0  25
Validity criteria fulfilled:
yes
Conclusions:
A 48-hour EC50 value of >100 mg/L and a NOEC of 9.4 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna. It is likely that the test organisms were predominantly exposed to the hydrolysis products of the test substance.
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.
Reason / purpose:
read-across source
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
9.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility

Description of key information

A 48-h EC50 value of 37 mg/L and NOEC of 2.15 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna based on nominal concentrations.

QSAR (96-h) EC50 of 600 mg/l derived for the hydrolysis product, phenylsilanetriol

Key value for chemical safety assessment

Additional information

Acute aquatic toxicity to invertebrates has been investigated for triethoxy(phenyl)silane (CAS 780-69-8) according to OECD 202. Daphnia magna was exposed for 48 h under static conditions (2003). The 48-h EC50 value for Daphnia magna exposed to triethoxy(phenyl)silane (CAS 780-69-8) was 37 mg/L (nominal).

Since the substance hydrolyses rapidly it is very likely that the test organisms were exposed to the hydrolysis product. Therefore further read across data from the structurally analogous substance, trichloro(phenyl)silane (CAS 98-13-5) were used as supporting information, as both substances hydrolyse rapidly to the same silanol hydrolysis product phenylsilanetriol. Details on read across justifications can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13. The study (2009) with the read across substance showed no effects towards Daphnia magna at the highest concentration tested of 100 mg/L (OECD Guideline 202).

Additionally an EC50 of 600 mg/L was derived for the hydrolysis product, based on an appropriate calculation method.