Triethoxyoctylsilane

Toxicity to terrestrial arthropods

Administrative data

Endpoint:

toxicity to non-target arthropods on natural substrate (NTA other than pollinators)

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14th of March 2020 to 15th of September 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 210 (Fish, Early-Life Stage Toxicity Test)

Version / remarks:

July, 2013

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Nominal concentrations: 0, 0.031, 0.063, 0.13, 0.25, 0.50 mg/L
Geometric mean measured concentration: 0, 0.0029, 0.0068, 0.011, 0.017, 0.036 mg/L
- Sampling method: Semi-static
- Sample storage conditions before analysis: Sample storage stability was not assessed.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
At the start of the test, groups of 20 eggs were added to glass scintillation vials half filled with treated mains water and each vial was randomly assigned to a test vessel.
The eggs were transferred using a discrete pipette into the test vessel. The eggs were released under the surface of the test media, as close to the bottom of the vessel as possible.
Observations were performed daily throughout the duration of the test and details of the following parameters were recorded:

• Hatching – number of larvae hatched until hatching was complete
• Egg mortalities – an egg was considered dead if it was observed to be cloudy or necrotic
• Fish mortalities – a larvae were considered dead if it did not respond to stimulus, via touch
• Sub-lethal effects including behavioural abnormalities (typical observations on appearance include size, paleness and any developmental effects such as spinal deformity or differences in body shape)
During the pre-hatch period, where possible, non-viable or necrotic eggs were removed, avoiding disturbance of adjacent viable eggs. The post-hatch phase started once all of the viable eggs were considered to have hatched in the control groups.

On Day 28 post-hatch, the total numbers of surviving larvae were counted and individual total fish lengths and wet weights of all remaining fish were determined. Prior to initial weighing, the fish were blotted dry to make sure that all surface water was removed.

The percentage post-hatch survival was determined by expressing the number of surviving larvae on Day 28 post-hatch as a percentage of the hatched larvae at Day 0 (post-hatch).

Test organisms (species):

Pimephales promelas

Details on test organisms:

TEST ORGANISM
- Common name: Fathead Minnow
- Strain: Pimephales promelas
- Source: From an in-house laboratory breeding system (Smithers ERS Limited)
- Age at study initiation (mean and range, SD):
- Length at study initiation (length definition, mean, range and SD):
- Weight at study initiation (mean and range, SD):
- Method of breeding:
- Feeding during test : The developing larvae were fed freshly cultured brine shrimp (Artemia salinis) nauplii. Surplus feed was siphoned from the test vessel on at least daily intervals during the test.
- Food type: Freshly cultured brine shrimp (Artemia salinis) nauplii.
- Amount: Twice daily, ad libitum.
- Frequency: Once hatching had started, the larvae were fed approximately 24-hour old shrimp. From Day 5 post-hatch and onwards, the larvae were fed approximately 48-hour old shrimp.

ACCLIMATION
- Acclimation period: At least one hour
- Acclimation conditions: According to laboratory conditions
- Type and amount of food: Not reported
- Feeding frequency during acclimation: Not reported
- Health during acclimation (any mortality observed): Not reported

Test type:

semi-static

Water media type:

freshwater

Remarks:

Treated mains water (treated via activated carbon particulate filter and ultraviolet irradiation).

Limit test:

no

Total exposure duration:

28 d

Remarks on exposure duration:

Duration was 13 days post-hatch.

Test temperature:

Water temperature: 23.5 to 25.4°C measured in the test vessels and 23.8 to 26.0°C for the continuously measured temperature.

pH:

7.21 to 7.84

Dissolved oxygen:

60.0 to 115.0% ASV (with one exception in a single vessel during the test which was 53.7%).

Nominal and measured concentrations:

Nominal concentrations: 0, 0.031, 0.063, 0.13, 0.25, 0.50 mg/L
Geometric mean measured concentration: 0, 0.0029, 0.0068, 0.011, 0.017, 0.036 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Size of vessel:
- Type (delete if not applicable): open / closed
- Material, size, headspace, fill volume:
- Aeration:
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate):
- No. of organisms per vessel:
- No. of vessels per concentration (replicates):
- No. of vessels per control (replicates):
- No. of vessels per vehicle control (replicates):
- Biomass loading rate:

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Treated mains water (treated via activated carbon particulate filter and ultraviolet irradiation).
- Total organic carbon: No reported
- Particulate matter: Not reported
- Metals: various values between <0.009 to <0.23 mg/L
- Pesticides: <0.005 μg/L and <0.007 μg/L for tecnazene
- Chloride: 13.6 mg/L
- Alkalinity (as CaCO3): 10.8 mg/L
- Ca/mg ratio: 14.2/2.2 mg/L
- Conductivity (electrical 20°C): 145 μS/cm
- Culture medium different from test medium: N/a
- Intervals of water quality measurement: Water temperatures, pH and dissolved oxygen concentrations were measured at the start and end of the test. Fresh and corresponding old media water qualities were also conducted at least weekly for the duration of the test. Fresh media water qualities were conducted on the bulk media, whereas old media water qualities were conducted on individual replicates.

OTHER TEST CONDITIONS
- Adjustment of pH: Not necessary as the range was 7.29 to 7.49
- Photoperiod: 16-hour light: 8-hour dark period with an approximate 30-minute dawn:dusk transition period.
- Light intensity: Not reported

EFFECT PARAMETERS MEASURED: N/a

TEST CONCENTRATIONS
- Spacing factor for test concentrations: N/a
- Justification for using less concentrations than requested by guideline: N/a

RANGE-FINDING STUDY
A solubility / stability trial was conducted in compliance with a separate GLP study to investigate the functional solubility of the test substance in dilution water and to determine the most appropriate dosing method. Based on the results, it was initially considered that the maximum functional solubility of the test substance in dilution water was 1.0 mg/L. Due to the limited functional solubility and instability of the test substance, it was believed that the semi-static exposure design would provide exposure to higher concentrations and a more consistent exposure pattern over the study period compared to flow-through design. Additionally, it was considered that the highest concentration of 1.0 mg/L used in the range-finding test was above the level of solubility of the test substance in dilution water. It was considered more realistic to have a concentration of 0.5 mg/L as this was estimated to be the maximum functional solubility of the test substance in treated mains water. Therefore, the final nominal concentrations were determined to be 0.031, 0.063, 0.13, 0.25 and 0.50 mg/L in the main test. Four replicates were prepared for the control, solvent control and each test concentration.

A range-finding test was conducted with a control, solvent control and nominal test substance concentrations of 0.0010, 0.010, 0.10 and 1.0 mg/L under semi-static conditions with daily renewal of the test media. Concentrations in excess of 1.0 mg/L were not tested at the request of the Sponsor as this was initially considered to be the limit of functional solubility of the test substance based on the solubility / stability trial. Single test vessels were prepared, with 10 eggs in each vessel, for the control, solvent control and each test concentration. The test duration was 13 days post-hatch.
- Results used to determine the conditions for the definitive study: Yes

Reference substance (positive control):

no

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

0.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: hatching success, normal larvae at hatch, posthatch survival and growth

Key result

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

> 0.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: hatching success, normal larvae at hatch, posthatch survival and growth

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

0.036 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: hatching success, normal larvae at hatch, posthatch survival and growth

Key result

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

> 0.036 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: hatching success, normal larvae at hatch, posthatch survival and growth

Details on results:

Analysis of the 4-hour old media on Day 0 (test start) showed a measured concentration of 68% of nominal for the 0.50 mg/L test concentration. This decreased to 33% of nominal after the first 24 hours of exposure (Day 1). On Day-0 post-hatch, the measured concentration in the 4-hour old media sample was 36% of nominal which decreased to less than the LOQ after 24-hours (Day-1 post-hatch). For the remainder of the test the 4-hour old sample results ranged from 8% to 24% of nominal with the 24-hour old samples generally less than the LOQ. These results showed the test substance was unstable in the test media but may also interact with biological material as the decrease in measured concentration over the 4- and 24hour periods increased as the organisms hatched and grew.

A similar trend in analytical measurements was observed for the remaining test concentrations.
Due to the decrease in measured concentration over each 24-hour exposure period, it was considered appropriate to base the results on geometric mean measured concentrations. These were calculated to be 0.0029, 0.0068, 0.011, 0.017 and 0.036 mg/L.

The mean hatching success of embryos in the control and solvent control groups group was 100% and 99%, respectively, which was in excess of the validity criterion of ≥70%. The mean post-hatch survival in the control and solvent control groups was 81% and 82%, respectively, which was in excess of the validity criterion of ≥75%. The test is therefore considered to be valid.

No statistically significant differences were observed in terms of hatching success, post-hatch survival, final fish lengths and final fish wet weights at any of the test concentrations employed in the test up to the test substance’s functional water solubility limit compared to the combined controls. In addition, no dose related effects were observed in terms of the number of normal larvae observed at hatch.

The limit of quantification (LOQ) was 0.0003 mg/L. Analysis of the freshly prepared media at a nominal concentration of 0.50 mg/L showed measured concentrations to range from 67% to 107% of nominal throughout the duration of the test. These results indicated that the test organisms were initially exposed to concentrations close to nominal at each media renewal.

Analysis of the 4-hour old media on Day 0 (test start) showed a measured concentration of 68% of nominal for the 0.50 mg/L test concentration. This decreased to 33% of nominal after the first 24 hours of exposure (Day 1). On Day 0 post-hatch, the measured concentration in the 4-hour old media sample was 36% of nominal which decreased to less than the LOQ after 24-hours (Day 1 post-hatch). For the remainder of the test the 4-hour old sample results ranged from 8% to 24% of nominal with the 24-hour old samples generally less than the LOQ. These results showed the test substance was unstable in the test media but may also interact with biological material as the decrease in measured concentration over the 4- and 24hour periods increased as the organisms hatched and grew.

A similar trend in analytical measurements was observed for the remaining test concentrations. Due to the decrease in measured concentration over each 24-hour exposure period, it was considered appropriate to base the results on geometric mean measured concentrations. These were calculated to be 0.0029, 0.0068, 0.011, 0.017 and 0.036 mg/L.

Reported statistics and error estimates:

Statistical analysis of the data was performed using the CETIS program v 1.8.6.8.
The hatching success results from the control and solvent control groups were compared using the Unequal Variance t Two-Sample test. The post-hatch survival, lengths and wet weight results were compared using the Equal Variance t TwoSample test. Based on this analysis, the results for the test concentrations were compared to the combined controls.

To determine the NOEC and LOEC, the number of hatched larvae were compared to the combined controls using the Dunn/Bonferroni-Holm Test. The number of larvae surviving at 28 days post-hatch and Day 28 lengths and wet weights for the test concentrations were compared to the combined controls using the Dunnett Multiple Comparison Test.

The NOEC and LOEC values for percentage normal larvae at hatch were not statistically derived given that only four abnormal larvae were observed at hatch and no concentration dependent response was observed.

No statistically significant differences were observed between the control and solvent control groups in terms of hatching success, post-hatch survival or growth (total lengths and wet weights). The results from the treatment groups were therefore compared to the combined control groups.

First egg hatch occurred between Day 2 and 4 and completion of hatching occurred between Days 4 and 6 (post-egg addition) in all treatment and the control vessels. NOEC and LOEC values for time to first egg hatch and the egg-hatching period were therefore not statistically derived. This indicated no difference in the time to first hatch or hatching period across all treatments when compared to the control and solvent control groups.

The mean hatching success of embryos in the control and solvent control vessels were 100% and 99%, respectively, which was in excess of the validity criterion of ≥70%. It was therefore considered that the validation criterion had been achieved. 

Mean hatching success in the treatments ranged between 80% - 90%. There were no statistically significant effects on hatching success at any of the test concentrations employed in the test compared to the combined controls.

Table 1 - Hatching success

Nominal concentration (mg/L)	Geometric Mean Measured Concentration (mg/L)	Hatching success (%)
Control	Control	100
Solvent control	Solvent control	99
0.031	0.0029	85
0.063	0.0068	80
0.13	0.011	84
0.25	0.017	83
0.50	0.036	90

On Day 0 post-hatch, two larvae in the solvent control and a single larvae in the 0.031 and 0.50 mg/L test concentrations were observed to have a bent spine. No further abnormalities were observed in the newly hatched larvae. NOEC and LOEC values for percentage normal larvae at hatch were therefore not statistically derived. This indicated no difference in the percentage normal larvae at hatch across all treatments when compared to the control and solvent control groups.

Table 2 - Normal Larvae at Hatch

Nominal concentration (mg/L)	Geometric Mean Measured Concentration (mg/L)	Normal larvae at hatch (%)
Control	Control	100
Solvent control	Solvent control	97
0.031	0.0029	99
0.063	0.0068	100
0.13	0.011	100
0.25	0.017	100
0.50	0.036	99

The mean post-hatch survival in the control and solvent control groups was 81% and 82%, respectively, which satisfied the validity criterion of ≥75%. It was therefore considered that the validation criterion had been achieved.

Mean post-hatch survival in the treatments ranged between 76% - 89%. There were no statistically significant effects on post-hatch survival at any of the test concentrations used compared to the combined control.

Table 3 - The Survival of Hatched Larvae at Day 28 post-hatch

Nominal concentration (mg/L)	Geometric mean measured concentration (mg/L)	Post-hatch survival Day 28 (%)
Control	Control	81
Solvent control	Solvent control	82
0.031	0.0029	76
0.063	0.0068	83
0.13	0.011	79
0.25	0.017	89
0.50	0.036	83

 

There were no statistically significant effects on fish length or wet weight at any of the test concentrations employed in the test compared to the combined controls.

Table 4 - Total Length (mm) and Wet Weight (mg) Measurements

Nominal concentration (mg/L)	Geometric mean measured concentration (mg/L)	Mean total length (mm)	Mean wet weight (mg)
Control	Control	21.6	79.0
Solvent control	Solvent control	22.1	98.8
0.031	0.0029	22.9	109.6
0.063	0.0068	22.3	102.8
0.13	0.011	23.1	109.2
0.25	0.017	22.0	91.4
0.50	0.036	22.0	93.7

A small number of fish were observed to be either small, pale, to have a bent spine, to be swimming abnormally or to be small with a bent spine (see Appendix 5). However, these observations were not concentration specific and were therefore not considered to be due to any toxic effect but rather natural variation within the population. 

Validity criteria fulfilled:

yes

Conclusions:

In a long-term toxicity to fish study, conducted according to OECD Test Guideline 210 and in compliance with GLP, a NOEC and LOEC for hatching success, normal larvae at hatch, posthatch survival and growth were concluded to be 0.5 mg/L and >0.50 mg/L, respectively, based on nominal concentrations. The NOEC and LOEC for hatching success, normal larvae at hatch, posthatch survival and growth were concluded to be 0.036 mg/L and >0.036 mg/L respectively, based on geometric mean measured concentrations.

Cross-reference 2

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-11-30 to 2018-03-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Version / remarks:

2012

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

liquid

Analytical monitoring:

yes

Remarks:

measured the parent substance

Details on sampling:

- Concentrations: (nominal) control, solvent control, 0.0313, 0.0625, 0.125, 0.250, 0.500 mg/L
- Sampling method: LC-MS/MS once within every 7 days in fresh media at the start of an exposure interval (0 hours) and in old media at the end of an exposure interval (24 hours).
- Sample storage conditions before analysis: Samples were analysed immediately (as far as technically possible) following sampling, All original samples were stored at room temperature. Prepared samples were stored at room temperature in an autosampler until analysis.

Vehicle:

yes

Remarks:

Solvent used: dimethylformamide, a solvent control was used

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Stock solutions were freshly prepared for each exposure interval and each concentration level. The stock solutions were prepared by direct addition of the appropriate amount of test item by pipette (the relative density of the test item of 0.877 was taken into account) into DMF. The concentrations of the stock solutions were as follows: 0.625 - 1.25 - 2.50 - 5.00 - 10.0 g/L
- Eluate: not reported
- Differential loading: not reported
- Controls: control and solvent control
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): dimethylformamide (DMF) was prepared and tested under the same conditions as the test item concentrations and the control.
- Concentration of vehicle in test medium (stock solution and final test solution(s) or suspension(s) including control(s)): 0.05 mL/L in every test concentration and solvent control, 0 ml/L in control
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): The test item solutions were mixed thoroughly by manual agitation, no reported evidence of undissolved material
- Other relevant information:

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Strain/clone: STRAUS Clone 5
- Justification for species other than prescribed by test guideline: N/a
- Age at study initiation (mean and range, SD): Less than 24 hours old daphnids from a healthy stock were used for the study. Juvenile daphnids were removed from the culture vessels at the latest 24 hours before the start of the exposure and discarded. The juveniles born within this period of max. 24 hours preceding the exposure were used for the test. No first brood progeny was used for the test.
- Weight at study initiation (mean and range, SD): not reported
- Length at study initiation (length definition, mean, range and SD): not reported
- Stage and instar at study initiation: not reported
- Valve height at study initiation, for shell deposition study (mean and range, SD): N/a
- Peripheral shell growth removed prior to test initiation: N/a
- Method of breeding: In glass vessels (2 - 3 L capacity) with approximately 1.8 L culture medium, at 20  2 °C, in an incubator, 16 hours illumination; light intensity of max. 1500 lx
- Source: Institut Dr. Nowak, Mayenbrook 1, 28870 Ottersberg, Germany
- Age of parental stock (mean and range, SD): not reported
- Feeding during test - yes
- Food type: Pseudokirchneriella subcapitata and Desmodesmus subspicatus suspension was provided as food corresponding to 0.2 mg C per daphnid and day.
- Amount: 0.2 mg C per daphnid and day.
- Frequency: Daily feeding per test vessel

ACCLIMATION
- Acclimation period: Acclimatization was not necessary, because the composition of the dilution water used for test medium preparation was equivalent to the culture medium.
- Acclimation conditions (same as test or not): N/a
- Type and amount of food: N/a
- Feeding frequency: N/a
- Health during acclimation (any mortality observed): N/a

QUARANTINE (wild caught)
- Duration: N/a
- Health/mortality: N/a

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES, INCLUDING CULTURING CONDITIONS: N/a

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Remarks on exposure duration:

none

Post exposure observation period:

none

Hardness:

as CaCO3.
In control group: 216-257.
In solvent control: 224-280
In test concentrations 0.199 and 0.562: 225-260

Test temperature:

In control group: 20.1-20.7
In solvent control: 19.7-20.7
In test concentrations 0.199 and 0.562: 19.7-20.6

pH:

In control group: 7.05-7.47
In solvent control: 7.30-7.44
In test concentrations 0.199 and 0.562: 7.31-7.45

Dissolved oxygen:

In control group: 6.66-9.19
In solvent control: 7.49-9.56
In test concentrations 0.199 and 0.562: 7.95-9.18

Salinity:

Not reported

Conductivity:

Not reported

Nominal and measured concentrations:

Nominal: 0.0313, 0.0625, 0.125, 0.250, 0.500 mg/L
Measured: 0.025, 0.043, 0.103, 0.199, 0.562 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Sealed glass flasks (4.5 (ID) x 9.5 (H) cm) with screw caps were used and filled up to the top with the test solutions. A test volume of approximately 130 mL was provided in each test vessel.
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: (4.5 (ID) x 9.5 (H) cm) with screw caps were used and filled up to the top with the test solutions. A test volume of approximately 130 mL was provided in each test vessel.
- Aeration: Test vessels were not aerated during the test.
- Type of flow-through (e.g. peristaltic or proportional diluter): semi-static test so N/a
- Renewal rate of test solution (frequency/flow rate): The test solutions were renewed daily. For this purpose, a second set of test vessels was filled with the freshly prepared test solutions and the daphnids were transferred by pipette
- No. of organisms per vessel: 10 daphnids
- No. of vessels per concentration (replicates): 10 replicates for all concentrations
- No. of vessels per control (replicates): 10
- No. of vessels per vehicle control (replicates): 10
- Biomass loading rate:N/a

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:Same composition as the culture medium (culture medium Elendt M4)
- Total organic carbon: Not reported
- Particulate matter: not reported
- Metals: as standard in Elendt M4 culture medium (OECD 202 Annex 3)
- Pesticides: not reported
- Chlorine: as standard in Elendt M4 culture medium (OECD 202 Annex 3)
- Alkalinity: as standard in Elendt M4 culture medium (OECD 202 Annex 3)
- Ca/mg ratio: as standard in Elendt M4 culture medium (OECD 202 Annex 3)
- Conductivity: not reported
- Culture medium different from test medium: no
- Intervals of water quality measurement: once every seven days in fresh media and at the end of an exposure interval (24h)

OTHER TEST CONDITIONS
- Adjustment of pH: adjusted to pH 7.0-7.5
- Photoperiod: 16/8 hours light/dark cycle
- Light intensity: Max. 1500 lx

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : mortality of parental daphnids (once a day at least), neonates (checked daily), condition of parental daphnids (daily), total body length/mean dry weight of parental daphnids (at the end of the test), first time to brood, intrinsic rate of population increase, number and size of first brood per animal

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 0.0313 - 0.0625 - 0.125 - 0.250 - 0.500 mg/L
- Justification for using less concentrations than requested by guideline: N/a
- Range finding study
- Test concentrations: n/a
- Results used to determine the conditions for the definitive study: n/a

Reference substance (positive control):

yes

Remarks:

Test is undertaken once a month at the test facility

Key result

Duration:

21 d

Dose descriptor:

EC10

Effect conc.:

> 0.189 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

(C.I 0.119-0.300)

Key result

Duration:

21 d

Dose descriptor:

EC10

Effect conc.:

> 0.25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 0.199 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

and adult mortality

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 0.25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

and adult mortality

Details on results:

- Behavioural abnormalities: None observed
- Observations on body length and weight: mean length of survived parents for control, solvent control, 0.025, 0.043, 0.103, 0.199, 0.562 mg/L : 4.63, 4.63, 4.70, 4.63, 4.58, 4.50mm and N/a as mortality was 100% in the 0.562 treatment.
- Other biological observations: In the geometric mean measured concentration level of 0.199 mg/L, one parental daphnid was identified as a male during the exposure period. This parental daphnid was treated as accidental mortality and was not taken into account for any further evaluation. No stillborn juveniles or aborted eggs were observed in the control or solvent control during the exposure period of 21 days. In the geometric mean measured concentrations levels of 0.025 mg/L and 0.043 mg/L, a total of 1 and 47 stillborn juveniles were observed, respectively. First appearance of living juveniles mean day for all treatments and controls = day 9 (except for 0.562 mg/L as 100% mortality of parents occurred). No ephippia were observed in the control or in the test groups during the test.
- Mortality of control: 0% mortality in the solvent control and the control
- Other adverse effects control: no adverse effects observed in the control or solvent control
- Immobilisation of control: 0%
- Abnormal responses: described in 'Other biological observations'
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: The measured test item concentration in fresh media at the start of the respective exposure intervals (0 hours) were in the range of 101 to 296% of the nominal concentrations and 16 to 100% in old media at the end of the respective exposure intervals (48 hours). The exact reasons for the determined outliers > 126% are unknown. Possible factors of influence may be the tested concentrations near the functional water solubility of the test item and recoveries near the LOQ of the analytical method. Further, the test item is not stable under test conditions and degradation products may influence recovery rates.
- Effect concentrations exceeding solubility of substance in test medium: no - solvent used

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: EC50 = 1.66 mg/L of potassium dichromate (C.I. <1.00-4.00)
- Other: The percentage of immobility for the reference item potassium dichromate (SIGMA-ALDRICH, batch number MKBV0900V, purity 99.0%, CAS RN 7778-50-9) was determined after 24 hours from 2018-03-13 to 2018-03-14.

Reported statistics and error estimates:

Reproduction NOEC/LOEC based on geometric mean concentrations:
Shapiro Wilk's Test on normal distribution: Number of residuals = 55; Shapiro-Wilk´s W = 0.782; p(W) = <0.001; p(W) is smaller than or equal to the selected significance level of 0.010; therefore, treatment data significantly differ from normal distribution.
Levene's Test on Variance Homogeneity: The Levene test indicates variance heterogeneity (p <= 0.010). Variance homogeneity check failed. Also the degree of normal distribution is poor. Therefore, the mediantest (2-by-2 table) with Bonferroni correction is performed.
Multiple Sequentially-rejective Median (2x2-Table) Test After Bonferroni-Holm: A NOEC of 0.1990 mg/L is suggested by the program.

Table 1 – Effects on adult mortality and reproduction for all introduced and for surviving parents (based on the geometric mean measured concentrations of the test item Triethoxyoctylsilane)

Geometric mean measured test item concentration (mg/L)	Adult mortality (%)	Mean number of offspring per introduced parental daphnid - Mean	Mean number of offspring per introduced parental daphnid - SD	Mean number of offspring per introduced parental daphnid - CV	Mean number of offspring per survived parental daphnid – mean	Mean number of offspring per survived parental daphnid – SD	Mean number of offspring per survived parental daphnid – CV
0.562	100	n.a.^1	n.a.^1	n.a.^1	n/a – 100% mortality^1	n/a – 100% mortality^1	n/a – 100% mortality^1
0.199^2	11.1	126	53.7	42.7	142	27.4	19.3
0.103	10	144	51.4	35.8	159	16.1	10.1
0.043	20	154	14.1	9.2	158	12.1	7.6
0.025	0	159	11.3	7.1	159	11.3	7.1
Solvent control	0	131	22.3	17.1	131	22.3	17.1
Control	0	144	21.2	14.7	144	21.2	14.7

¹statistically significant reduction of the reproductive output, compared to pooled controls

²one parental daphnid was identified as male and that replicate was excluded from evaluation

n.a. not applicable, since no juveniles were observed

 

Table 2 – Mortality (%) of the adult Daphnids after 7, 14 and 21 days of exposure (n=10)

Geometric mean measured test item concentration (mg/L)	Adult mortality – 7 days	Adult mortality – 14 days	Adult mortality – 21 days
0.562	100^1	100^1	100^1
0.199^2	11.1	11.1	11.1
0.103	0	10	10
0.043	0	0	20
0.025	0	0	0
Solvent control	0	0	0
Control	0	0	0

¹statistically significant compared

²one parental daphnid was identified as male and that replicate was excluded from evaluation (n=9)

 

Table 3 – Intrinsic Rates of Natural Increase

Geometric mean measured test item concentration (mg/L)	Intrinsic rate of natural increase in replicate no 1	Intrinsic rate of natural increase in replicate no 2	Intrinsic rate of natural increase in replicate no 3	Intrinsic rate of natural increase in replicate no 4	Intrinsic rate of natural increase in replicate no 5	Intrinsic rate of natural increase in replicate no 6	Intrinsic rate of natural increase in replicate no 7	Intrinsic rate of natural increase in replicate no 8	Intrinsic rate of natural increase in replicate no 9	Intrinsic rate of natural increase in replicate no 10	Mean IR MV± SD	CV (%)
0.562	-	-	-	-	-	-	-	-	-	-	-	-
0.199	0.404	0.256	0.405	0.450	-	0.300	0.373	*	0.432	0.300	0.378 ± 0.0563	14.9
0.103	0.396	0.379	0.417	0.406	0.413	0.384	0.361	0.435	0.378	-	0.397 ± 0.0231	5.8
0.043	0.389	0.399	0.386	0.389	-	0.427	0.409	0.393	0.384	-	0.397 ± 0.0145	3.6
0.025	0.407	0.401	0.572	0.390	0.448	0.378	0.397	0.400	0.398	0.372	0.416 ± 0.0585	14.0
Solvent Control	0.379	0.385	0.390	0.410	0.386	0.360	0.406	0.383	0.362	0.341	0.380 ± 0.0209	5.5
Control	0.384	0.41	0.381	0.359	0.363	0.388	0.384	0.390	0.346	0.408	0.381 ± 0.0203	5.3

- Not applicable, due to the mortality of the parental daphnid(s)

* parental daphnid was identified as male and that replicate was excluded from evaluation

Table 4 – First Appearance of Living Juveniles at the Introduced Parental Daphnids in the Individual Groups:

Geometric mean measured test item concentration (mg/L)	Day of first appearance of living juveniles at the survived parental daphnids in replicate no 1	Day of first appearance of living juveniles at the survived parental daphnids in replicate no 2	Day of first appearance of living juveniles at the survived parental daphnids in replicate no 3	Day of first appearance of living juveniles at the survived parental daphnids in replicate no 4	Day of first appearance of living juveniles at the survived parental daphnids in replicate no 5	Day of first appearance of living juveniles at the survived parental daphnids in replicate no 6	Day of first appearance of living juveniles at the survived parental daphnids in replicate no 7	Day of first appearance of living juveniles at the survived parental daphnids in replicate no 8	Day of first appearance of living juveniles at the survived parental daphnids in replicate no 9	Day of first appearance of living juveniles at the survived parental daphnids in replicate no 10	First appearance mean day
0.562	-	-	-	-	-	-	-	-	-	-	-
0.199	9	8	9	8	-	10	8	-*	9	9	9
0.103	9	8	9	9	9	10	9	8	9	8	9
0.043	9	9	9	10	9	9	9	10	8	10	9
0.025	9	9	8	9	8	9	9	9	9	9	9
Solvent Control	9	9	9	9	9	9	9	9	8	9	9
Control	9	9	9	10	9	9	9	9	10	9	9

- no juveniles occurred

* parental daphnid was identified as male and that replicate was excluded from evaluation

 

Table 5 – Total Body Length and Dry Weight of the Survived Parental Daphnids

Geometric mean measured test item concentration (mg/L)	Total length of the survived parent animals (mm). Replicate no 1	Total length of the survived parent animals (mm). Replicate no 2	Total length of the survived parent animals (mm). Replicate no 3	Total length of the survived parent animals (mm). Replicate no 4	Total length of the survived parent animals (mm). Replicate no 5	Total length of the survived parent animals (mm). Replicate no 6	Total length of the survived parent animals (mm). Replicate no 7	Total length of the survived parent animals (mm). Replicate no 8	Total length of the survived parent animals (mm). Replicate no 9	Total length of the survived parent animals (mm). Replicate no 10	MV (mm)	N	Dry weight (mg) – sum	Dry weight (mg) - MV
0.562	-	-	-	-	-	-	-	-	-	-	-	0	-	-
0.199	4.25	4.75	4.5	4.5	-	4.5	4.5	2.5*	4.5	4.5	4.5	8	7.0	0.875
0.103	4.5	4.75	4.75	4.5	4.5	4.75	4.25	4.5	4.75	-	4.58	9	8.6	0.956
0.043	4.5	4.5	4.5	4.75	-	5.0	4.5	4.75	4.5	-	4.63	8	7.4	0.925
0.025	4.75	4.75	4.5	5.0	4.75	4.5	4.75	4.75	5.0	4.25	4.7	10	8.2	0.820
Solvent Control	4.75	4.5	4.5	5.0	5.0	4.5	4.5	4.5	4.5	4.5	4.63	10	8.7	0.870
Control	4.5	4.75	4.5.2	4.75	4.5	4.5	4.75	4.5	5.0	4.5	4.63	10	8.2	0.820

N number of the survived parental daphnid

- not applicable, due to the mortality of the parental daphnid(s)

* parental daphnid was identified as male and excluded from evaluation

Table 6 – Measured Concentrations of the Test Item during the Definitive Test

Sampling day       Nominal test item conc. (mg/L)	Day 0 - Start of the exposure interval (0 hours) - Meas. Conc. (mg/L)	Day 0 - Start of the exposure interval (0 hours) - %	Day 1 – End of the Exposure interval (24 hours) - Meas. Conc. (mg/L)	Day 1 – End of the Exposure interval (24 hours) - %	Day 7 – Start of the exposure interval (0 hours) - Meas. Conc. (mg/L)	Day 7 – End of the exposure interval (0 hours) - Meas. conc. (mg/L)	Day 8 – Start of the exposure interval (24 hours) - Meas. Conc. (mg/L)	Day 8 – End of the exposure interval (24 hours) - Meas. conc. (mg/L)
0.500	1.41	283	0.224	45	n.d.	n.d.	n.d.	n.d.
0.250	0.301	120	0.130	52	0.287	115	0.140	56
0.125	0.152	121	0.0736	59	0.127	101	0.0653	52
0.0625	0.0706	113	0.0101	16	0.0946	151	0.0297	48
0.0313	0.0354	113	0.0312	100	0.0317	101	0.00824	26
Control	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ
Solvent control	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ

 

Sampling day	Day 14 – Start of the exposure interval (0 hours) - Meas. Conc. (mg/L)	Day 7 – End of the exposure interval (0 hours) - %	Day 15 – Start of the exposure interval (24 hours) - Meas. Conc. (mg/L)	Day 15 – End of the exposure interval (24 hours) - %	Geometric mean measured (mg/L)
0.500	n.d.	n.d.	n.d.	n.d.	0.562
0.250	0.340	136	0.116	46	0.199
0.125	0.146	117	0.0882	71	0.103
0.0625	0.107	171	0.0279	45	0.0426
0.0313	0.0928	296	0.00851	27	0.0247
Control	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ
Solvent control	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ

Meas. conc. Measured concentration of the test item, dilution factor taken into account

% percent of the nomnal concentration of the test item

LOQ limit of quantification of the analytical method (30.0 µg test item/L)

n.d. not determined

Validity criteria fulfilled:

yes

Conclusions:

A 21-day reproduction NOEC of ≥0.199 mg/L and EC10 value of >0.189 mg/l (geometric mean measured concentrations) have been determined for the effects of the test substance on reproduction of Daphnia magna. A 21-day adult mortality NOEC of ≥0.199 mg/L (geometric mean measured concentration) has been determined for the effects of the test substance on mortality of Daphnia magna. It is likely that the test organisms were primarily exposed to the parent substance.

Cross-reference 3

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-03-31 to 2008-04-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Sampling method: At test initiation and at 24 hours of exposure, one sample was removed from the test solution and each control and analysed for triethoxy(octyl)silane. Samples analysed on day 0 were removed from the test solutions in the volumetric flasks prior to inoculation with algae and filling the individual replicate test flasks. Samples analysed at 24 hours of exposure were removed from the approximate midpoint of the test vessel and composited. Since the 24-hour measured concentrations were below the limit of quantitation, no additional analytical samples were collected or analysed.

- Sample storage conditions before analysis: The extraction solvent, iso-octane, was immediately added to each analytical sample which stopped hydrolysis of the test substance.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A 1.3 mg a.i./ml stock solution was prepared prior to test initiation by placing 0.0328 g of triethoxy(octyl)silane (0.0325 g as active ingredient) in a 25-ml volumetric flask and bringing it to volume with dimethylformamide (DMF, CAS No. 68-12-2). The resulting stock solution was observed to be clear and colourless with no visible undissolved test substance. Duplicate 0.13 mg a.i./l test solutions were prepared by bringing 0.10 ml of the 1.3 mg a.i./ml primary stock solution to a final volume of 1000 ml with AAP medium. Due to the known rapid hydrolysis of the test substance, the test solutions were prepared in individual volumetric flasks and mixed for approximately one minute.

- Controls: Dilution water control and Dilution water + solvent (DMF; 0.1 ml/l) control.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM

- Source (laboratory, culture collection): The alga was obtained from University of Texas, Austin, Texas, and was maintained in stock culture at Springborn Smithers.

- Culture medium: The culture medium used was Algal Assay Procedure (AAP) medium prepared with sterile, deionized water.

- Stock culture: Stock cultures were grown in 250-ml glass flasks each containing 100 mL of medium. The flasks were covered with stainless steel caps which permitted gas exchange. The stock cultures were maintained within the following conditions: a shaking rate of 100 ± 10 rpm, a temperature of 23 ± 1 ºC and continuous illumination at the surface of the medium with an intensity range of 4400 to 5900 lux (420 to 550 footcandles). Lighting was supplied by Premira VitaLux® fluorescent bulbs. Culture flasks were agitated continuously on an orbital shaker. Temperature was controlled using an environmental chamber. The inoculum used to initiate the toxicity test with triethoxy(octyl)silane was taken from a stock culture that had been transferred to fresh medium three days before testing.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Hardness:

Conductivity: 80 μmhos/cm

Test temperature:

24ºC

pH:

7.2 - 7.3 at start of test

8.6 - 9.2 at end of test

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (Control), 0 (Solvent control) and 0.13 mg/l. The nominal concentration of 0.13 mg/l was based on the results of a preliminary study of the solubility of the substance.

At 0 hour, the measured concentration of triethoxy(octyl)silane in the test solution, 0.11 mg a.i./l, closely approximated the desired nominal concentration. The concentration of triethoxy(octyl)silane decreased to below detectable limits (<0.020 mg a.i./l) at 24 hours of exposure. The test substance is known to rapidly hydrolyse in water (e.g., at pH 7.0 the half-life time has been determined to between 0.3 and 0.6 hours at 25 ºC).

Details on test conditions:

TEST SYSTEM

- Test vessel: Replicate 250-ml flasks, three for the control and six for the treatment level and solvent control, were conditioned prior to use by rinsing with the appropriate test solution. One hundred milliliters of the appropriate test solution was then placed in each replicate flask. Each test flask was labelled with the test concentration, replicate, test species and study number. All test vessels were fitted with stainless steel caps which permitted gas exchange.

- Inoculation of test vessels: Each flask was provided with the required cell density of approximately 1.0 x 10E4 cells/ml.

- Culture medium: Algal Assay Procedure (AAP) medium (Miller et al., 1978) used to prepare the exposure solutions. The initial pH of this medium was adjusted, if necessary, to 7.5 ± 0.1 prior to use.

- Test conditions: The test was conducted in an environmental chamber designed to maintain the test conditions: a temperature of 23 ± 2 ºC, continuous light intensity of 4400 to 5900 lux (420 to 550 footcandles) and photosynthetically-active radiation (PAR) range of 60 to 120 μE/m2/s. An orbital shaker table provided a shaking rate of 100 ± 10 rpm. Following each observation interval, the test flasks were assigned new random positions based on computer-generated random numbers.

- Water quality: Water quality parameters (pH and conductivity) were measured at test initiation and at the termination of the 72-hour exposure period. Test solution pH was measured with a Jenco Model 60 pH meter, and conductivity was measured with a Yellow Springs Instrument (YSI) Model No. 33 salinity-conductivity-temperature meter.

_ Selection of test concentrations: Based on the reported solubility of the test substance (< 0.13 mg/l) and in consultation with the Study Sponsor, nominal concentrations of 0 (control and solvent control) and 0.13 mg a.i./l were selected for the definitive limit test.

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 0.13 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 0.13 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 0.13 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

biomass

Remarks:

(expressed as yield)

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 0.13 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

biomass

Remarks:

(expressed as yield)

Details on results:

- Exponential growth in the control (for algal test): yes

Reported statistics and error estimates:

Since this test was conducted as a 72-hour limit test (one concentration) and the concentration tested did not produce > 10% inhibition in yield, growth rate or biomass, the ECx values were empirically estimated to be greater than the nominal concentration tested.

Table 1. Results of analysis of test media

 

Nominal concentration (mg/l)	Measured concentration at start of test (mg/l)	Measured concentration after 24 hours (mg/l)
0 (Control)	<0.020	<0.020
0 (Solvent control)	<0.020	<0.020
0.13	0.11/0.11*	<0.020/<0.020*

*Analysis performed of media that did not contain algae

 

Table 2. Test results

 

Nominal concentration (mg/l)	Measured cell density at start of test (cells/ml)	Measured cell density after 24 hours (cells/ml)	Measured cell density after 48 hours (cells/ml)	Measured cell density after 72 hours (cells/ml)	Inhibition of growth rate (%)**	Inhibition of biomass (%)**
0 (Control)	10000	69200	380000	1900000	Not applic.	Not applic.
0 (Solvent control)	10000	63800	348000	1770000	-	-
0.13	10000	62900	400000	2020000	-2	-14**

**Compared with solvent control. A negative value indicates that growth was higher than in the Controls

Validity criteria fulfilled:

yes

Conclusions:

A 72-hour EC50 value of >0.13 mg/l and NOEC of ≥0.13 mg/l have been determined for the effects of the test substance on growth rate of Pseudokirchnerella subcapitata. The results are expressed relative to nominal test substance concentration because measured concentrations had declined to below the limit of quantification after 24 hours. The test substance is subject to hydrolysis and it is therefore likely that, under the static test conditions, the test organisms were exposed to the hydrolysis products of the substance.

Cross-reference 4

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

hydrolysis

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

See attached QMRFs/QPRFs

Principles of method if other than guideline:

The result was obtained using an appropriate QSAR method (see attached QMRF and QPRF for details)

The model for hydrolysis at pH 7 has been developed for, and applies specifically to di- and tri-alkoxysilanes. It is a multiple linear regression based model with descriptors representing (i) steric effects of the alkoxy group, (ii) steric effects of the side-chain(s), and (iii) electronic effects of the side-chain(s).

The models for hydrolysis at pH 4, 5 and 9 have been developed for, and apply specifically to organosilicon compounds. They are linear regression based models where the descriptor is the half-life at pH 7.

Transformation products:

yes

No.:

#1

No.:

#2

Key result

pH:

4

DT50:

0.7 h

Remarks on result:

other: 20-25°C

Key result

pH:

5

DT50:

0.7 h

Remarks on result:

other: 20-25°C

Key result

pH:

7

DT50:

30 h

Remarks on result:

other: 20-25°C

Key result

pH:

9

DT50:

0.4 h

Remarks on result:

other: 20-25°C

Conclusions:

Hydrolysis half-life values at 20-25°C of 0.7 h at pH 4, 30 h at pH 7 and 0.4 h at pH 9 were obtained using an accepted calculation method. The result is considered to be reliable.

Materials and methods

Test material

Test material information

Constituent 1

Reference substance name:

Triethoxyoctylsilane

EC Number:

220-941-2

EC Name:

Triethoxyoctylsilane

Cas Number:

2943-75-1

Molecular formula:

C14H32O3Si

IUPAC Name:

triethoxy(octyl)silane