Amino functional alkoxysilanes

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

19th of September 2019 to 15th of January 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1300 (Daphnid Chronic Toxicity Test)

Version / remarks:

1996

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Version / remarks:

2012

Deviations:

yes

Remarks:

Only one concentration used (rather than five)

GLP compliance:

yes (incl. QA statement)

Remarks:

In total, three exceptions are listed, however, these are not expected to have provided any impact on the quality of the study.

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0 (water control) and 12 mg methylsilanetriol/L
- Sampling method: The bulk water control and bulk test solution were sampled at test initiation (day 0) and on days 2, 7, 14 and 19 of the exposure. Spent (pooled replicate) solutions were sampled on days 2, 5, 7 and 14 as well as at exposure termination (day 21). To assess analytical method precision and solution homogeneity, three additional samples were collected on day 0, 7, 14 and 19 from the bulk test solution. The collected samples were analysed for methylsilanetriol by HPLC/MS-MS. Validation of the analytical methodology was conducted concurrently with the study as per standard operating procedure (SOP) MTH-ACL-2 (2014).
- Sample storage conditions before analysis: Not reported.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The definitive test was conducted under static-renewal conditions for 21 days. Ten replicate test vessels, each containing test solution or LDW were prepared per test level. At test initiation, one daphnid was impartially added to each test vessel within 30 minutes of the addition of the test solutions. The replicate test vessels were placed into a temperature-controlled environmental chamber according to a computer-generated randomization.
- Eluate: not specified
- Differential loading: not specified
- Controls: water
- Chemical name of vehicle: n/a
- Concentration of vehicle in test medium: n/a
- Evidence of undissolved material: not specified

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Strain/clone: n/a
- Justification for species other than prescribed by test guideline: n/a
- Age at study initiation: Less than 24 hours
- Weight at study initiation: n/a:
- Length at study initiation: Mean length per surviving adult female were 4.81 mm in the water control and 4.85 mm in the 10.0 mg/L test level.
- Stage and instar at study initiation: n/a
- Valve height at study initiation, for shell deposition study: n/a
- Peripheral shell growth removed prior to test initiation: n/a
- Method of breeding: n/a
- Source: In house cultures obtained originally from Aquatic BioSystems, Inc., Fort Collins, Colorado
- Age of parental stock: n/a
- Feeding during test : Daphnids were fed with Raphidocelis subcapitata and YTC (yeast, wheat grass, finfish food suspension) daily from the test initiation (day 0) to day 20, however, not on day 21.
- Food type: Raphidocelis subcapitata and YTC (yeast, wheat grass, finfish food suspension)
- Amount: 0.8 mL Raphidocelis subcapitata and 0.1 mL YTC (yeast, wheat grass, finfish food suspension) daily between day 0-6. Thereafter, 0.9 ml of Raphidocelis subcapitata and 0.1 mL YTC between day 7-20. No food was provided on day 21. Therefore, the final feeding ration resulted in approximately 0.2 mg C/daphnid/day throughout the entire exposure period.
- Frequency: daily

ACCLIMATION
- Acclimation period: n/a
- Acclimation conditions: n/a
- Type and amount of food: n/a
- Feeding frequency: n/a
- Health during acclimation: not specified

QUARANTINE
- 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:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

21 d

Post exposure observation period:

n/a

Hardness:

58-62 mg CaCO3/L

Test temperature:

19–20°C

pH:

7.7-8.9

Dissolved oxygen:

8.0–10.5 mg/L (90–118% air saturation)

Salinity:

not specified

Conductivity:

160-170 µS/cm

Nominal and measured concentrations:

Nominal test concentration: 0 (water control) and 12 mg methylsilanetriol/L
Mean measured test concentrations: < LLQ (water control) and 10.0 mg methylsilanetriol/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 125-mL glass borosilicate jars containing approximately 90 mL of test solution. Each test vessel was loosely covered and uniquely labeled for identification purpose (i.e. replicate, study, test level). Test vessels were replaced with new/clean test vessels on renewal days.
- Type: closed
- Material/size/headspace/fill volume: Glass/125 ml/not specified/90 ml
- Aeration: not specified
- Type of flow-through: Septum Purge Flow (for the GC)
- Renewal rate of test solution (frequency/flow rate): 1 mL/min
- No. of organisms per vessel: 1 daphnia per vessel
- No. of vessels per concentration: 10
- No. of vessels per control: not specified
- No. of vessels per vehicle control: n/a
- Biomass loading rate: not specified

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The water was obtained from the upper Saginaw Bay of Lake Huron off Whitestone Point and was limed and flocculated with ferric chloride. Before use in the laboratory, the water was sand-filtered, pH-adjusted with gaseous CO2, carbon-filtered, and UV-irradiated.
- Total organic carbon: 1.9 mg/L,
- Particulate matter: < 2 mg/L
- Metals/pesticides/chlorine/alkalinity/Ca/mg ratio: concentrations of contaminants were below levels of concern that may have interfered with the results of this test.
- Conductivity: 160-170 μS/cm
- Culture medium different from test medium: No
- Intervals of water quality measurement: Weekly

OTHER TEST CONDITIONS
- Adjustment of pH: Yes, with gaseous CO2
- Photoperiod: 16 hours light/8 hours dark per day
- Light intensity: Not exceeding 1000-1500 lux.

EFFECT PARAMETERS MEASURED: not specified

TEST CONCENTRATIONS
- Spacing factor for test concentrations: not specified
- Justification for using less concentrations than requested by guideline: not specified
- Range finding study: No, based on available literature
- Test concentrations: 12 mg methylsilanetriol/L
- Results used to determine the conditions for the definitive study:

Reference substance (positive control):

no

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

LOEC

Remarks:

MATC

Effect conc.:

> 10 mg/L

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Conc. based on:

test mat.

Basis for effect:

growth

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

> 10 mg/L

Conc. based on:

test mat.

Basis for effect:

growth

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Conc. based on:

test mat.

Basis for effect:

other: mortality: Number of living offspring produced per surviving parental animal {for Daphnia magna, TG 211} (migrated information)

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

> 10 mg/L

Conc. based on:

test mat.

Basis for effect:

other: mortality: Number of living offspring produced per surviving parental animal {for Daphnia magna, TG 211} (migrated information)

Details on results:

- Behavioural abnormalities: No
- Observations on body length and weight: The daphnid lengths in the water control were not statistically different to the mean lenght per surviving adult female. No weight is recorded.
- Other biological observations: All biological data were normally distributed and homogenous.
- Mortality of control: 0 %
- Other adverse effects control: None reported
- Immobilisation of control: None reported
- Abnormal responses: None reported
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No
- Effect concentrations exceeding solubility of substance in test medium: No

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: Yes

Reported statistics and error estimates:

Shapiro-Wilk’s test at a Type I error rate of 0.01 was utilised for the testing of normality for reproduction and growth (length). To evaluate the homogeneity of variance, Levene's test at a type I error rate of 0.05 was used. Furthermore, a parametric analysis (ANOVA) was conducted using a Dunnett's test to compare the limit test level with the water control. one-tailed Dunnett’s test, looking for a significant decrease from the water control, was conducted at a Type I error rate of 0.05. Additionally, the standard deviation, coeffcient of variance and mean was calculated for e.g. the individual observations

Validity criteria fulfilled:

yes

Conclusions:

A 21 day NOEC value of 10 mg/l (highest concentration tested) has been determined for the effects of methylsilanetriol on reproduction, growth (length) and mortality of Daphnia magna. Additionally, LOEC for the same endpoints was determined to be >10 mg/L.

Executive summary:

A 21 day chronic toxicity study in Daphnia magna with the test substance methylsilanetriol (pre-hydrolysed from the parent substance methyltrimethoxysilane) was conducted according to OECD TG 211 and in compliance with GLP. A 21 day NOEC of 10 mg/l (highest concentration tested) was determined for the effects of methysilanetriol on reproduction, growth (length) and mortality. Additionally, a LOEC for the same endpoints was determined to be >10 mg/L.

Reference 3

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Guideline study with acceptable restrictions. The study was not conducted under GLP and exposure concentrations were not measured.

Qualifier:

no guideline followed

Principles of method if other than guideline:

The study consisted of triplicate runs of a 21-day test. Each run consisted of duplicates for control and all test concentrations. Each duplicate started with five 24-48 hour old Daphnia magna. Concentrations of 0.01, 0.03, 0. 1 , 0.3 and 1.0 ppm were selected for the test. First generation Daphnia mortality was recorded throughout the test and their reproductive function was assessed by counting the total number of young produced through day 21.

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The substance was added directly to 600 mL beakers, each containing 400 ml of hard reconstituted fresh water.

Test organisms (species):

Daphnia magna

Details on test organisms:

- Source: The test daphnids were from a laboratory culturing. The original colony of Daphnia magna was obtained through the Dow Chemical Company, which obtained their colony from the Duluth Laboratory of the United States Environmental Protection Agency.

- Culture medium: The colonies were maintained under static conditions in reconstituted hard water (EPA 660/3-75-009) made-up from glass-distilled water. Before culture inoculation, the reconstituted water was aerated for 2-4 hours.

- Culture conditions: The colonies were maintained in five-gallon glass aquaria under approximately 1000 foot-candle illumination (18/6 hour light/dark) in an environmental chamber designed to maintain 22+/-1°C.

- Feeding: The food for the Daphnia. magna is prepared each week by blending 0.25 g alfalfa meal, 4.0 g trout chow and 400 mL distilled water. This solution is allowed to settle and the supernatant is used as food.

- Test organisms; A number of egg-bearing daphnia were isolated prior to each test for a period of 24-48 hours. Five 24-48 hour old
Daphnia magna produced in the period prior to the test were introduced into each test concentration along with the untreated control group.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

No data

Test temperature:

22+/-1°C

pH:

No data

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (Control), 0.01, 0.03, 0.1, 0.3 and 1.0 ppm

Details on test conditions:

Five 24-48 hour old Daphnia magna were introduced into each test concentration along with the untreated control group.

The test consisted of triplicate runs of the 21-day test. Each run consisted of duplicates for control and all test concentrations, each duplicate started with five 24-48 hour old Daphnia magna.

The daphnia were fed 0.25 ml of daphnia food each day except weekends throughout the 21-day study.

Observations were made each day for each of the test concentrations and control groups for mortalities and young produced.

The daphnia were transferred to fresh test and control vessels weekly throughout the 2l-day study.

Survival of the first generation daphnids was recorded throughout the test. The reproductive function of the first generation daphnia was assessed by counting the total number of young produced through day 21.

Comparison between test vessels and controls were made for first generation survival, fecundity, and survival of the second generations. General observations of behaviour and abnormalities were also made.

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 other: ppm

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: reproduction and mortality

Details on results:

Control parental daphnia survival after 21 days: 96.7%

There were no statistically significant differences in survival and reproductive output between the Controls and any of the treatments.

Reported statistics and error estimates:

The levels of effect on survival and reproduction were insufficient to determine ECx values.

Differences in reproductive output were assessed by t test with p<0.05

Table 1. Test results

 

Nominal concentration (ppm)	Survival of parental daphnia (%)	Total young produced +/-Stand Dev	Young produced per female +/-Stand Dev	Initial survival of offspring (%)
0 (Control)	96.7	52.7+/-25.3	10.72+/-4.81	99.7
0.01	100	47.7+/-23.3	9.53+/-4.66	98.3
0.03	100	46.0+/-28.1	9.20+/-5.63	100
0.1	100	52.2+/-25.3	10.43+/-5.07	99.7
0.3	100	44.2+/-29.0	8.83+/-5.81	99.6
1.0	90	33.5+/-17.1	6.93+/-3.19	99.5

 

Validity criteria fulfilled:

yes

Conclusions:

A 21-day NOEC of ≥1 ppm has been determined for the effects of the test substance on survival and reproduction of Daphnia magna. The results are expressed relative to nominal concentrations of the test substance. However the substance is subject to rapid hydrolysis and under the test conditions it is therefore likely that exposure will have been to its hydrolysis products (methanol and trisilanols).

Description of key information

Silanol HP-X: 21-day NOEC ≥10 mg/l, effects of methylsilanetriol on mortality, reproduction and growth of Daphnia magna.

Silanol HP-Z: 21-day NOEC ≥1 mg/l, effects of {3-[(2-aminoethyl)amino]propyl}silanetriol on mortality and reproduction of Daphnia magna, read cross from N-(3-(Trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24 -3).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Remarks:

Silanol HP-X

Effect concentration:

> 10 mg/L

Fresh water invertebrates

Dose descriptor:

NOEC

Remarks:

Silanol HP-Z

Effect concentration:

> 1 mg/L

Additional information

The constituents of the substance hydrolyse rapidly, therefore the environmental aspects of chemical safety assessment are based on the hydrolysis products Silanol HP-W, HP-X, HP-Y and HP-Z. However, due to the uncertainty around hydrolysis rates of some of the constituents, the parent substance, divided into Blocks, is also assessed.

For assessment of the parent substance constituents, the data relevant to the corresponding silanol hydrolysis product are used.

A long-term Daphnia magna reproduction Siltest is available with methylsilanetriol, which is Silanol HP-X. A 21-day NOEC of ≥10 mg/l was determined for the effects of methylsilanetriol on mortality, reproduction and growth of Daphnia magna (Dow Chemical Company, 2019).

A long-term Daphnia magna reproduction test is available with N-(3-(Trimethoxysilyl)propyl)ethylenediamine, CAS 1760-24-3, which rapidly hydrolyses to {3-[(2-aminoethyl)amino]propyl}silanetriol, relevant to Silanol HP-Z. A 21-day NOEC of ≥1 mg/l was determined for the effects of {3-[(2-aminoethyl)amino]propyl}silanetriol on mortality and reproduction of Daphnia magna (Dow Corning, 1980).

Testing for long-term toxicity to invertebrates for Silanol HP-W and HP-Y is not considered necessary because:

The substance has acute toxicity data available for three trophic levels relevant for each constituent and for each silanol assessment entity, as well as chronic invertebrate and algal toxicity data for silanol assessment entities HP-X and HP-Z, which make up a large proportion of the whole substance.

 

For Silanols HP-W and HP-Y, no short-term toxicity of the test substance and degradation products to Daphnia was observed and the most sensitive species was algae. An assessment factor of 1000 was applied to derive the freshwater PNEC, this high assessment factor to derive the predicted no-effect level already reflects the typically higher value of a short-term EC₅₀ compared to a long-term EC₁₀. It is unlikely that the aquatic PNEC would be significantly over-estimated using this high assessment factor.

 

PNECs have been derived for the purpose of chemical safety assessment and the risk characterisation ratios for Silanols HP-W and HP-Y are below 1.

In addition, Silanols HP-Y and HP-W make up only a small proportion of the substance, therefore a large proportion of the substance is covered by the existing data. To achieve a concentration of silanols HP-Y and HP-W equivalent to the lowest effect concentration of 36 mg/l used to derive PNEC for Silanol HP-Y and HP-W, a loading of more than 100 mg/l of whole substance would be needed.

 

Please see the attached document in IUCLID Section 13, which gives details on structure and properties of the parent substance and its hydrolysis products, as well as the amount of each hydrolysis product produced per kg of parent substance.

All the silanol hydrolysis products are highly water-soluble and have low potential for bioaccumulation based on log K_ow <3.

Assessment of parent substance

The constituents of the parent substance have been divided into seven Blocks, A to G.

The approach of assessing only the hydrolysis product for constituents C-G is not supported based on uncertainty in the hydrolysis rates and current ECHA guidance. However, testing of this UVCB substance would be technically difficult and could not provide information useful for setting PNECs for the constituents. It is also unlikely to be possible to separate individual constituents for testing. In addition, there are no data available for read across to the parent substance.

For assessment of the parent substance, PNECs have therefore been derived for each Block using the data read across to the silanol hydrolysis products, but without molecular weight correction where applicable. The risk characterisation ratios derived using this approach are all <1.

 

Please refer to the discussion in IUCLID Section 6, Ecotoxicological Information, and CSR Section 7.0 for further information of the technical infeasibility of test the parent substance.

 

Overall it is concluded that the risk is adequately assessed using the short-term data and the long-term invertebrate tests, and that further testing is not considered necessary.

 

Details on how the PNEC and the risk characterisation ratio have been derived can be found in IUCLID Section 6.0 and Chapters 7, 9 and 10 of the Chemical Safety Report.