3-(trimethoxysilyl)propiononitrile

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Gene mutation (Bacterial reverse mutation assay / Ames test): negative with and without activation in all strains tested (similar to OECD TG 471) (Bushy Run Research Center, 1981).
Cytogenicity in mammalian cells: read-across from 3-(triethoxysilyl)propiononitrile (CAS 919-31-3): negative in Chinese hamster ovary K1 cells (OECD TG 473) (Bioreliance, 2004).
Mutagenicity to mammalian cells: negative with and without activation in L5178Y cells (OECD TG 476) (BSL Bioservice, 2011).

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1981-09-14 to 1981-09-19

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

other: BRRC Standard Operating Procedures 7.4.1. through 7.4.6 and 7.4.12

Version / remarks:

Ames test procedure

GLP compliance:

no

Type of assay:

bacterial reverse mutation assay

Target gene:

Histidine operon

Species / strain / cell type:

S. typhimurium, other: TA98, TA100, TA1535, TA1537, TA1538

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9

Test concentrations with justification for top dose:

0.1 µl/plate - 10 µl/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: ethanol

- Justification for choice of solvent/vehicle: None given in study report.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 4-Nitro-o-phenylenediamine 10 µg/plate

Remarks:

TA 98, TA 1538 (without activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

TA 100, TA 1535 (without activation): 10 µg/plate

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

Remarks:

TA 1537 (without activation): 60 µg/plate

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-Aminoanthracene 10 µg/plate

Remarks:

All strains (with activation)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION

- Expression time (cells in growth medium): 24 - 48 hours

NUMBER OF REPLICATIONS: 3 plates for each test concentration

DETERMINATION OF CYTOTOXICITY

- Method: relative total growth; background lawn assessment

Evaluation criteria:

The spontaneous reversion for the solvent controls must be within the laboratory's historical range. Positive controls must demonstrate that the test systems are responsive with known mutagens. A test chemical is considered a bacterial mutagen if the number of revertant colonies is at least twice the solvent control for at least one dose level and there is evidence of a dose-related increase in the number of revertant colonies.

Statistics:

No statistical information is included in the report.

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

3 µl/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

10 µl/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

10 µl/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

10 µl/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

10 µl/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

with

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

COMPARISON WITH HISTORICAL CONTROL DATA: Results were within range of historical control data

Table 2: Experiment 1 Plate incorporation - Number of revertants per plate (mean of 3 plates)

	TA98			TA100			TA1535
Conc. µl/plate	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	15	23	No	84	78	No	5	8	No
0.1	17	15	No	80	83	No	4	8	No
0.3	12	17	No	70	75	No	8	6	No
1	14	12	No	66	68	No	4	8	No
3	5	22	Yes	42	64	No	5	7	No
10	0	0	Yes	0	80	Yes	5	9	No
Positive control	1147	1709	No	1453	1617	No	1315	159	No

*solvent control with ethanol

Table 2: Experiment 1 Plate incorporation - Number of revertants per plate (mean of 3 plates)

	TA1537			TA1538
Conc. µl/plate	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	5	6	No	3	8	No
0.1	6	4	No	3	4	No
0.3	5	4	No	2	5	No
1	3	4	No	3	5	No
3	3	6	No	2	8	No
10	0	5	Yes	0	11	Yes
Positive control	230	207	No	1309	1071	No

*solvent control with ethanol

Conclusions:

(3-Trimethoxysilyl)propiononitrile has been tested for mutagenicity to bacteria in a valid and reliable study conducted according to a method that is similar to OECD TG 471 and under GLP. No increase in the number of revertants was observed for the test substance tested up to cytotoxic concentration in any of the Salmonella typhimurium strains tested in the presence or absence of metabolic activation. The experiment was not repeated. It is concluded that the test substance is negative for mutagenicity to bacteria..

Reference 2

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011-08-23 to 2011-10-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.17 (Mutagenicity - In Vitro Mammalian Cell Gene Mutation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5300 - In vitro Mammalian Cell Gene Mutation Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: IWGT Recommendations

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

(Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, Germany)

Type of assay:

mammalian cell gene mutation assay

Target gene:

Thymidine kinase

Species / strain / cell type:

mouse lymphoma L5178Y cells

Details on mammalian cell type (if applicable):

- Type and identity of media: RPMI
- Properly maintained: Yes
- Periodically checked for Mycoplasma contamination: yes
- Periodically "cleansed" against high spontaneous background: yes

Metabolic activation:

with and without

Metabolic activation system:

Liver S9 of Wistar Phenobarbital and ß-Naphthoflavone-induced rat liver S9 mix

Test concentrations with justification for top dose:

Pre-experiment I with and without metabolic activation: 0.1, 0.5, 2.5, 5, 7.5, 10 mM
Pre-experiment II without metabolic activation (24 h long-term exposure): 0.1, 0.5, 2.5, 5, 7.5, 10 mM

Experiment I
with and without metabolic activation: 0.05, 0.1, 0.2, 0.5, 1, 2, 4, 6, 8, 10 mM

Experiment II
with metabolic activation: 0.05, 0.15, 0.3, 0.7, 1.5, 3, 5, 7, 9, 10 mM
without metabolic activation: 0.05, 0.1, 0.2, 0.5, 1, 2, 4, 6, 8, 10 mM

Vehicle / solvent:

DMSO was used as solvent (final concentration in the samples was 1%)

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

benzo(a)pyrene

Remarks:

2.5 µg/ml

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

ethylmethanesulphonate

Remarks:

200 µg/mL and 300 µg/mL

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

10 µg/mL

Details on test system and experimental conditions:

METHOD OF APPLICATION: suspended in DMSO
DURATION: 4 h (short-term exposure), 24 h (long-term exposure)
Expression time (cells in growth medium): 48 h
Selection time (if incubation with selection agent): about 14 days

SELECTION AGENT ( mutation assay) 5 µg/mL trifluorothymidine
NUMBER OF REPLICATIONS: two separate experiments (I+II) with single exposure; cells were seeded in 4 plates and evaluated
NUMBER OF CELLS SEEDED: 2000 cells per well
DETERMINATION OF CYTOTOXICITY: relative total growth (RTG)

Evaluation criteria:

The test item is considered mutagenic if following criteria are met:
-The induced mutant frequency meets or exceeds the Global Evaluation factor (GEF) of 126 per 10^6 cells
- A dose-dependent increase in mutant frequency is detected.

Besides, combined with a positive effect in the mutant frequency, an increased occurrence of small colonies (=40% of total colonies) is an indication for potential clastogenic effects and/or chromosomal aberrations.
According to the OECD guideline, the biological relevance is considered first for the interpretation of results. Statistical methods might be used as an aid in evaluation the test result.
A test item is considered to be negative if the induced mutant frequency is below the GEF and the trend test is negative.

Statistics:

The non-parametric Mann-Whitney test is applied to the mutation data to prove the dose groups for any significant difference in mutant frequency compared to the negative /solvent controls.

Key result

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Conclusions:

In conclusion, in the described mutagenicity test under the experimental conditions reported, the test item 3-(trimethoxysilyl)propiononitrile is considered to be non-mutagenic in the mouse lymphoma thymidine kinase locus using the cell line L5178Y.

Executive summary:

The test item 3-(trimethoxysilyl)propiononitrile was assessed for its potential to induce mutations at the mouse lymphoma thymidine kinase locus using the cell line L5178Y.

The selection of the concentrations used in the main experiments was based on data from the pre-experiments. In experiment I and II 10 mM (with and without metabolic activation) was selected as the highest concentration. Experiment I with and without metabolic activation and experiment II with metabolic activation were performed as a 4 h short-term exposure assay. Experiment II without metabolic activation was performed as a 24 h long-term exposure assay. The test item was suspended in DMSO with a final concentration of 1% v/v in the samples.

The test item was investigated at the following concentrations:

Experiment I

with and without metabolic activation:

0.05, 0.1, 0.2, 0.5, 1, 2, 4, 6, 8, 10 mM

Experiment II

with metabolic activation:

0.05, 0.15, 0.3, 0.7, 1.5, 3, 5, 7, 9, 10 mM

and without metabolic activation:

0.05, 0.1, 0.2, 0.5, 1, 2, 4, 6, 8, 10 mM

No precipitation of the test item was noted in the experiments.

No growth inhibition was observed in experiment I (with and without metabolic activation) and II with metabolic activation. Growth inhibition was observed in experiment II without metabolic activation.

In experiment I with metabolic activation the relative total growth (RTG) was 93.8% for the highest concentration (10 mM) evaluated. The highest concentration evaluated without metabolic activation was 10mM with a RTG of 76.6%. In experiment II with metabolic activation the relative total growth (RTG) was 103.8% for the highest concentration (10 mM) evaluated. The highest concentration evaluated without metabolic activation was 10 mM with a RTG of 33.5%.

In experiment I and II no biologically relevant increase of mutants was found after treatment with the test item (with and without metabolic activation).The Global Evaluation Factor (GEF, defined as the mean of the negative/vehicle mutant frequency plus one standard deviation; based on data gathered from ten laboratories was not exceeded by the induced mutant frequency at any concentration.

No dose-response relationship was observed.

Additionally, in experiment I and II colony sizing showed no clastogenic effects induced by the test item under the experimental conditions (with and without metabolic activation).

EMS, MMS and B[a]P were used as positive controls and showed distinct and biologically relevant effects in mutation frequency. Additionally, MMS and B[a]P significantly increased the number of small colonies, thus proving the efficiency of the test system to indicate potential clastogenic effects.

This study is classified as acceptable. This study satisfies the requirements for Test Guideline OPPTS 870.5300, OECD 476 for in vitro mutagenicity (mammalian forward gene mutation) data.

Reference 3

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003-10-16 to 2003-12-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Deviations:

no

GLP compliance:

yes

Type of assay:

in vitro mammalian chromosome aberration test

Species / strain / cell type:

other: Chinese hamster ovary (CHO-K1) cells

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9

Test concentrations with justification for top dose:

543-2172 µg/ml

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO

- Justification for choice of solvent/vehicle: based on information provided by sponsor and compatibility with target cells

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

mitomycin C

Remarks:

(without activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

(with activation)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION

- Exposure duration: 4 hours (+/- MA); 20 hours (+ MA)

- Expression time (cells in growth medium): 4 hours (+/- MA); 16 hours (+ MA)

- Fixation time (start of exposure up to fixation or harvest of cells): 4 hours (+/- MA); 20 hours (+ MA)

SPINDLE INHIBITOR (cytogenetic assays): Colcemid

NUMBER OF REPLICATIONS: 2 plates for each test concentration

NUMBER OF CELLS EVALUATED: 100 per test concentration

DETERMINATION OF CYTOTOXICITY

- Method: relative total growth

Evaluation criteria:

Toxic effects based on cell growth inhibition and mitotic index relative to solvent control. Number and type of aberrations found recorded. The test substance was considered to induce a positive response when the % of cells with aberrations is increased in a dose-responsive manner with one or more concentrations being statistically significant (p=0.05).

Statistics:

Cell counts and % viability used to determine cell growth inhibition relative to the solvent control. A minimum of 200 metaphase spreads (100 per duplicate flask) were examined and scored for chromatid-type and chromosome-type aberrations. Statistical analysis of % aberrant cells performed using the Fischer's exact test. In the event of a positive Fischer's exact test at any test substance dose level, the Cochran-Armitage test was used to measure dose-responsiveness.

Key result

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: > 2172 µg/ml

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

COMPARISON WITH HISTORICAL CONTROL DATA: Results were within range of historical control data

Table 2:

Results of chromosome analysis Experiment 1, 4h treatment without activation (total count from 2 cultures)

		Solvent* Control***	Positive Control**	543 µg/ml	1086 µg/ml	2172 µg/ml
Cytotoxicity		no	no	no	no	no
		Mean
Chromatid aberrations	gaps	0	0	0	0	0
	breaks	1	19	1	1	1
	exchanges	0	4	0	0	1
Chromosome aberrations	breaks	0	0	0	0	0
	dicentric	1	1	1	0	4
	Ring	0	0	0	0	0
Mitotic index		NR	NR	NR	NR	NR
Polyploidy		NR	NR	NR	NR	NR
Endo reduplication		NR	NR	NR	NR	NR

 *Solvent control with DMSO

** Per 50 cells

*** Per 100 cells

NR not reported

 

Table 3: Results of chromosome analysis Experiment 1, 4h treatment with activation (total count from 2 cultures)

		Solvent* Control***	Positive Control**	543 µg/ml	1086 µg/ml	2172 µg/ml
Cytotoxicity		no	no	no	no	no
		Mean
Chromatid aberrations	gaps	0	0	0	0	0
	breaks	0	4	0	1	1
	exchanges	0	20	0	0	1
Chromosome aberrations	breaks	0	2	0	0	0
	Dicentric	0	0	0	0	0
	Ring	0	0	0	0	0
Mitotic index		NR	NR	NR	NR	NR
Polyploidy		NR	NR	NR	NR	NR
Endo reduplication		NR	NR	NR	NR	NR

 *Solvent control with DMSO

** Per 50 cells

*** Per 100 cells

NR not reported

 

Table 4: Results of chromosome analysis Experiment 1, 20h treatment without activation (total count from 2 cultures)

		Solvent* Control***	Positive Control**	543 µg/ml	1086 µg/ml	2172 µg/ml
Cytotoxicity		no	no	no	no	no
		Mean
Chromatidaberrations	gaps	0	0	0	0	0
	breaks	0	4	0	0	3
	exchanges	0	10	0	0	1
Chromosome aberrations	breaks	0	3	0	0	1
	Dicentric	0	1	0	0	2
	Ring	0	0	1	0	2
Mitotic index		NR	NR	NR	NR	NR
Polyploidy		NR	NR	NR	NR	NR
Endo reduplication		NR	NR	NR	NR	NR

 *Solvent control with DMSO

** Per 50 cells

*** Per 100 cells

NR not reported

 

Conclusions:

In a reliable and valid study, conducted in accordance with OECD 473, under GLP conditions, 3-(triethoxysilyl)propiononitrile was concluded to be negative for the induction of structural and numerical chromosome aberrations in CHO cells in both the activated and non- activated test systems.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In a bacterial mutagenicity study conducted according to a protocol similar to OECD TG 471, no evidence of mutagenicity was observed with or without metabolic activation when (3-trimethoxysilyl)propiononitrile was tested in Salmonella typhimurium strains TA98, TA 100, TA 1535, TA1537 and TA 1538 (Bushy Run Research Center, 1981).

No data are available from an appropriate 5th strain. In view of the lack of genetic toxicity demonstrated in studies on mammalian cells, and the absence of structural features that indicate that such mutagenicity is likely, testing in an appropriate 5th strain is not considered necessary. In addition, many of the organosilicon substances have been tested in an appropriate 5th strain, and the only organosilicon substance which has given a positive result in a bacterial strain capable of detecting cross-linking or oxidising mutagens contains an epoxy- side-chain (which is a structural feature associated with cross-linking mutagenicity), and this substance was positive in Salmonella typhimurium strains TA 100, TA 1535 as well as in E.coli WP2 uvrA. It is therefore considered that for all the organosilicon substances, whether or not the structure includes structural alerts for genetic toxicity (Benigni et al, 2008), genetic toxicity would be detected in Salmonella typhimurium strains TA 98, TA 100, TA 1535 or 1537.

In a cytogenicity study conducted according to OECD TG 473 and under GLP, no evidence of the induction of chromosome aberration was observed when the analogous substance, 3-(triethoxysilyl)propiononitrile, was tested with or without metabolic activation in CHO K1 cells (BioReliance, 2004).

3-(Trimethoxysilyl)propiononitrile has been tested for mutagenicity to mammalian cells in a study conducted according to OECD TG 476. No increase in mutant frequency was observed when the substance was tested in L5178Y cells with and without metabolic activation (BSL Bioservice, 2011).

In vivo testing is not required as no evidence for genetic toxicity was found in the in vitro studies.

Read-across justification

There are no available measured data for 3-(trimethoxysilyl)propiononitrile (CAS 2526-62-7) for in vitro cytogenicity. Therefore, the Annex requirements are fulfilled with data on a structural analogous substance. This section describes the analogue approach for fulfilling this endpoint by read-across from the source substance, 3-(triethoxysilyl)propiononitrile (CAS 919-31-3), according to the Read-Across Assessment Framework (RAAF)¹.

Read-across is proposed in accordance with RAAF Scenario 1: “This scenario covers the analogue approach for which the read-across hypothesis is based on (bio)transformation to common compound(s). For the REACH information requirement under consideration, the property investigated in a study conducted with one source substance is used to predict the properties that would be observed in a study with the target substance if it were to be conducted. Similar properties or absence of effect are predicted. The predicted property may be similar or based on a worst-case approach.”

The read-across justification is presented (Table 1) according to RAAF scenario 1 assessment elements (AE) as outlined in Table A1 of the RAAF¹:

Table 1 RAAF scenario 1 assessment elements (AE) as given in Appendix A (Table A1) of the RAAF¹

AE A.1	Characterisation of source substance
AE A.2	Link of structural similarity and differences with the proposed prediction
AE A.3	Reliability and adequacy of the source study
AE 1.1	Compounds the test organism is exposed to
AE 1.2	Formation of common (identical) compound(s)
AE 1.3	Exposure of the biological target(s) to the common compound(s)
AE 1.4	The impact of parent compounds
AE 1.5	Formation and impact of non-common compounds
AE A.4	Bias that influences the prediction

 

1.   AE A.1 Identity and characterisation of the source substance

The source substance, 3-(triethoxysilyl)propiononitrile (CAS 919-31-3), is a triethoxysilane with a propiononitrile side-chain. Its measured hydrolysis half-lives are: <0.5 h at pH 4, 6.5 h at pH 7, <0.5 h at pH 9, and 20°C (OECD 111). At physiological temperature 37.5ºC and pH 7 (relevant for genetic toxicity testing), the hydrolysis half-life is calculated as 1.6 h. The products of hydrolysis are 3-(hydroxysilyl)propiononitrile and ethanol.

The source substance has log Kow of 1.7 (QSAR), water solubility of 4000 mg/l (QSAR) and vapour pressure of 1.9 Pa at 20°C (measured).

Table 2 Summary of the structure and purity for the target 3-(trimethoxysilyl)propiononitrile (CAS 2526-62-7) and source 3-(triethoxysilyl)propiononitrile (CAS 919-31-3)

		Target		Source
Chemical name		3-(trimethoxysilyl)propiononitrile		3-(triethoxysilyl)propiononitrile
CAS Number		2526-62-7		919-31-3
EC Number		219-764-3		213-050-5
Chemical structure		CO[Si](CCC#N)(OC)OC		CCO[Si](OCC)(OCC)CCC#N
Type		Monoconstituent		Monoconstituent
Purity (w/w)		= 95% = 100% w/w		= 90% = 100% w/w

 

Analytical data that was provided by members of the Reconsile consortium is the basis of the published Substance Identity Profiles (SIPs) and boundary compositions for these substances. The precise identity of the impurities is considered confidential because it could reveal details of the manufacturing process to other consortium members.

The classification and labelling of each impurity has been checked using the ECHA CLP inventory and (for silicon containing compounds) the consortium’s own dataset. None of the impurities are considered to be potential SVHC. None of the impurities will impact the classification and labelling of the substances.

2.  AE A.2 Link of structural similarities and differences with the proposed prediction

The registration substance, 3-(trimethoxysilyl)propiononitrile, and the source substance, 3-(triethoxysilyl)propiononitrile, are both trialkoxysilanes with a propiononitrile side-chain. The difference between the two substances is that the three alkoxy groups are methoxy for the target substance and ethoxy for the source substance.

Therefore, the target and source substances are structurally similar and have similar physicochemical properties (Table 3). Both have low vapour pressure (4.7 and 1.9 Pa at 25°C), moderate log Kow (0.2 and 1.7) and moderate to high water solubility (130000 and 4000 mg/l). Both hydrolyse fairly rapidly (half-life 0.4 h and 1.6 h at pH 7 and 37.5°C) to give a common hydrolysis product, 3-(hydroxysilyl)propiononitrile. The non-common hydrolysis products are methanol and ethanol, which will not contribute to genetic toxicity.

Table 3 Physicochemical properties

Property		Target substance		Source substance
Substance name		3-(trimethoxysilyl)propiononitrile		3-(triethoxysilyl)propiononitrile
CAS number		2526-62-7		919-31-3
Hydrolysis half-life at pH 4 and 25°C		0.1 h (QSAR)		<0.5 h (OECD 111)
Hydrolysis half-life at pH 7 and 25°C		1.1 h (QSAR)		6.5 h (OECD 111)
Hydrolysis half-life at pH 7 and 37.5°C		0.4 h(extrapolation)		1.6 h (extrapolation)
Silanol hydrolysis product		3-(hydroxysilyl)propiononitrile		3-(hydroxysilyl)propiononitrile
Non-Si hydrolysis product		Methanol		Ethanol
Log Kowvalue		0.2 (QSAR)		1.7 (QSAR)
Vapour pressure		4.7 Pa at 25°C (QSAR)		1.9 Pa at 25°C (measured)
Water solubility		130000 mg/l (QSAR)		4000 mg/l (QSAR)

 

3.  AE A.3 Reliability and adequacy of the source study

To support the read-across there are reliable data on the source substance for most required toxicological endpoints relevant for the Annex level. Reliable data are available for acute toxicity, skin and eye irritation, skin sensitisation, genetic toxicity (in vitro), and repeated dose toxicity (oral) that can be compared with available reliable data of the target substance. Table 4 summarises the key data and their reliability (using Klimisch codes).

Of particular importance in this case is the reliability of the genotoxicity study that is being read-across. An in vitro cytogenicity study is available for 3-(triethoxysilyl)propiononitrile (CAS 919-31-3), conducted according to OECD TG 473 and under GLP (BioReliance, 2004). No evidence of the induction of chromosome aberration was observed with or without metabolic activation in CHO K1 cells when tested up to limit concentration. The purity of the test substance used in the study was 99.9% and it was considered to represent the source substance without impurities that could influence the outcome of the study. The test is considered adequate for the purpose of classification and labelling and risk assessment.

Table 4 Summary of reliability of the key data for the target substance 3-(trimethoxysilyl)propiononitrile (CAS 2526-62-7) and source substance 3-(triethoxysilyl)propiononitrile (CAS 919-31-3)

	Target	Source
	3-(trimethoxysilyl)propiononitrile	3-(triethoxysilyl)propiononitrile
	2526-62-7	919-31-3
1. Acute Toxicity
Oral	LD50 9555 mg/kg bw (male) and 10961 mg/kg bw (female) Reliability 2 study (Bushy Run Research Center, 1982)	LD50 5600 mg/kg bw (male) (median-effect dose, calculated from the 14-day mortality data) Reliability 2 study (Mellon Institute, 1956)
Inhalation	No reliable data	No reliable data
Dermal	LD50>15520 mg/kg bw Reliability 1 study (Bushy Run Research Center, 1982)	LD50 5753 mg/kg bw Reliability 2 study (Mellon Institute, 1956)
2. Irritation
Skin	Not irritating in vivo Reliability 2 study (Bushy Run Research Center, 1982)	No data
Eye	Not irritating in vivo Reliability 2 study (Bushy Run Research Center, 1982)	No data
3. Skin sensitisation	No data	Skin sensitization (Guinea pig maximisation method) in vivo – negative Reliability 1 study (Arcelin, 2010,)
4. Genetic toxicity
In vitro	Bacterial mutagenicity test - negative with and without metabolic activation all strains Reliability 2 study (Bushy Run Research Center, 1981) Mammalian cytogenicity test – no data Mammalian mutagenicity - negative Reliability 1 study BSL Bioservice, 2011	Bacterial mutagenicity test - negative Reliability 1 study (BioReliance, 2004a) Mammalian cytogenicity test – negative Reliability 1 study (BioReliance, 2004b) Mammalian mutagenicity test – no data
In vivo	No data	No data
5. Repeated dose toxicity
Oral	90-day repeated dose oral (gavage) toxicity study – NOAEL (systemic)=100 mg/kg bw/day (male/female) (based on tubulopathy observed at doses of 1000 and 300 mg/kg bw/day) Reliability 1 study (Eurofins, 2019)	28-day repeated dose oral (gavage) toxicity study – NOAEL (systemic)=100 mg/kg bw/day (nominal) (male/female) (based on increased organ weights and kidney effects at the 500 mg/kg bw/day (nominal) dose Reliability 1 study (RCC, 2005)
Inhalation	No data	No data
Dermal	No data	No data
6. Reproductive toxicity
	No data	28-day studyNOAEL (P): 1000 mg/kg bw/day (male/female) NOAEL (F1): 1000 mg/kg bw/day (male/female) Reliability 1 study (RCC, 2005)
7. Developmental toxicity
	NOAEL (developmental toxicity): 1000 mg/kg bw/day Reliability 1 study (Eurofins, 2019)	28-day study NOAEL (maternal toxicity): 1000 mg/kg bw/day NOAEL (teratogenicity): 1000 mg/kg bw/day Reliability 1 study (RCC, 2005)

 

4.  AE A.4 Compounds the test organism is exposed to

Under conditions relevant for in vitro genetic toxicity testing (pH 7 and 37.5°C), both the target and source substances hydrolyse moderately rapidly (half-life 0.4 h for the target substance and 1.6 h for the source substance). Therefore, the test organism may be exposed to the parent substances and their silanol hydrolysis product, 3 -(hydroxysilyl)propiononitrile. The source and target substances and the silanol hydrolysis product have been profiled using the OECD QSAR Toolbox v. 4.1. The substances and their common silanol hydrolysis product show similar profiles for all toxicological endpoints. No alert for genetic toxicity was detected by OECD QSAR Toolbox v.4.1.

There is no significant evidence that ethanol is genotoxic based on results from bacterial mutagenicity studies, cytogenicity and mutagenicity tests in mammalian cell lines according to the criteria applied normally for the purposes of classification and labelling.

Methanol has been examined in numerous tests including bacterial, mammalian and fungal test systems. Most studies failed to demonstrate mutagenic activity.

5.  AE 1.2 and 1.3 Formation of common (identical) compound(s) and Exposure of the biological target(s) to the common compound(s)

No in vitro cytogenicity data are available for the target substance, 3-(trimethoxysilyl)propiononitrile, therefore data are read-across from the source substance, 3-(triethoxysilyl)propiononitrile. The registration and the source substances are both trialkoxysilanes with a propiononitrile side-chain. Both substances hydrolyse to the same silicon-containing hydrolysis product, 3-(hydroxysilyl)propiononitrile at similar rates. Their non-silanol hydrolysis products are methanol and ethanol, respectively, neither of which is considered to contribute to the genetic toxicity potential of the target or source substance.

The available key toxicity data on the source substance and target substance are summarised in Table 4. Neither of the two substances is acutely toxic via oral or dermal route, nor are they irritating to skin or eyes. It has been demonstrated that the source substance is not sensitising to skin. Both substances have been tested for mutagenicity in bacteria and they gave negative results. The source substance also gave negative results in an in vitro cytogenicity test in mammalian cells. Similarly, the target substance was concluded to be negative for mutagenicity to mammalian cells when tested in vitro. The available repeated dose toxicity data for the two substances indicate that kidney effects predominate the systemic toxic effects in rats. These data support the hypothesis that the target and source substances and/or their silanol hydrolysis products have similar biological reactivity and are therefore expected to have the same genotoxicity profile, and support read-across of the in vitro cytogenicity test.

6.  AE1.4 The impact of parent compounds

Since the registration and the source substance are both trialkoxysilanes with a propiononitrile side-chain, they both have the nitrile functionality. Therefore, as already demonstrated in Sections A.4 1.2 and 1.3 of this read-across justification, both substances are expected to have similar genotoxicity profiles. This hypothesis is supported by existing bacterial genotoxicity test data on the target and source substances, in vitro mammalian mutagenicity for the target substance and in vitro cytogenicity data, for which all results were negative.

7.  AE 2.5 Occurrence of Other Effects than Covered by the Hypothesis and Justification

Not relevant.

8.  AE A.4 Bias that influences the prediction

Possible analogue substances were identified by searching the database of studies held by the Reconsile consortium and by searching in the OECD QSAR Toolbox. The databases were filtered for substances containing both an alkoxysilane and a nitrile group. The source substance was identified as the only suitable substance with reliable in vitro cytogenicity data.

[1] European Chemicals Agency (ECHA) (2015) Read-across Assessment Framework. Appendix A, Scenario 1.

Justification for classification or non-classification

The available information for the substance indicates that, when tested in vitro, 3-(trimethoxysilyl)propiononitrile does not induce mutations in bacterial or mammalian cells. The related substance 3-(triethoxysilyl)propiononitrile does not induce chromosome aberrations in mammalian cells. There is no justification from in vitro results for testing in vivo. Therefore, it is considered that classification for mutagenicity is not required according to Regulation 1272/2008/EC.