[3-(trimethoxysilyl)propyl]urea

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Genetic toxicity in vitro:

Bacterial mutagenicity (Ames test, OECD 471): S. typhimurium TA 98, TA 100, TA 1535, TA 1537 and E. coli WP2 uvrA: negative with and without metabolic activation

Mammalian cytogenicity (Chromosome Aberration, OECD 473): positive with and without metabolic activation (RA from CAS 116912-64-2)

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:

22 Feb - 04 Apr 1996

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

yes

Remarks:

2-aminoanthracene was used as the only positive control in the presence of S9-mix, at least a second positive control substance must be included for the efficacy testing of S9-mix.

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Target gene:

his operon (for S. typhimurium strains) and trp operon (for E. coli strain)

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Additional strain / cell type characteristics:

not applicable

Species / strain / cell type:

E. coli WP2 uvr A

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9

Test concentrations with justification for top dose:

Preliminary toxicity test:
- 6.7, 10, 33, 67, 100, 333, 667, 1000, 333 and 5000 µg/plate (with and without metabolic activation, TA 100 and E. coli WP2 uvrA)
Experiment I+II:
- 100, 333, 1000, 3333 and 5000 µg/plate (with and without metabolic activation)
Experiment III:
- 100, 333, 1000, 3333 and 5000 µg/plate (TA 100 without metabolic activation)
5000 µg/plate is the highest recommended dose level based on the current OECD guideline

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Acetone
- Justification for choice of solvent/vehicle: Solubility properties and relative non-toxicity to bacteria

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: +S9-mix: 2-aminoanthracene (2-AA); -S9-mix: 2-nitrofluorene (2-NF), sodium azide (NaN), 9-aminoacridine (9-AA), methyl methanesulfonate (MMS)

Remarks:

2-AA: 1 µg/plate (all TA strains), 10 µg/plate (E. coli WP2 uvrA), 2-NF: 1 µg/plate (TA 98), NaN: 1 µg/plate (TA 100, TA 1535), 9-AA: 75 µg/plate (TA 1537), MMS: 1000 µg/plate (E. coli Wp2 uvrA)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar ; preincubation

DURATION
- Preincubation period: 60 min
- Expression time (cells in growth medium): 48 h

NUMBER OF REPLICATIONS: 3 plates for each test concentration in two independent experiments

DETERMINATION OF CYTOTOXICITY
- Method: A dose level is considered toxic if one or both of the following criteria are met: a >50 % reduction in the mean number of revertants per plate as compared to the mean vehicle control - this reduction must be accompanied by an abrupt dose-dependent drop in the revertant count and/or a reduction in the background lawn.

Evaluation criteria:

The mean of each positive control must exhibit at least a three-fold increase in the number of revertants over the mean value of the respective vehicle control. A minimum of three non-toxic dose levels are required to evaluate assay data. For the test material to be evaluated positive, it must cause a dose-related increase in the mean revertants per plate of at least one tester strain with a minimum of two increasing concentrations of test material. Data sets for strains TA 1535 and TA 1537 were judged positive if the increase in mean revertants at the peak of the dose response is equal to or greater than three times the mean vehicle control value. Data sets for strains TA 98, TA 100 and E. coli WP2 uvrA were judged positive if the increase in mean revertants at the peak of the dose is equal to or greater than two times the mean vehicle control value.

Statistics:

Mean values and standard deviation were calculated.

Key result

Species / strain:

S. typhimurium, other: TA 1535, TA 1537, TA 98 and TA 100

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:

E. coli WP2 uvr A

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

Additional information on results:

COMPARISON WITH HISTORICAL CONTROL DATA: All results of the vehicle and positive controls as well as the test groups were within range of historical control data.

Table 2: Dose range-finding study Number of revertants per plate (2 plates per strain)

	TA 100			WP2 uvrA
Concentration (µg/Plate)	Plate 1 + MA	Plate 2 - MA	Cytotoxic (Yes/No)	Plate 1 + MA	Plate 2 - MA	Cytotoxic (Yes/No)
0	142	112	No	13	16	No
6.7	138	119	No	16	20	No
10	126	101	No	9	18	No
33	146	128	No	15	16	No
67	129	105	No	12	16	No
100	140	109	No	8	12	No
333	127	112	No	12	16	No
667	111	119	No	5	13	No
1000	125	120	No	12	12	No
3333	133	129	No	10	12	No
5000	144	121	No	13	14	No

*solvent control with Acetone

MA: metabolic activation (S9 -mix)

Table 3: Experiment 1 Mutagenicity Assay Number of revertants per plate (mean of 3 plates)

	TA98			TA100			TA1535
Conc.µg/plate	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	14	24	No	125	156	No	12	9	No
100	18	23	No	125	143	No	9	15	No
333	26	30	No	133	159	No	12	11	No
1000	21	37	No	139	169	No	11	12	No
3333	23	31	No	133	162	No	9	11	No
5000	24	31	No	129	169	No	8	14	No
Positive control	523	2672	No	910	2698	No	673	285	No

*solvent control with Acetone

MA: metabolic activation (S9 -mix)

Table 4: Experiment 1 Mutagenicity Assay Number of revertants per plate (mean of 3 plates)

	TA1537			WP2uvrA
Conc. µg/plate	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	7	9	No	14	17	No
100	8	7	No	19	15	No
333	7	10	No	18	20	No
1000	6	10	No	20	18	No
3333	6	10	No	17	19	No
5000	6	10	No	20	15	No
Positive control	736	424	No	610	204	No

*solvent control withAcetone

MA: metabolic activation (S9 -mix)

Table 5: Experiment 2 Mutagenicity Assay Number of revertants per plate (mean of 3 plates)

	TA98			TA100			TA1535
Conc. µg/plate	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	13	15	No	116	98	No	8	10	No
100	13	15	No	114	84	No	7	9	No
333	12	16	No	116	97	No	9	8	No
1000	16	16	No	232	82	No	7	9	No
3333	17	19	No	125	95	No	5	9	No
5000	14	18	No	137	92	No	5	11	No
Positive control	248	876	No	638	891	No	227	134	No

*solvent control withAcetone

MA: metabolic activation (S9 -mix)

Table 6: Experiment 2 Mutagenicity Assay Number of revertants per plate (mean of 3 plates)

	TA1537			WP2 uvrA
Conc. µg/plate	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	6	4	No	12	11	No
100	2	3	No	8	9	No
333	2	4	No	10	10	No
1000	4	4	No	9	13	No
3333	5	4	No	10	11	No
5000	5	5	No	11	10	No
Positive control	226	147	No	369	45	No

*solvent control withAcetone

MA: metabolic activation (S9 -mix)

Conclusions:

Under test conditions with GLP, no mutagenic effect and no cytotoxicity was observed for the test substance tested up to limit concentration in any of the test strains without and with metabolic activation in the Ames test. The test substance is non mutagenic in the strains used.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Species / strain:

lymphocytes: human

Metabolic activation:

with and without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

=420 µg/ml (-S9-mix); =1000 µg/ml (+S9-mix)

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: pH 7.54 was measured at the highest concentration of 5000 µg/ml in the preliminary toxicity test (pH 7.67 in the solvent control)
- Effects of osmolality: 385 mOsm/kg was measured at the highest concentration of 5000 µg/ml in the preliminary toxicity test (428 mOsm/kg in the solvent control)

RANGE-FINDING/SCREENING STUDIES: for details see table 1

COMPARISON WITH HISTORICAL CONTROL DATA: Solvent control data were within the historical control data

Conclusions:

In a chromosomal aberration assay according to OECD 473 and GLP, a genotoxic effect was observed for the source substance tested in a 3 h treatment (single experiment) with and without metabolic activation. Appropriate solvent and positive controls were included and gave expected results. As explained in the analogue justification, the differences in molecular structure between the target and the source are unlikely to lead to differences in genetic toxicity.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (positive)

Genetic toxicity in vivo

Description of key information

Genetic toxicity in vivo:

Mammalian cytogenicity (Mammalian Erythrocyte Micronucleus Test, OECD 474): negative with and without metabolic activation (RA from CAS 116912-64-2)

Link to relevant study records

Reference

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE-FINDING STUDY
- Dose range: 2000 mg/kg bw
- Clinical signs of toxicity in test animals: No abnormalities were observed within 3 days.
- Evidence of cytotoxicity in tissue analyzed: No abnormalities were observed.

RESULTS OF DEFINITIVE STUDY
- Induction of micronuclei: No induction was observed.
- Ratio of PCE/NCE: No change of the ratio was observed after treatment with test substance. A decrease of the PCE/NCE ratio was observed after treatment with cyclophosphamide.

Conclusions:

The source substance has been tested according to OECD 474 and under GLP conditions. No significant increase in the incidence of micronucleated polychromatic erythrocytes was observed in the bone marrow of male or female rats 24 or 48 hours after a single oral dose of up to and including 2000 mg/kg bw. A reduction in the PCE/total erythrocyte ratio was only observed in the 48 hour positive control group. It is concluded that the source substance is negative for the induction of micronuclei under the conditions of the study. As explained in the analogue justification, the differences in molecular structure between the target and the source are unlikely to lead to differences in genetic toxicity.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Only limited data on genetic toxicity with 1-[3-(trimethoxysilyl)propyl]urea (CAS 23843-64-3) are available. Therefore, the risk assessment was performed based on the available data from the source substance ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters (CAS 116912-64-2). The source substance is the reaction mass of 1-[3-(trimethoxysilyl)propyl]urea, [3-(dimethoxyethoxysilyl)propyl]urea, [3-(methoxydiethoxysilyl)propyl]urea and 1-[3-(triethoxysilyl)propyl]urea and therefore contains the target substance as one of its components. In accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5 “Grouping of substances and read across” and in accordance with the Read across assessment framework (RAAF, ECHA 2017) read across from the analogue substance has been applied to support the human health hazard assessment of 1-[3-(trimethoxysilyl)propyl]urea (CAS 23843-64-3).  Details on read across justifications can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.

Genetic toxicity (mutagenicity) in bacteria in vitro

A genetic toxicity study addressing mutagenicity in bacteria with 1-[3-(trimethoxysilyl)propyl]urea (CAS 23843-64-3) is available and was performed according to OECD 471 (Ames test) and in compliance with GLP (Microbiological Associates, 1996).The strains Salmonella typhimurium TA 1535, TA 1537, TA 98, TA 100 and E.coli WP2 uvr A were tested in two independent experiments according to the plate incorporation and pre-incubation procedure in the absence and presence of a metabolic activation system (Aroclor 1254-induced rat liver S9-mix). Both experiments were conducted in three repetitions at each concentration from 100 to 5000 µg/plate (vehicle: acetone). No significant increase in the number of revertants was observed in any of the tester strains with and without metabolic activation. No cytotoxicity was observed at any of the tested concentrations. Appropriate solvent and positive controls were included and gave the expected results. Hence, the test item was considered to be not mutagenic in bacteria under the conditions of the test.

 

Genetic toxicity (cytogenicity) in mammalian cells in vitro

Mammalian cytogenicity of ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters (CAS 116912-64-2) was assessed in vitro in a study according to OECD 473 under GLP conditions (NOTOX, 2000c). Human peripheral lymphocytes were cultured and treated with the test material or vehicle (0.9% DMSO) in the absence or presence of a metabolic activation system (Aroclor-induced rat liver S9-mix) at duplicates at each concentration of 100, 180, 333, 420 and 560 µg/ml (without S9-mix) and of 333, 560, 1000 and 1800 µg/ml (with S9-mix) for 3 h. Fixation and staining of the cells were performed 24 h after start of exposure with the test material. Cytotoxicity was assessed by determination of the mitotic index. Appropriate solvent and positive controls were included in the test and gave the expected results. Cytotoxicity was recorded at the highest tested concentration with and without metabolic activation. Moreover, a genotoxic effect was observed for the test material tested in a 3 h treatment in two independent experiments without and with metabolic activation. It is therefore concluded that the test substance is positive for the induction of chromosome aberrations in the presence and absence of S9-mix in vitro under the conditions of the study. To clarify the observed positive outcome in this study an additional study on genetic toxicity in vivo is presented.

  

Genetic toxicity (cytogenicity) in vivo

An in vivo chromosome aberration test (mammalian erythrocyte micronucleus assay) with ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters (CAS 116912-64-2) was performed according to OECD 474 and in compliance with GLP (NOTOX, 2001). The test material was administered via single oral gavage to 5 Wistar rats of each sex and dose group at nominal concentrations of 500, 1000, and 2000 mg/kg bw. Bone marrow cells were freshly isolated 24 and 48 hours post-application. The ratio of polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE) was determined by counting and differentiating isolated and fixed erythrocytes. Appropriate negative (0.9% NaCl) and positive controls (50 mg/kg bw cyclophosphamide) were included in the study and showed the expected result. No significant increase in the incidence of micronucleated polychromatic erythrocytes was observed in the bone marrow of male or female rats 24 or 48 hours post-administration. Based on the results of the study the test substance is negative for the induction of micronuclei under the conditions of the test.

 

Conclusion

Taking into consideration the negative results in both the bacterial mutagenicity test in vitro and the mammalian erythrocyte micronucleus study in rats the registered substance is not considered to produce genetic toxicity.

Justification for classification or non-classification

The available data on genetic toxicity of the registered substance do not meet the criteria for classification according to Regulation (EC) No 1272/2008 and are therefore conclusive but not sufficient for classification.