Carbamic acid, N-[(dimethoxymethylsilyl)methyl]-, methyl ester

Endpoint summary

Description of key information

RDT oral (OECD 407): NOAEL = 150 mg/kg bw/day (males/females) 
RDT inhalation: no data available
RDT dermal: no data available

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 Sep - 30 Oct 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Version / remarks:

(1995)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayrisches Landesamt für Arbeitsschutz, Arbeitsmedizin und Sicherheitstechnik

Limit test:

no

Species:

rat

Strain:

other: Hsd: Wistar rats (HsdBrl:WH, Full-Barrier)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Winkelmann GmbH, Borchen, Germany
- Age at study initiation: 7 – 9 weeks
- Weight at study initiation: 130 – 151 g (females), 163 – 186 g (males)
- Housing: Animals were caged in macrolon cages on Altromin saw fiber bedding.
- Diet: Altromin 1324 maintenance diet for rats and mice, ad libitum
- Water: (tap/filtered) water, ad libitum
- Acclimation period: adequate period

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 55 ± 10
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

VEHICLE
- Amount of vehicle (if gavage): 5 mL/kg bw
- Justification for choice of vehicle: The vehicle was chosen due to its non-toxic characteristics and the chemical properties of the test item.
- Lot/batch no.: 062K0006

MAXIMUM DOSE VOLUME APPLIED: 5 mL/kg bw

DOSAGE PREPARATION: The test substance was suspended in corn oil. The homogeneity of the preparations was visually checked. During the application procedure no obvious separation was checked.

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

Not applicable

Duration of treatment / exposure:

28 days

Frequency of treatment:

once daily, 7 days/week

Dose / conc.:

150 mg/kg bw/day (actual dose received)

Dose / conc.:

500 mg/kg bw/day (actual dose received)

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: based on a previous dose range finding study

Positive control:

Not required

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: at least once a day for general health condition and at least twice a day for mortality and morbidity

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: once before the first exposure and in the final week

BODY WEIGHT: Yes
- Time schedule for examinations: Days 0, 7, 14, 21, 27

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each group determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

HAEMATOLOGY: Yes
- Time schedule for collection of blood: during necropsy
- Anaesthetic used for blood collection: Yes
- Animals fasted: Yes
- How many animals: all animals (20)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: during necropsy
- Animals fasted: Yes
- How many animals: all animals (20)

URINALYSIS: Yes
- Time schedule for collection of urine: during necropsy
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: once before the first exposure and in the final week
- Dose groups that were examined: all
- Battery of functions tested: Standard functional observational battery according to Moser et al (1991): sensory activity / grip strength / motor activity

Sacrifice and pathology:

GROSS PATHOLOGY: Yes, all animals
ORGAN WEIGHTS: Yes, all animals (liver, kidneys, adrenals, testes, epididymides, thymus, spleen, brain, heart)
HISTOPATHOLOGY: Yes, all animals of control and high dose groups (all gross lesions, brain (representative regions including cerebrum, cerebellum and pons), spinal cord, liver, kidneys, adrenals, stomach, small and large intestines (including Peyer's patches, lymphnodes acc. to application), thymus, thyroid, spleen, lung and trachea, heart, gonades, acc. sex organs (e.g. uterus, prostate, vesicula seminalis), urinary bladder, lymph nodes (lymphocentrum mandibulare; Lnn. axillares), peripheral nerve, bone marrow)

Statistics:

For statistical analysis one-way analysis of variance (ANOVA) was carried out, followed by Student's t-test to reveal any differences between control and test groups. For parameters indicating no compound-related alterations and/or showing a high degree of variation (both in control and test groups) no statistical evaluation was carried out.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

500 mg/kg bw/day: Hypoproteinaemia (males/females), reduced cholesterol (males);
1000 mg/kg bw/day: Hypoproteinaemia (males), reduced cholesterol (males)

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

150 mg/kg bw/day: decreased rel. thymus weight (males, non-adverse)
500 mg/kg bw/day: decreased rel./abs. adrenals/thymus weight (males/females, adverse);
1000 mg/kg bw/day: decreased rel./abs. adrenals (males, adverse)/thymus weight (males/females, adverse)

Gross pathological findings:

no effects observed

Neuropathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

1000 mg/kg bw/day: splenic peritonitis and thymic atrophy (males/females), testicular tubular degeneration and epididymal hypospermia (males)

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
There were no mortality and no severe clinical signs observed throughout the study period.

BODY WEIGHT AND WEIGHT GAIN
Body weight development was unaffected by treatment.

FOOD CONSUMPTION
Food consumption was unaffected by treatment.

HAEMATOLOGY
There were no effects of toxicological relevance noted on haematology parameters such as haemoglobin (Hb), haematocrit (Hct), erythrocyte count (RBC), blood clotting and different leucocyte count.
Significant decrease of total leucocyte count (WBC) was noted for medium dose males (500 mg/kg bw/day); however, the biological relevance is equivocal as no other findings were observed confirming disturbance in the white blood cell system. Significantly decreased platelet counts were noted for high dose (1000 mg/kg bw/day) males and females (68.9 and 71.6% as compared to the control group) and medium dose (500 mg/kg bw/day) males (65.6% as compared to the control group), respectively. However, toxicological relevance was considered equivocal, especially as high values were also observed in the male control group.

CLINICAL CHEMISTRY
There were no effects of toxicological relevance noted on clinical chemistry parameters such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AP), glucose (GLU), urea, creatinine (CREA), albumin (ALB), natrium and kalium. Two dosed male groups (medium and high dose) showed significant reduced CHOL-values. Toxicological relevance of this finding is equivocal. Compound relation and dose dependency may be assumed although all values are within the expected range. Significant differences in total protein are found for the male medium and high dose and female medium dose, but not for the female high dose. Hypoproteinaemia is normally observed with chronic hepatic disturbance, nephrotic disturbance or reduced protein synthesis, e.g. due to malassimilation. As the mean values of both, female and male high dose groups, are less than the expected range compound relation and dose dependency may be assumed.

URINALYSIS
There were no effects of toxicological relevance noted on any of the tested urinalysis parameters.

NEUROBEHAVIOUR
There were no effects noted concerning functional and behavioural examination.

ORGAN WEIGHTS
The mean absolute and relative adrenals weight in the male medium and high dose (500, 1000 mg/kg bw/day) groups, as well as the mean absolute adrenals weight in the female medium dose group was slightly lower than the adrenals weight in the corresponding control groups, reaching statistical significance (p<0.05). This finding is assumed to be compound related, indicating a possible disturbance in the endocrine system.
The mean absolute and relative thymus weight in the male and female medium and high dose groups, as well as the mean relative thymus weight in the male low dose (150 mg/kg bw/day) group was reduced compared to the thymus weight in the corresponding control groups, reaching statistical significance (p<0.05). This finding is assumed to be compound related for the medium and high dose group and was confirmed by the histopathological findings for the high dose groups. Beside the physiological atrophy in older animals, reduction of thymus weight (thymic atrophy) is normally observed with disturbance of the immunological system.
The mean absolute and relative testes weight in the male high dose (1000 mg/kg bw/day) was lower than the testes weight in the control group, reaching statistical significance (p<0.05). This finding is assumed to be compound related, and was confirmed by the histopathological assessment.
The mean absolute and relative epididymides weight in the male high dose (1000 mg/kg bw/day) was lower than the epididymides weight in the control group, reaching statistical significance (p<0.05). This finding is assumed to be compound related, and was confirmed by the histopathological assessment.

GROSS PATHOLOGY
Disseminated white depositions on the spleen surface were observed of two males of the medium dose group (500 mg/kg bw/day), of three females and all males of the high dose group (1000 mg/kg bw/day).

HISTOPATHOLOGY: NON-NEOPLASTIC
There were treatment-related lesions in the spleen and thymus of both sexes and the thyroids, epididymides and testes of male rats. Significant incidences of splenic peritonitis and thymic atrophy were limited to the high dose group (1000 mg/kg bw/day). Treatment-related lesions of follicular cell hypertrophy were present in the thyroids of male rats of the high dose group. Testicular tubular degeneration and epididymal hypospermia and degenerate sperm forms (all at a minimal or mild level) were only present in high dose group males. The treatment-related findings were of a minor degree in each organ. There were insignificant incidences of splenic focal fibrous peritonitis, thymic atrophy and thyroid follicular cell hypertrophy in the medium dose group (500 mg/kg bw/day). The histopathological “no-effect” level of treatment with the test material over a period of 28 days was established to be 500 mg/kg.

Key result

Dose descriptor:

NOAEL

Effect level:

150 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Overall effects: organ weights; adrenals, thymus, testes and epididymides histopathology; lesions in the spleen, thymus, thyroid, testes and epididymides clinical chemistry; hypoproteinaemia

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

500 mg/kg bw/day (actual dose received)

System:

immune system

Organ:

spleen

thymus

thyroid gland

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

1 000 mg/kg bw/day (actual dose received)

System:

male reproductive system

Organ:

cauda epididymis

testes

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

1 000 mg/kg bw/day (actual dose received)

System:

endocrine system

Organ:

adrenal glands

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Table 1: Procentual mean TP values

Procentual Mean Biochemistry Value			TP
Group	Sex	Mean		%
		g/L
C	m	56.82		100
C	f	55.80		100
LD	m	56.66		99.72
LD	f	56.02		100.39
MD	m	53.02	*	93.31
MD	f	51.80	*	92.83
HD	m	50.18	*	88.31
HD	f	50.96		91.33

* significant (p<0.05); as determinded with the individual values

C: control

LD: low dose

MD: medium dose

HD: high dose

TP: total protein

m: male

f: female

Table 2: Procentual mean absolute and relative organ weight adrenals, thymus, testes and epididymides

Procentual mean absolute and relative organ weight
Adrenals
Group	Sex	Absolute		Relative		% absolute	% relative
		mean in g		mean in %
C	m	0.051		0.018		100.00	100.00
C	f	0.061		0.035		100.00	100.00
LD	m	0.046		0.017		90.20	94.44
LD	f	0.056		0.032		91.80	91.43
MD	m	0.037	*	0.013	*	72.55	72.22
MD	f	0.045	*	0.025		73.77	71.43
HD	m	0.037	*	0.013	*	72.55	72.22
HD	f	0.053		0.031		86.89	88.57
Thymus
Group	Sex	Absolute		Relative		% absolute	% relative
		mean in g		mean in %
C	m	0.63		0.21		100.00	100.00
C	f	0.44		0.24		100.00	100.00
LD	m	0.46		0.17	*	72.61	80.28
LD	f	0.36		0.20		82.27	84.45
MD	m	0.35	*	0.12	*	56.05	57.28
MD	f	0.25	*	0.14	*	57.73	59.66
HD	m	0.26	*	0.09	*	40.61	42.72
HD	f	0.19	*	0.11	*	43.41	47.48
Testes
Group	Sex	Absolute		Relative		% absolute	% relative
		mean in g		mean in %
C	m	3.08		1.06		100.00	100.00
LD	m	3.01		1.14		97.57	107.65
MD	m	3.13		1.08		101.52	102.27
HD	m	1.78	*	0.64	*	57.56	60.53
Epididymides
Group	Sex	Absolute		Relative		% absolute	% relative
		mean in g		mean in %
C	m	0.98		0.34		100.00	100.00
LD	m	0.97		0.37		98.57	108.58
MD	m	0.92		0.32		93.99	94.38
HD	m	0.74	*	0.27	*	75.46	78.70

* significant (p<0.05); as determinded with the individual values

C: control

LD: low dose

MD: medium dose

HD: high dose

m: male

f: female

For further information on histopathological results refer to "Remarks on results including tables and figures"

Conclusions:

The test item was examined for toxicity after repeated exposure in a subacute study with rats according to OECD 407 and in compliance with GLP. Based on the treatment related findings and effects of toxicological relevance the NOAEL is therefore 150 mg/kg bw/day.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

150 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The available information comprises an adequate and reliable study, and is thus sufficient to fulfil the standard information requirements set out in Annex VIII, 8.6, of Regulation (EC) No 1907/2006.

System:

immune system

Organ:

spleen

thymus

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Repeated dose toxicity: oral route

A key repeated dose toxicity (28-day, oral) study with methyl-N-{[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) is available and was performed according to OECD TG 407 and in compliance with GLP (BSL, 2004). In this subacute toxicity study groups of five Wistar rats of each sex per dose were administered doses of 150, 500 or 1000 mg/kg bw/day or vehicle alone (corn oil) once daily for 28 consecutive days via oral gavage. Dose selection of the test material was based on a previous 14-day range finding study (BSL, 2003). Animals were observed for mortalities and clinical signs at least once a day, and detailed clinical observations were performed in the final week. Body weights, food consumption and neurobehavioural examination were recorded. Haematology parameters such as Hb, Hct, RBC, blood clotting and different leucocyte counts were evaluated. Clinical chemistry included aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, glucose, urea, creatinine, albumin, Na and K.

No mortality and no severe clinical signs of toxicity were observed throughout the study period. Food consumption and body weight development were unaffected by treatment. Hematology, urinalysis and neurobehavioural examinations revealed no effects of toxicological relevance. Clinical chemistry revealed significant differences in total protein are found for males at doses of 500 and 1000 mg/kg bw/day and females at a dose of 500 mg/kg bw/day. Hypoproteinaemia is normally observed with chronic hepatic disturbance, nephrotic disturbance or reduced protein synthesis, e.g. due to malassimilation. As the mean values of both, female and male high dose groups are less than the expected range in control animals, compound relation and dose dependency may be assumed.

The mean absolute and relative adrenals weight in the male 500 and 1000 mg/kg bw/day dose groups, as well as the mean absolute adrenals weight in the female 500 mg/kg bw/day dose group were slightly lower than the adrenals weight in the corresponding control groups, reaching statistical significance (p<0.05). This finding is assumed to be compound related, indicating a possible disturbance in the endocrine system. The mean absolute and relative thymus weight in the male and female 500 and 1000 mg/kg bw/day dose groups, as well as the mean relative thymus weight in the male 150 mg/kg bw/day dose group were reduced compared to the thymus weight in the corresponding control groups, reaching statistical significance (p<0.05). This finding is assumed to be compound related for the 500 and 1000 mg/kg bw/day dose group and was confirmed by the histopathological findings for the high dose groups. The mean absolute and relative testes and epididymides weight in the male 1000 mg/kg bw/day dose group was lower than in the control group, reaching statistical significance (p<0.05). This finding is assumed to be compound related, and was confirmed by the histopathological assessment.

Histopathology (non-neoplastic) revealed treatment-related lesions in the spleen and thymus of both sexes as well as the thyroids, epididymides and testes of male rats. Significant incidences of splenic peritonitis and thymic atrophy were limited to the 1000 mg/kg bw/day dose group. Treatment-related lesions of follicular cell hypertrophy were present in the thyroids of male rats of the 1000 mg/kg bw/day dose group. Testicular tubular degeneration and epididymal hypospermia and degenerate sperm forms (all at a minimal or mild level) were only present at the highest dosage level. The treatment-related findings were of a minor degree in each organ. There were insignificant incidences of splenic focal fibrous peritonitis, thymic atrophy and thyroid follicular cell hypertrophy in the 500 mg/kg bw/day dose group.

The decreased organ weights of the adrenals and thymus as well as histopathological evaluated lesions in the spleen, thymus, thyroid, testes and epididymides are considered treatment related findings and effects of toxicological relevance. Therefore, the NOAEL and LOAEL for males/females are considered to be 150 mg/kg bw/day and 500 mg/kg bw/day, respectively.

Justification for classification or non-classification

The available data on repeated dose toxicity of the registered substance do not meet the criteria for classification according to Regulation (EC) No 1272/2008, and are therefore conclusive but nor sufficient for classification.