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

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

Screening study for reproductive/developmental toxicity (OECD 421, oral, rat):

NOAEL systemic = 300 mg/kg bw/day

NOAEL fertility = 100 mg/kg bw/day

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-04-28 to 2016-09-27

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)

Version / remarks:

27 July 1995

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayrisches Landesamt für Gesundheit und Lebensmittelsicherheit

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Females, nulliparous and non-pregnant: yes
- Age at study initiation: 10-11 weeks old for males and females
- Weight at study initiation: Males: 265-341 g; Females: 182-204 g
- Housing: housed in groups of 2 animals / sex / cage in IVC cages (except during the mating period when one female was paired with one male and during gestation/lactation period when females were individually housed)
- Diet: Altromin 1324 maintenance diet provided ad libitum
- Water: tap water provided ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 55 ± 10
- Air changes (per hr): 10
- Photoperiod: 12 hrs dark/12 hrs light
IN-LIFE DATES: From: 2016-04-20 To: 2016-06-13

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Test formulations were prepared daily by weighing the test material in a plastic vial and adding vehicle to give the appropriate concentration. The mixture was then vortexed.

VEHICLE
- Justification for use and choice of vehicle: corn oil
- Lot/batch no.: MKBS6944V

Details on mating procedure:

- M/F ratio per cage: 1:1 (male to female)
- Length of cohabitation: Vaginal smears were checked every morning after the start of the mating period to confirm the pregnancy. If the vaginal smear was not sperm-positive, the actual stage of the estrus cycle on that day was documented.
- Proof of pregnancy: sperm in vaginal smear referred to as Day 0 of pregnancy
- No re-mating of females with a proven male was performed.
- After successful mating each pregnant female was caged individually with nesting material provided on GD 18

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Nominal concentrations were verified on study week 1 (first week of pre-mating period), 3 (first week of mating), 5 (gestation) and the last week of the study (gestation/lactation) from all groups (16 samples). Homogeneity was verified by taking samples from the top, middle and bottom of the high-dose and the low-dose formulation in study week 1 and 5.

Duration of treatment / exposure:

The animals were administered the test item formulation or vehicle 7 days per week for a period of 54 days, i.e., 14 days prior to mating, a maximum of 14 days during mating, during the gestation period and up to post-natal day 3 in females. Males were dosed after the mating period until the minimum total dosing period of 28 days was completed.

Frequency of treatment:

The test item and vehicle was administered once per day. The application volume for all groups was 5 mL/kg body weight.

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

300 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:

10 males and 10 females per dose group

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The highest dose level was selected to induce toxic effects, but not death or severe suffering. Thereafter, a descending sequence of dose levels is selected with a view to demonstrate any dose-related response and a NOAEL.
- Rationale for animal assignment: Randomization of animals was performed with IDBS Workbook 9.4.0 software.

Positive control:

None

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Prior to the start of the treatment period a detailed clinical observation outside the home cage was performed

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: At least once a day animals were observed for general health conditions, preferably at the same time each day. Morbidity and mortality were assessed twice daily except on weekends and public holidays when observations were made once daily.

BODY WEIGHT: Yes
- Time schedule for examinations: Animals were weighed once prior to group assignment, on the first day of dosing and weekly thereafter as well as at the end of the study. During pregnancy, females were weighed on gestation days (GD) 0, 7, 14 and 20 and within 24 hours of parturition (day 0 post-partum) as well as day 4 post-partum along with pups. Any animals prematurely sacrificed were weighed prior to the sacrifice.

FOOD CONSUMPTION:: Yes
- Time schedule for examinations: Food consumption was measured on the corresponding days of the body weight measurements after the beginning of the dose administration. Food consumption wasl not measured during the mating period in males and females and the post-mating period in males.

WATER CONSUMPTION AND COMPOUND INTAKE: No data

Oestrous cyclicity (parental animals):

Not examined

Sperm parameters (parental animals):

Parameters examined in male parental generations: The testes, epididymides and accessory sex organs (prostate and seminal vesicles with coagulating glands as a whole) of all male adult animals were weighed. For the testes, a detailed qualitative examination were made taking into account the tubular stages of the spermatogenic cycle at evaluation of additional hematoxylin-PAS (Periodic Acid Schiff) stained slides.

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: no; live pup were counted and sexed and litters weighed within 24 hours of parturition (day 0 post-partum) and on day 4 post-partum.

PARAMETERS EXAMINED
The following parameters were examined in F1 offspring: number and sex of pups, stillbirths, live births, runts, abnormal behavior, and the presence of gross abnormalities.

GROSS EXAMINATION OF DEAD PUPS:
yes, for gross abnormalities

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals were sacrificed after the completion of the mating period (after a minimum dosing period of 28 days)
- Maternal animals: All surviving animals were sacrificed on the respective post-natal day 4 by using an anesthesia (e.g. ketamine/xylazine). Non-pregnant females were sacrificed on study day 26 from the day of sperm-positive vaginal smear or from the last day of the mating period.

GROSS NECROPSY
- Gross necropsy consisted of an evaluation of the external surface of the body, all orifices and the cranial, thoracic and abdominal cavities and their contents.

HISTOPATHOLOGY / ORGAN WEIGHTS
The tissues indicated in Tables 1 and 2 were prepared for microscopic examination and weighed, respectively.

Postmortem examinations (offspring):

SACRIFICE
Pups were sacrificed on day 4 post-partum.

GROSS NECROPSY
- Gross necropsy consisted of an examination of the external surface of the body, all orifices and the cranial, thoracic and abdominal cavities and their contents.

HISTOPATHOLOGY / ORGAN WEIGHT
A histopathological evaluation and organ weights were not evaluated for fetuses.

Statistics:

A statistical assessment for each gender was performed by an ANOVA and a post-hoc Dunnett Test for the following parameters: body weight, food consumption, and litter data. Absolute and relative organ weights were evaluated through either a parametric one-way ANOVA and a post-hoc Dunnett Test or a non-parametric Kruskal-Wallis Test and a post-hoc Dunn's Test. Statistical analyses were performed via GraphPad Prism V.6.01 software or Ascentos 1.1.3 software (p < 0.05 being statistically significant).

Reproductive indices:

The number of implantation sites and corpora lutea were recorded for each parental female at necropsy. The fertility index was calculated as the number of pregnant females divided by the number of copulated females and multiplied by 100. The delivery index was calculated as the number of dams with live pups born divided by the number of pregnant dams and multiplied by 100.

Offspring viability indices:

The viability index was calculated as the number of live offspring at day 4 divided by the number of live offspring at birth and multiplied by 100.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Slight to moderate piloerection was observed in all high-dose males at the end of the first week of treatment. While this effect was not observed in other dose groups, the effect was transient and, therefore, not considered adverse. This effect was also observed in two high-dose females.

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

At the high dose, a statistically significant decrease in body weight (p < 0.001) was observed in males after treatment initiation. While body weight increased for males at the high dose, body weight gain remained statistically lower than the control group for the mating study period (2nd week of premating 63% below controls, p < 0.001; 1st week of mating/postmating 34% below controls, p < 0.05; 2nd week of mating/postmating 74% below controls, p < 0.001). At the end of the study, mean body weight of high-dose males was significantly lower (p < 0.001) than the controls. Low- and mid-dose males showed a body weight increase at treatment initiation; however, both dose groups exhibited a slight statistically significant decrease in total body weight gain when related to the whole treatment period. Body weight gain for low-dose males was 21% below controls (p < 0.05) and body weight gain for mid-dose males was 22% below controls (p < 0.05) for the treatment period as a whole. Decreased body weight gains observed at the low and mid dose were not considered adverse since mean body weight was not affected.

For females, a statistically significant decrease (p < 0.05) in body weight occurred during for both mid- and high-dose animals the first week of treatment. Body weight continued to be affected at the high dose, with dams exhibiting a significant decrease in body weight gain during the second and third week of gestation. No changes in mean body weight or bodyweight gain were noted for any treatment group during the lactation period. Initial body weight changes observed at the mid dose were not considered to be adverse; no significant body weight changes were observed in low-dose females.

In conclusion, body weight and body weight gain were significantly reduced in both high-dose males and females. A treatment-related effect was not observed for the mid and low-dose groups.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

In males, a decrease in food consumption was observed at the high dose during the premating period when compared to the control group (p < 0.001). A dose dependent decrease also was observed at the mid dose (p < 0.01) and low dose (no statistical significance); however, these decreases in food consumption at the mid and low dose were observed without a corresponding decrease in body weight and, therefore, were not considered treatment-related.

For females, food consumption was decreased during gestation for the high-dose group, reaching a 24% decrease when compared to the control group (p < 0.001) during the 3rd week of gestation. Only one high-dose female exhibited a decrease in food consumption during the lactation period. At the mid dose, a decrease in food consumption was observed during lactation; however, this decreased was caused by one female who showed reduced health conditions. Therefore, food consumption was not considered to be treatment-related for the mid- and low-dose groups.

In conclusion, food consumption was significantly reduced at the high dose for both males and females. A treatment-related effect was not observed for the mid and low-dose groups.

Food efficiency:

not examined

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

not specified

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

High-dose males exhibited a massive tubular degeneration associated with oligospermia or aspermia in the epididymides. High-dose males also exhibited spermatogonia in almost all tubules; however, round spermatids were rarely reported. Cellular detritus was observed in most epididymides. Mid-dose males also exhibited reproductive effects with tubular edema observed in all animals and tubular degeneration observed in 6 mid-dose males. Degeneration observed at the mid dose was caused by a loss of round and elongated spermatids in stage IV to X tubules.
Accessory male sexual glands including the prostrate, coagulation glands, and seminal vesicles were not affected.

Histopathological findings: neoplastic:

no effects observed

Other effects:

no effects observed

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

effects observed, treatment-related

Description (incidence and severity):

High-dose males exhibited a massive tubular degeneration associated with oligospermia or aspermia in the epididymides. High-dose males also exhibited spermatogonia in almost all tubules; however, round spermatids were rarely reported. Cellular detritus was observed in most epididymides. Mid-dose males also exhibited reproductive effects with tubular edema observed in all animals and tubular degeneration observed in 6 mid-dose males. Degeneration observed at the mid dose was caused by a loss of round and elongated spermatids in stage IV to X tubules.

Reproductive performance:

effects observed, treatment-related

Description (incidence and severity):

There was a slight reduction in the fertility index at the high (70%) and mid (90%) dose when compared to the control group (100%) due to the treatment-related effects on spermatogenesis. The delivery index exhibited a dose dependent decrease in the low (90%), mid (78%) and high (0%) when compared to the control group (100%); this effect was considered treatment related.

Gestation length was significantly prolonged at both the mid (23.56 days vs. 22.44 days, p < 0.001) and high dose. Prolonged gestation at the high dose was due to one dame littering at 25.00 days vs. 22.44 days in the control group. Effects observed at both dose groups were considered adverse.

There were no treatment-related effects on the number of corpora lutea or the number of implantation sites at any dose group.

Post-implantation loss was higher for all dose groups when compared to the control group (low dose: 25.14%, mid dose: 32.27%, high dose: 100%, p < 0.001, and control group: 9.45%). This increased on related to the increase in the number of still births and dams who did not liter. This effect was considered adverse.

Key result

Dose descriptor:

NOAEL

Remarks:

Systemic toxicity

Effect level:

300 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

Key result

Dose descriptor:

NOAEL

Remarks:

Reproductive toxicity

Effect level:

100 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reproductive function (sperm measures)

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

300 mg/kg bw/day (nominal)

System:

male reproductive system

Organ:

cauda epididymis

testes

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

yes

Clinical signs:

not specified

Dermal irritation (if dermal study):

not examined

Mortality / viability:

mortality observed, treatment-related

Description (incidence and severity):

The mean number of total pups (live and dead) was markedly, statistically significantly reduced at the high dose (0.29 compared to 10.50 pups in the control group), p<0.001) due to adverse effects of the test material. The mean number of still births also was dose-dependently higher in the low- (2.4) and mid-dose (3.11) groups when compared to the control group (0.10). While the increases in still births did not reach statistical significance for either the low- or mid-dose groups, the increases observed were above historical control data and considered treatment related. A moderate increase in mortality of 22.46% (p<0.05) was observed at the mid dose that reached statistical significance. This increase was related to pups found dead or missing (attributed to cannibalism by a dam) solely on post-natal days 1 and 2. No increases in mortality occurred on post-natal days 3 and 4. Furthermore, there was a statistically relevant effect of the test item on number of live pups born which were dose dependently reduced throughout low-dose (8.20), mid-dose (7.11) and high-dose group (0.00) when compared to the control group (10.40). Though this effect did not reach statistical significance except for the high-dose group, this was considered biologically relevant and an adverse effect for all dose groups.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Litter weight was marginally lower on postnatal day 0 at the low (6.06 g) and mid (5.56 g) dose when compared to the control group (6.36 g); these decreases did not reach statistical significance. The decrease observed at the low dose was not considered treatment-related because the difference between the low dose and the control group was 5%. Decreases at 300 mg/kg/day were considered treatment related because a moderate decrease (27% below controls, p <0.05) was also observed on postnatal day 4. Because the high dose did not litter any pups, litter weight could not be evaluated.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

no effects observed

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

In one litter, 11/12 low-dose pups exhibited milk barely visible on postnatal day 0. This effect was also observed in a few mid-dose pups. Mid-dose pups in one litter were noted to be slightly cold and dead or missing within the next two days. One other litter in the mid-dose group was observed with slightly dry and scaly skin on postnatal day 4. Other external findings of dead pup in any of the dose groups included damaged tissues, discolored skin, squashed bodies, and missing body parts due to cannibalism by the dam. Some still born pups fro the low- and mid-dose groups were noted to have the placenta still attached to their bodies. None of these findings were considered treatment-related or adverse.

Histopathological findings:

not examined

Other effects:

not specified

Behaviour (functional findings):

not examined

Developmental immunotoxicity:

not examined

Key result

Dose descriptor:

LOAEL

Generation:

F1

Effect level:

100 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

viability

mortality

Key result

Reproductive effects observed:

yes

Lowest effective dose / conc.:

100 mg/kg bw/day (nominal)

Treatment related:

yes

Relation to other toxic effects:

reproductive effects in the absence of other toxic effects

Dose response relationship:

yes

Relevant for humans:

yes

TABLE 3. Mean body weight and body weight gain

	Observations/study week		Dose group (mg/kg/day)
			0		100		300		1000
PGeneration Males
Mean body weight (g)
Premating - Day 1		314.70±19.54		316.10±17.95		311.70±16.97		314.80±19.00
Premating - Day 7		330.40±22.28		327.40±19.87		322.60±22.10		314.20±19.58
Premating - Day 14		351.30±23.57		344.70±20.89		340.60±27.14		321.90±20.79*
Mating/Postmating - Day 7		368.00±25.88		360.10±20.05		354.90±25.23		333.00±22.44**
Mating/Postmating - Day 14		387.00±29.67		372.90±20.06		367.90±26.01		338.00±24.62***
Terminal Sacrifice		393.80±31.87		377.30±21.09		370.90±26.57		340.30±24.06***
Mean body weight change (g)
Premating - Days 1-7		15.70±7.23		11.30±4.69		10.90±7.87		-0.60±6.82***
Premating - Days 7-14		20.90±4.12		17.30±3.74		18.00±7.87		7.70±4.14***
Premating Day 14 – Mating/Postmating Day 7		16.70±6.96		15.40±4.33		14.30±4.06		11.10±2.73*
Mating/Postmating Day 7 – Mating/Postmating Day 14		19.00±6.93		12.80±5.07		13.00±5.21		5.00±5.87***
Premating Day 1 – Postmating Day 14		72.20±17.59		56.80±6.88		56.20±11.20*		23.20±10.51***
Premating Day 1 – Terminal Sacrifice		79.10±17.97		61.20±7.83**		59.20±12.06**		25.50±10.78***
PGeneration Females
Mean body weight (g)
Day 1		194.60±4.93		195.00±8.21		199.00±7.23		202.60±8.76
Day 7		199.70±6.91		200.70±8.30		796.20±7.83		200.60±7.50
Day 14		206.10±5.99		206.60±10.01		205.80±10.65		204.50±8.53
Mean body weight change (g)
Days 1-7		5.10±6.40		5.70±2.21		-2.80±5.92*		-2.00±7.33*
Days 7-14		6.40±3.81		5.90±3.98		9.60±7.40		3.90±4.98
Gestational body weight (g)
Day 0		205.44±6.73		207.70±7.45		207.56±11.81		206.71±7.70
Day 7		229.44±7.57		225.80±8.65		228.78±13.92		227.14±7.29
Day 14		255.89±6.33		252.70±9.92		248.00±11.57		240.29±14.43*
Day 20		312.22±11.20		309.00±1051		204.22±21.03		251.86±32.70***
Gestational body weight changes (g)
Days 0-7		24.00±4.69		18.10±3.28		21.22±6.44		20.43±3.60
Days 7-14		26.44±5.46		26.90±2.96		19.22±8.20		13.14±±9.97**
Days 14-20		56.33±8.03		56.30±4.14		56.22±13.07		11.57±19.16***
Days0-20		106.78±9.02		101.30±5.50		96.67±14.87		45.14±30.29***
Lactational body weights (g)
Day 0		238.20±11.12		229.70±17.40		223.78±7.21		242.00±---
Day 4		239.70±8.99		229.40±18.09		224.22±21.88		237.00±---
Lactational body weight changes (g)
Days 0-4		1.50±14.79		-0.30±13.65		0.44±18.60		-5.00±---

* Statistically different from control,p<0.05.

** Statistically different from control,p<0.01.

*** Statistically different from control,p<0.001.

 

TABLE 4. Mean food consumption

	Observations/study week	Dose group (mg/kg/day)
		0	100	300		1000
PGeneration Males
Food Consumption (g)
Premating - Days 1-7		270.40±15.96	249.80±8.04	244.00±9.22*	219.20±17.66**
Premating - Days 7-14		310.80±24.26	284.80±8.23	274.00±15.62**	249.20±16.53***
PGeneration Females
Food consumption (g)
Days 1-7		15.40±10.50	161.60±6.50	153.20±7.89	154.80±8.11
Days 7-14		183.00±10.20	179.40±5.90	172.00±12.75	173.60±9.45
Gestational food consumption (g)
Days 0-7		110.89±12.38	102.10±7.13	105.56±13.97	107.14±5.34
Days 7-14		117.33±10.07	112.50±8.71	108.63±17.05	98.86±18.60
Days 14-20		115.67±5.07	114.80±6.60	102.75±13.65	87.71±20.77***
Lactational food consumption (g)
Days 0-4		85.30±11.55	67.30±24.27	56.44±29.85*	30.00±---

* Statistically different from control,p<0.05.

** Statistically different from control,p<0.01.

*** Statistically different from control,p<0.001.

 

 

TABLE 5. Reproductive performance in the P generation

Observation	Dose group (mg/kg/day)
	Control	100	300	1000
FEMALES
Number mated	10	10	10	10
Number with evidence of copulation	9	10	10	10
Number achieving pregnancy	10	10	9	7
Precoital interval	2.56±0.88	2.90±0.88	1.90±0.99	2.00±1.63
Gestation duration (days)	22.44±0.53	22.70±0.48	23.56±0.53***	25.00±---
Number of dams with live young born	10	9	7	0
Fertility index	100%	100%	90%	70%
Preimplantation loss	12.72±22.24	10.18±9.81	9.93±7.62	12.84±13.43
Postimplantation loss	9.45±13.08	25.14±34.99	37.27±37.90	100.00±0.00***
Delivery index^a	100%	90%	70%	0%

*** Statistically different from control,p<0.001.

a: Dose-dependent decrease observed

 

TABLE 6. Selected absolute (g) and relative organ weights (g/100 g)

Observation	Dose group (mg/kg/day)
	Control	100	300	1000
P Generation
MALES
Testes (absolute)	3.5291±0.2713	3.6915±0.3422	3.4376±0.3172	1.4991±0.1920***
Testes (relative)	0.9029±0.112	0.9800±0.0943	0.9277±0.712	0.4419±0.0594***
Epididymides (absolute)	1.4011±0.0943	1.4317±0.1376	1.3395±0.0949	0.8500±0.0740***
Epididymides (relative)	0.3587±0.0446	0.3795±0.0297	0.3620±0.0251	0.2506±0.0236***
Prostate (absolute)	2.8641±0.8606	2.4777±0.2724	2.2856±0.4686	1.9158±0.2410***
Prostate (relative)	0.7352±0.2353	0.6496±0.0666	0.6156±0.1293	0.5664±0.0879
Thymus (absolute)	0.5586±0.0909	0.5556±0.1153	0.3434±0.0662***	0.3027±0.1087***
Thymus (relative)	0.1420±0.0209	0.1471±0.0288	0.0937±0.0158***	0.0891±0.0310***
Spleen (absolute)	0.8813±0.1627	0.8346±0.1189	0.7418±0.0756*	0.7142±0.1067**
Spleen (relative)	0.224±0.0395	0.2215±0.0324	0.2009±0.0245	0.2095±0.0237
FEMALES
Uterine (absolute)	0.672±0.0698	0.7704±0.1061	0.7494±0.0998	1.8336±1.3025**
Uterine (relative)	0.2808±0.0318	0.3382±0.0572	0.3385±0.0664	0.7632±0.5118***
Thymus (absolute)	0.2029±0.0320	0.1805±0.0169	0.1663±0.0656	0.1331±0.0383*
Thymus (relative)	0.0846±0.0126	0.0782±0.0141	0.0741±0.0288	0.0564±0.0132*
Spleen (absolute)	0.7136±0.0948	0.6533±0.1590	0.6453±0.1751	0.5289±0.0866*
Spleen (relative)	0.2975±0.0346	0.2831±0.0564	0.2865±0.0625	0.2262±0.0337**

* Statistically different from control,p<0.05.

** Statistically different from control,p<0.01.

*** Statistically different from control,p<0.001.

 

TABLE 7. Selected microscopic effects

Observation	Dose group (mg/kg/day)
	Control	100	300	1000
P Generation Males
Testes
Tubular edema	0	0	10/10	0
Tubular degeneration	1/10	0	6/10	10/10
Epididymides
Aspermia	0	0	0	2/10
Oligospermia	0	0	0	8/10
Cellular detritus	0	0	2/10	7/10

 

TABLE 8. Litter parameters for F₁generation

Observation	Dose group (mg/kg/day)
	Control		100	300	1000
F1Generation
Mean implantation sites		11.70±3.27	11.10±1.37	11.78±1.09	11.57±2.07
Total number born (live + dead)		10.50±2.51	10.60±1.43	10.22±1.64	0.29±0.76***
Number of male (live + dead)		5.50±2.46	5.20±1.87	5.22±1.39	0.14±0.38***
Number of female (live + dead)		5.00±1.89	5.40±1.65	4.89±1.54	0.00±0.00***
Sex ratio (males/females)		1.41±1.24	1.13±0.67	1.27±0.080	---
PND 0
Mean number live		10.40±2.63	8.20±3.91	7.11±4.23	0.00±0.00***
Still birth		0.10±0.32	2.40±4.38	3.11±4.94	0.29±0.76

*** Statistically different from control,p<0.001.

TABLE 16. Mean (±SD) pup and litter weights (g)

PND	Dose group (mg/kg/day)
	Control	100	300	1000
F1Pups
0	6.36±0.77	6.06±0.73	5.56±0.44	---
4	10.50±1.70	9.92±1.19	9.09±0.54	---
F1Litters
0	64.71±11.75	55.54±17.33	50.89±9.33	---
4	105.39±13.90	89.08±24.51	77.33±19.16*	---

* Statistically different from control,p<0.05.

Conclusions:

A screening for reproductive/developmental toxicity was performed with the test substance according to OECD TG 421 and GLP at dose levels of 100, 300 and 1000 mg/kg bw/day. The NOAEL for general systemic toxicity (apart from the observed effects on male reproductive organs) can be established at 300 mg/kg bw/day based on adversely reduced body weight and food consumption at the highest dose level. The NOAEL for fertility is 100 mg/kg bw/day as indicated by effects on spermatogenesis at the mid and high dose levels. A NOAEL for developmental toxicity could not be established due to increased number of still births at all tested dose levels.

Effect on fertility: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

100 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, 8.7, of Regulation (EC) No 1907/2006.

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

A key screening for reproductive/developmental toxicity (oral) study with methyl-N-{[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) is available and was performed according to OECD TG 421 and in compliance with GLP (Eurofins, 2015). The test substance was administered daily in graduate doses (100, 300, and 1000 mg/kg bw/day) to 3 groups of test animals per gavage, one dose level per group for a treatment period of up to 54 days, i.e. during 14 days of pre-mating and maximum 14 days of mating in both males and females, during gestation period and up to post-natal day 3 in females. Males were dosed after the mating period until the minimum total dosing period of 28 days was completed. Animals in additional control group were handled identically as the dose groups but received corn oil, the vehicle used in this study. The 4 groups consisted of 10 male and 10 female Wistar rats.

No mortality of adult animals occurred in the control or any of the dose groups during the treatment period of this study. At a dose level of 1000 mg/kg bw/day significantly reduced body weight and food consumption were noted in males and females. Duration of gestation was dose dependently prolonged at 300 and 1000 mg/kg bw/day. The delivery index (no of dams with live pups born / no. of pregnant dams x 100) was noted to be dose dependently reduced at 100 (90%), 300 (78%) and 1000 mg/kg bw/day (0%) when compared to 100% in the control group. Further, test substance-related, adverse effects were observed for litter data. The mean number of total pups delivered (live and dead) was markedly reduced at 1000 mg/kg w/day (0.29 compared to 10.5 pups in the control group). Testes and epididymides were recorded to be of a small size in all males dosed with 1000 mg/kg bw/day which was associated with a markedly reduced testes weight and epididymides weight. Histopathological, this was correlated to test substance induced effects on the spermatogenesis. At 300 mg/kg bw/day tubular edema with tubular degeneration due to loss of round and elongated spermatids in stage IV to X tubules was observed. At 1000 mg/kg bw/day a massive tubular degeneration associated with oligospermia or aspermia in the epididymides was noted.

The NOAEL for effects on fertility is 100 mg/kg bw/day as indicated by effects on spermatogenesis at the higher tested dose levels.

Under the conditions of this reproductive/developmental toxicity screening test, apart from the observed effects on male reproductive organs, the NOAEL for general systemic toxicity can be established at 300 mg/kg bw/day based on adversely reduced body weight and food consumption at the highest dose level evaluated.

Effects on developmental toxicity

Description of key information

Screening study for reproductive/developmental toxicity (OECD 421, oral, rat):

NOAEL systemic = 300 mg/kg bw/day

LOAEL developmental = 100 mg/kg bw/day (no NOAEL could be established because adverse effects were observed up to lowest dose tested)

Effect on developmental toxicity: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LOAEL

100 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, 8.7, of Regulation (EC) No 1907/2006.

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

A key screening for reproductive/developmental toxicity (oral) study with methyl-N-{[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) is available and was performed according to OECD TG 421 and in compliance with GLP (Eurofins, 2015). The test substance was administered daily in graduate doses (100, 300, and 1000 mg/kg bw/day) to 3 groups of test animals per gavage, one dose level per group for a treatment period of up to 54 days, i.e. during 14 days of pre-mating and maximum 14 days of mating in both males and females, during gestation period and up to post-natal day 3 in females. Males were dosed after the mating period until the minimum total dosing period of 28 days was completed. Animals in additional control group were handled identically as the dose groups but received corn oil, the vehicle used in this study. The 4 groups consisted of 10 male and 10 female Wistar rats.

No mortality of adult animals occurred in the control or any of the dose groups during the treatment period of this study. At a dose level of 1000 mg/kg bw/day significantly reduced body weight and food consumption were noted in males and females. Duration of gestation was dose dependently prolonged at 300 and 1000 mg/kg bw/day. The delivery index (no of dams with live pups born / no. of pregnant dams x 100) was noted to be dose dependently reduced at 100 (90%), 300 (78%) and 1000 mg/kg bw/day (0%) when compared to 100% in the control group. Further, test substance-related, adverse effects were observed for litter data. The mean number of total pups delivered (live and dead) was markedly reduced at 1000 mg/kg w/day (0.29 compared to 10.5 pups in the control group). There was an adverse effect of the test substance on number of live pups born which were dose dependently reduced throughout all dose groups (8.20, 7.11 and 0.00 at doses of 100, 300, and 1000 mg/kg bw/day, respectively, when compared to 10.4 pups in controls). The mean number of still births was also dose dependently higher at 100 mg/kg bw/day (2.4) and 300 mg/kg bw/day (3.11) when compared to the control group (0.1). Thus, there was a dose dependently increase post-implantation loss in the dose groups. At a dose level of 300 mg/kg bw/day mean pup weight was slightly below controls. The viability index was also reduced (77.54% compared to 100% in controls) due to increased death of pups on post-natal day 1 and/or 2.

Thus, based on the developmental effects (mortality/viability of off-springs) at all tested dose levels of 100, 300, and 1000 mg/kg bw/day, no NOAEL for developmental toxicity can be established. Under the conditions of this reproductive/developmental toxicity screening test, the NOAEL for general systemic toxicity can be established at 300 mg/kg bw/day based on adversely reduced body weight and food consumption at the highest dose level evaluated.

Justification for classification or non-classification

Based on the developmental effects (death of the developing organism) and effects on male reproductive organs incl. spermatogenesis, the substance meet the criteria for classification as Repr. 2 (H361fd).