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Key value for chemical safety assessment

Effects on fertility

Description of key information

A study according to OECD 421 ("Reproduction/Developmental Toxicity Screening Test") was conducted to assess the possible effects of 1,1 -Dimethylurea on male and female fertility and embryofetal development after repeated dose administration in Wistar rats.

The test item was administered daily in graduated doses to 3 groups of test animals, 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 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. Animals of an additional control group were handled identically as the dose groups but received aqua ad injectionem, the vehicle used in this study. The 4 groups comprised 10 male and 10 femaleWistarrats.

The following doses were evaluated:

Control:                        0         mg/kg body weight/day

Low Dose:                    100     mg/kg body weight/day

Medium Dose:              300     mg/kg body weight/day

High Dose:                   1000   mg/kg body weight/day

On the basis of this reproduction/ developmental toxicity screening test with1,1-Dimethylureain male and femaleWistarrats with dose levels of 100, 300, and 1000 mg/kg body weight/day the following conclusions can be made:

There were no toxicologically relevant clinical signs at any dose level tested.

At a dose level of 1000 mg/kg body weight/day toxicologically relevant, adverse effects on body weight and/or body weight gain were noted in males and females. Food consumption was also adversely effected in females at the same dose level.

Test item related, adverse effects were observed for litter data. A lower number of male pups born was evident at 1000 mg/kg body weight/day as well as a tendency towards lower mean number of total pups delivered. The mean number of live pups on post-natal day 4 was also moderately reduced at 1000 mg/kg body weight/day due to reduced survivability of pups of both genders. Increased mortality of 7.85 % was noted at 1000 mg/kg body weight/day based on death of pups on post-natal day 1 and 2. Mean pup weight on post-natal day 0 as well as total litter weight on post-natal day 0 and day 4 was adversely reduced at 1000 mg/kg body weight/day. Furthermore, there was a slight tendency towards lower mean number of corpora lutea and implantation sites and slightly higher post-implantation loss at 1000 mg/kg body weight/day for which a relation to the treatment with the test item cannot be excluded.

1,1-Dimethylurea produced no morphological evidence of toxicological properties in the reproductive organs and tissues examined histopathologically.

Link to relevant study records
Reference
Endpoint:
screening for reproductive / developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
11.05.2016 - 20.12.2016
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)
GLP compliance:
yes (incl. QA statement)
Limit test:
no
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: AlzChem AG / Lot No 534201
- Expiration date of the lot/batch: 31.12.2017
- Purity test date: 17.12.2015

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature
- Stability under test conditions: stable
- Solubility and stability of the test substance in the solvent/vehicle: solubility in water 143.7 g/L at 20 °C / stable for 10 days

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: approx. 10-11 weeks
- Weight at study initiation: Males: 272- 323 g; Females: 181 - 216 g
- Housing: - The animals were kept in groups of 2 animals / sex / cage in IVC cages (type III H, polysulphone cages) on Altromin saw fibre bedding) (lot no. 02102151120) (except during the mating period when one female was paired with one male and during gestation/lactation period when females were housed individually)
- Diet (e.g. ad libitum): Free access to Altromin 1324 maintenance diet for rats and mice (lot no. 0922)
- Water (e.g. ad libitum): - Free access to tap water, sulphur acidified to a pH of approximately 2.8 (drinking water, municipal residue control, microbiological controls at regular intervals)
- Acclimation period: 7 days
ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3°C
- Humidity (%): 55+/-10 %
- Air changes (per hr): 10 x/ hour
- Photoperiod (hrs dark / hrs light): Artificial light, sequnce beeing 12 hours light, 12 hours dark

IN-LIFE DATES: From: To:
Acclimatisation Period: 12 May 2016 till 19 May 2016
Experimental Starting Date: 20 May 2016
Treatment Period: 20 May 2016 till 16 June 2016 (males) / 20 April 2016 till 10 July 2016 (females)

Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
The test item formulation was prepared with aqua ad injectionem. The vehicle was selected based on the test item’s characteristics and testing guideline.
The test item was weighed into a tared plastic vial on a suitable precision balance and the vehicle was added to give the appropriate final concentration of the test item. The formulation was further vortexed until a clear solution was obtained.
The test item formulation was prepared at least once every 10 days based on available stability data (Eurofins Munich study no. 157748). The prepared formulation was stored at room temperature.
Formulates were kept under magnetic stirring until the end of the daily administration.
The vehicle was also be used as control item.


VEHICLE
- vehicle: aqua ad injectionem
- Amount of vehicle (if gavage): The test item and vehicle were administered at a single dose to the animals by oral gavage. The application volume for all groups was 10 mL/kg body weight. For each animal the individual dosing volume was calculated on the basis of the body weight most recently measured.
- Lot/batch no. (if required): 511535
Details on mating procedure:
Mating was performed using a ratio of 1:1 (male to female). The vaginal smear of the females was checked every morning after the start of the mating period to confirm the pregnancy. If the vaginal smear of a particular female was not found to be sperm-positive, the actual stage of the estrus cycle on that day was documented. The day of the vaginal plug and/or sperm was considered as day 0 of gestation.
The cages were arranged in such a way that possible effects due to cage placement were minimised. No re-mating of females with proven males was performed.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Concentration analysis of formulation samples was made for all groups in study weeks 1, 3, 5 and in the last study week. The mean recoveries observed in the LD, the MD and the HD group were 101.9 %, 102.1 % and 101.0 % of the nominal concentration, respectively. Nominal concentrations were confirmed for all single samples as measured concentrations were within acceptance criterion of 10 %.
Homogeneity of formulation samples was determined for the LD and the HD group in study weeks 1 and 5. The mean recoveries observed for the LD group were 100.8 % and 101.8 % of the nominal value and 99.2 % and 102.6 % of the nominal value for the HD group. The coefficients of variation of the different sampling locations (top, middle, bottom) were 0.2 % and 0.6 % in the LD group, 0.8 % and 2.3 % in the HD group. All samples were homogenous, as COV was below or equal 10%.
Duration of treatment / exposure:
The animals were treated with the test item formulation or vehicle on 7 days per week for a period of 54 days, i.e. during 14 days of pre-mating and maximum 14 days of mating in both males and females, 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:
daily
Dose / conc.:
0 mg/kg bw/day
Remarks:
Control Group
Dose / conc.:
100 mg/kg bw/day
Remarks:
Low Dose Group
Dose / conc.:
300 mg/kg bw/day
Remarks:
Medium Dose Group
Dose / conc.:
1 000 mg/kg bw/day
Remarks:
High Dose Group
No. of animals per sex per dose:
80 animals (40 males and 40 females) were included in the study (10 male and 10 female animals per group).
Control animals:
yes, concurrent vehicle
Details on study design:
According to the results of a previous dose range finding study (BSL Munich study no. 157744, non-GLP) and in consultation with the sponsor the doses 0, 100, 300 and 1000 mg/kg bw/d were selected for the 3 dose groups (LD = low dose, MD = medium dose, HD = high dose).
In the dose range finding study for the reproductive / developmental toxicity screening test with 3 male and 3 female animals per group at dose levels of 100, 300 and 1000 mg/kg body weight/day no mortality and no clinical signs of toxicological relevance were observed up to the highest dose level tested. At 1000 mg/kg body weight/day slight test item related effects on body weight and food consumption were observed. Dose-dependently moderately lower mean weight of pups was noted on post-natal day 0 and day 4 at 300 and 1000 mg/kg body weight/day. Furthermore, marginally lower survival of pups was revealed at 1000 mg/kg body weight/day. Based on the data generated, the same dose levels were selected for the present main study.
The animals were treated with the test item formulation or vehicle on 7 days per week for a period of 54 days, i.e. during 14 days of pre-mating and maximum 14 days of mating in both males and females, 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.
The highest dose level was chosen with the aim of inducing toxic effects, but no death or severe suffering. Thereafter, a descending sequence of dose levels was selected with a view to demonstrate any dosage related response and NOAEL.
The animals in the control group were handled in an identical manner to the test group subjects and received aqua ad injectionem using the same volume as used for the dose groups.
Positive control:
no
Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes
General clinical observations were made at least once a day, preferably at the same time each day. The health condition of the animals was recorded. Twice daily all animals were observed for morbidity and mortality except on weekends and public holidays when observations were made once daily.

DETAILED CLINICAL OBSERVATIONS: Yes
Observations for clinical signs included the check for spontaneous activity, lethargy, recumbent position, convulsions, tremors, apnoea, asphyxia, vocalisation, diarrhoea, changes in the skin and fur, eyes and mucous membranes (salivation, discharge), piloerection and pupil size. Any changes in gait, posture, response to handling as well as the presence of clonic or tonic movements, stereotypes, difficult or prolonged parturition or bizarre behaviour were recorded if present.

BODY WEIGHT: Yes
The animals were weighed once before the assignment to the experimental groups, 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 on day 4 post-partum along with pups.
Food consumption was measured on the corresponding days of the body weight measurements after the beginning of the dose administration. Food consumption was not measured during the mating period in males and females and the post-mating period in males.
Litter observations:
The duration of gestation was recorded and was calculated from day 0 of the pregnancy. Each litter was examined as soon as possible after delivery of the dam to establish the number and sex of pups, stillbirths, live births, runts and the presence of gross abnormalities.
Live pups were counted and sexed and litters weighed within 24 hours of parturition (day 0 post-partum) and on day 4 post-partum. Live pups were identified by tattoo marks on paws and tail. In addition to the observations of the parent animals, any abnormal behaviour of the offspring was recorded.
Postmortem examinations (parental animals):
SACRIFICE
All males were sacrificed after the completion of the mating period (total dosing period: 28 days) on study day 29 and females were sacrificed on the respective post-natal day 4 by using anaesthesia (ketamine/xylazine, 2:1).
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
All animals were subjected to a detailed gross necropsy which includes careful examination of the external surface of the body, all orifices and the cranial, thoracic and abdominal cavities and their contents.
Special attention was paid to the organs of the reproductive system.

ORGAN WEIGHTS
The testes, epididymides and accessory sex organs (prostate and seminal vesicles with coagulating glands as a whole) of all male adult animals as well as the ovaries and uterus with cervix of all female adult animals were weighed.
Paired organs were weighed together. Organ weights of one animal found dead were not taken.

HISTOPATHOLOGY
A full histopathology was carried out on the preserved organs and tissues of one animal which died during the study.
Testes, epididymides, ovaries, oviducts, uterus with cervix, vagina, accessory sex organs (prostate and seminal vesicles with coagulating glands) were trimmed, embedded into paraffin, cut at an approximated thickness of 2-4 µm and stained with hematoxylin and eosin and examined in control and HD animals and in non-pregnant female animals of the MD group. Testes, epididymides and accessory sex organs (prostate, seminal vesicle with coagulating gland) were also examined in the mating partners of the non-pregnant female MD animals.
Any gross lesion macroscopically identified was examined microscopically in all animals.
For the testes, a detailed qualitative examination was made, taking into account the tubular stages of the spermatogenic cycle at evaluation of additional hematoxylin-PAS (Periodic Acid Schiff) stained slides.
The histological processing of tissues to microscope slides was performed at the GLP-certified contract laboratory AnaPath GmbH, AnaPath Services, Hammerstr. 49, 4410 Liestal, Switzerland (test site for tissue processing). The histopathological evaluation was performed at the GLP-certified contract laboratory AnaPath GmbH, Buchsweg 56, 4625 Oberbuchsiten, Switzerland (test site for histopathology). The study phases from test site 1 and 2 were performed in compliance with the Swiss Ordinance relating to Good Laboratory Practice adopted 18 May 2005 [SR 813.112.1] (Status as of 01 December 2012). Blocking, embedding, cutting, H&E staining and scientific slide evaluation was performed according to the corresponding SOP’s of the test sites.



Postmortem examinations (offspring):
Dead pups and all surviving pups on PND 4 were carefully examined externally for gross abnormalities.
Statistics:
A statistical assessment of the results of the body weight, food consumption and litter data were performed for each gender by comparing values of dosed with control animals of the main groups using a one-way ANOVA and a post-hoc Dunnett Test. Parameters of absolute and relative organ weights were statistically analyzed by comparing values of dosed with control animals using 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, based on the results of homogeneity and normality tests. These statistics were performed with GraphPad Prism V.6.01 software or Ascentos 1.1.3 software (p<0.05 was considered as statistically significant).
Reproductive indices:
Copulation index: Number of animals copulated / no. of pairs x 100
Fertility index: Number of pregnent females / number of copulated females x 100
Delivery index: Number of dams with live pups born / number of pregnant dams x 100
Offspring viability indices:
Viability index: number of live offspring at day 4 / number of live offspring at birth x 100
Clinical signs:
no effects observed
Mortality:
mortality observed, non-treatment-related
Description (incidence):
One male of the HD group was found dead on day 3 after start of treatment. At necropsy the lung was discoloured dark and did not collapse. Along with the histopathological finding of foaming cytoplasm in alveolar macrophages around the terminal bronchioles, the cause of this single sudden death without preceding signs of toxicity was likely considered as gavaging error or accidental inhalation of the test item.
With this exception, all animals survived the treatment period.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
In both males and females, the mean body weight increased with the progress of the study in the dose groups and the control group.
However, in males, mean body weight gain of the HD group was moderately and statistically significantly lower in the premating period when compared to controls (p < 0.001 in the first week, p < 0.05 in the second week). This resulted in a markedly reduced mean body weight gain when related to the whole treatment period (58 % of controls, p < 0.001) which also affected the mean body weight. Mean body weight of the male HD group was marginally lower from the end of the premating period (94 % of controls) until terminal sacrifice (92 % of controls) but narrowly missed statistical significance.
Slightly lower mean body weight gain was also noted in the first week of premating in the male MD group when compared to controls (p < 0.05). However, as this slight and transient difference had no statistically or biologically significant impact on mean body weight of the MD group, it was not considered as adverse.
In females, slightly to moderately lower body weight gain was observed in the HD group during the whole treatment period compared to controls with reaching statistical significance in the second week of premating (p < 0.05) and second (p < 0.01) and third week of gestation (p < 0.005). When related to the whole gestation period, body weight gain of the HD group was 69 % of controls (p < 0.005). Thus, mean body weight of the female HD group was slightly and statistically significantly reduced on day 7 of gestation (94 % of controls, p < 0.01), on day 14 of gestation (91 % of controls, p < 0.01) and moderately reduced on day 20 of gestation (87 % of controls, p < 0.001). Mean body weight was also slightly lower on day 4 of lactation (94 % of controls, p < 0.05).
No effects of toxicological relevance were noted in the other dose groups.
Food efficiency:
no effects observed
Description (incidence and severity):
There was no effect of toxicological relevance on food consumption during the premating period of males of any of the groups.
However, in accordance to the attenuated body weight gain during gestation, food consumption of the female HD group was noted to be moderately lower when compared to the control group (second week of gestation 84 % of controls, p < 0.001; third week of gestation 83 % of controls, p < 0.001). Food consumption remained moderately lower in the lactation period (75 % of controls, p < 0.01).
No considerable effect on food consumption was noted for the female LD and MD group.
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
effects observed, non-treatment-related
Histopathological findings: non-neoplastic:
effects observed, non-treatment-related
Description (incidence and severity):
One male of the HD group was found dead on day 3 after start of treatment. The exact cause of its death could not be established from the organs and tissues examined. However, alveolar macrophages containing foaming cytoplasm were recorded at slight degree mainly around the terminal bronchioles of the lung. This finding may be indicative for accidental inhalation of the test item in the lung, however, no foreign body material could be detected in the sections examined.
The cause of the non-pregnancy of female no. 62, 64 and 70 of the MD group could not be established from the tissues and organs examined from these animals and from their male pairing partners.
All other findings recorded were within the range of normal background lesions which may be recorded in animals of this strain and age and in this study type
Key result
Dose descriptor:
NOAEL
Effect level:
300 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
body weight and weight gain
Critical effects observed:
no
Clinical signs:
no effects observed
Mortality / viability:
mortality observed, treatment-related
Description (incidence and severity):
All live pups of the control and the LD group survived from post-natal day 0 to 4.
A marginally reduced survivability in the MD group was related to the death of one single female pup on post-natal day 1 which was considered as incidental.
However, reduced survivability in the HD group with a total mortality of 7.85 % compared to 0.00 % in controls was considered as an adverse effect of the treatment with the test item (p < 0.01) This was related to pups of both genders found dead or missing (attributed to cannibalism by the dam) solely on post-natal day 1 and 2. No mortality occurred on day 3 and 4.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Slightly and statistically significantly lower mean pup weight was noted in the HD group on post-natal day 0 when compared to the control group (5.28 g compared to 6.08 g in the control group, p < 0.05). There was also a tendency towards lower mean pup weight in the HD group on post-natal day 4 but without reaching statistical significance (8.93 g compared to 10.03 g). Based on the reduced pup weight and number of pups, total litter weight and male litter weight were markedly lower in the HD group on post-natal day 0 and day 4 when compared to the control group (each p < 0.001). Total litter weight of the HD group was 62 % of controls on day 0 and 59 % of controls on day 4.
No statistically or biologically significant difference was noted for litter weight data of the MD and the LD group when compared to the control group.
Gross pathological findings:
effects observed, non-treatment-related
Description (incidence and severity):
There were no external abnormalities of toxicological relevance in any of the pups of the control, the LD and the MD group.
The one pup of the HD group which was still born was observed with malformations of the head (flat snout, flat skull and long tongue). As this was a single case, it could be considered as incidental. Another pup of the HD group was noted to be pale and cold with a dark abdomen on the day of birth and was missing on the next day. There were no other external abnormalities in pups except for damaged tissues (crushed/squashed bodies) of dead pups due to the dam.
Key result
Dose descriptor:
NOAEL
Generation:
F1
Effect level:
300 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
viability
mortality
body weight and weight gain
Critical effects observed:
no
Key result
Reproductive effects observed:
yes
Lowest effective dose / conc.:
1 000 mg/kg bw/day
Treatment related:
yes
Relation to other toxic effects:
reproductive effects in the absence of other toxic effects
Dose response relationship:
yes
Relevant for humans:
not specified

Precoital Interval and Duration of Gestation

Length of precoital interval and duration of gestation were within the normal range of variation for animals of this age and strain in the dose groups and the control group. There was no statistically significant effect. Successful mating resulted in 10/10 pregnancies in the control, the LD and the HD group and 7/10 pregnancies in the MD group which was considered as incidental in nature.

Pre- and Post-Natal Data

In the HD group, there was a tendency towards lower mean number of corpora lutea (9.60) and implantation sites (9.00) when compared to the control group (11.60 and 11.30, respectively). Though not reaching statistical significance, a relation to the treatment with the test item cannot be excluded. No such effect was seen in the MD and the LD group.

There was no effect of toxicological relevance on percentage of pre-implantation loss. Values were within the normal range of variation.

There were no statistically significant effects on percentage of post-implantation loss. Marginally higher post-implantation loss in the LD group (16.16 %) compared to 4.15 % in the control group was seen without dose dependency and was mainly related to a 100 % loss in female no. 52 which was not observed littering but had an implantation site at necropsy. This was considered incidental. Furthermore, there was a slight but not statistically significant tendency towards higher post-implantation loss in the HD group (14.42 %) due to losses in 8/10 females including one still birth. A relation to the treatment with the test item cannot be excluded.

Reproductive Indices

The copulation index (no. of animals copulated/no. of pairs x 100) was 100 % in all groups including control.

The fertility index (number of pregnant females/number of copulated females x 100) was slightly lower in the MD group (70 %) compared to 100 % in the control, the LD and the MD group.The cause of the non-pregnancy of female no. 62, 64 and 70 of the MD group could not be established from the tissues and organs histopathologically examined from these animals nor from their male pairing partners. Without dose dependency, this was considered as incidental in nature.

The delivery index (no. of dams with live pups born / no. of pregnant dams x 100) wasslightly lower in the LD group (90 %) compared to 100 % in the control group, the MD and the HD group.Without dose dependency, this was considered as incidental in nature.

The viability index (no. of live offspring at day 4 / no. of live offspring at birth x 100) was slightly lower in the HD group (92.15 %) when compared to 100 % in the control group and the LD group. This clearly reduced survivability due to interim death of several pups was considered as an effect of the treatment with the test item. The marginally lower viability index of 98.98 % in the MD group was related to death of one pup of one single dam and as such considered as incidental and not toxicologically relevant.

Conclusions:
On the basis of this reproduction/ developmental toxicity screening test with 1,1-Dimethylurea in male and female Wistar rats with dose levels of 100, 300, and 1000 mg/kg body weight/day the following conclusions can be made:
There were no toxicologically relevant clinical signs at any dose level tested.
At a dose level of 1000 mg/kg body weight/day toxicologically relevant, adverse effects on body weight and/or body weight gain were noted in males and females. Food consumption was also adversely effected in females at the same dose level.
Test item related, adverse effects were observed for litter data. A lower number of male pups born was evident at 1000 mg/kg body weight/day as well as a tendency towards lower mean number of total pups delivered. The mean number of live pups on post-natal day 4 was also moderately reduced at 1000 mg/kg body weight/day due to reduced survivability of pups of both genders. Increased mortality of 7.85 % was noted at 1000 mg/kg body weight/day based on death of pups on post-natal day 1 and 2. Mean pup weight on post-natal day 0 as well as total litter weight on post-natal day 0 and day 4 was adversely reduced at 1000 mg/kg body weight/day. Furthermore, there was a slight tendency towards lower mean number of corpora lutea and implantation sites and slightly higher post-implantation loss at 1000 mg/kg body weight/day for which a relation to the treatment with the test item cannot be excluded.
1,1-Dimethylurea produced no morphological evidence of toxicological properties in the reproductive organs and tissues examined histopathologically.
The NOAEL for systemic, reproductive and developmental toxicity in this study was considered to be 300 mg/kg body weight/day.
Executive summary:

A study according to OECD 421 ("Reproduction/Developmental Toxicity Screening Test") was conducted to assess the possible effects of 1,1 -Dimethylurea on male and female fertility and embryofetal development after repeated dose administration in Wistar rats.

The test item was administered daily in graduated doses to 3 groups of test animals, 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 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. Animals of an additional control group were handled identically as the dose groups but received aqua ad injectionem, the vehicle used in this study. The 4 groups comprised 10 male and 10 femaleWistarrats.

The following doses were evaluated:

Control:                        0         mg/kg body weight/day

Low Dose:                    100     mg/kg body weight/day

Medium Dose:              300     mg/kg body weight/day

High Dose:                   1000   mg/kg body weight/day

On the basis of this reproduction/ developmental toxicity screening test with1,1-Dimethylureain male and femaleWistarrats with dose levels of 100, 300, and 1000 mg/kg body weight/day the following conclusions can be made:

There were no toxicologically relevant clinical signs at any dose level tested.

At a dose level of 1000 mg/kg body weight/day toxicologically relevant, adverse effects on body weight and/or body weight gain were noted in males and females. Food consumption was also adversely effected in females at the same dose level.

Test item related, adverse effects were observed for litter data. A lower number of male pups born was evident at 1000 mg/kg body weight/day as well as a tendency towards lower mean number of total pups delivered. The mean number of live pups on post-natal day 4 was also moderately reduced at 1000 mg/kg body weight/day due to reduced survivability of pups of both genders. Increased mortality of 7.85 % was noted at 1000 mg/kg body weight/day based on death of pups on post-natal day 1 and 2. Mean pup weight on post-natal day 0 as well as total litter weight on post-natal day 0 and day 4 was adversely reduced at 1000 mg/kg body weight/day. Furthermore, there was a slight tendency towards lower mean number of corpora lutea and implantation sites and slightly higher post-implantation loss at 1000 mg/kg body weight/day for which a relation to the treatment with the test item cannot be excluded.

1,1-Dimethylurea produced no morphological evidence of toxicological properties in the reproductive organs and tissues examined histopathologically.

The NOAEL for systemic, reproductive and developmental toxicity in this study was considered to be 300 mg/kg body weight/day.

Effect on fertility: via oral route
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
300 mg/kg bw/day
Species:
rat
Effect on fertility: via dermal route
Endpoint conclusion:
no study available

Justification for classification or non-classification

According to the above named results of a screening test on reproduction and developmental toxicity (OECD 421) with a NOAEL of 300 mg/kg bw/d 1,1 -Dimethylurea does not have to be classified.

Additional information