(hydroxyethyl)urea

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route

Endpoint conclusion:

no study available

Quality of whole database:

The only study on reproductive toxicity available for hydroxyethyl urea is an OECD414 pre-natal development study which does not show any adverse effects on the parental females at the 1000mg/kg bodyweight limit dose. Histopathology and organ weight in the 90 day dermal study did not indicate any adverse effects on the reproductive organs of the males and females. Therefore there is sufficient information available concerning possible effects on fertility.

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Quality of whole database:

We do not have an inhalation test for reproduction toxicity, but there is a high quality 90 study via the dermal application route. ECHA guidance allows the NOAEL from this study to be used to calculate the systemic inhalation DNEL as high dermal absorption is predicted, with an appropriate addition assessment factor of 2. The database is therefore considered to be adequate.

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Quality of whole database:

We have a dermal OECD414 pre-natal development study showing no adverse effects on the parental females and information from a 90 day dermal study on hydroxyethyl urea , on the weights of the reproductive organs and their lack of any histopathological damage for both males and females. There is sufficient information to indicate no specific concerns for possible effects on fertility of hydroxyethyl urea.

Additional information

The only information we have that is relevant to assessing the potential for hydroxyethyl urea to cause adverse effects on fertility comes from the OECD414 pre-natal development study where only the females are dosed and from the 90 day dermal study. In the OECD414 no adverse effects were seen in the parental females and in the 90 day dermal study no adverse effects were seen on the weights of the male and female reproductive organs or indication of any histopathological damage to them. When this is taken together with the general pattern of extremely low toxicity for hydroxyethyl urea, there is no scientific justification to carry out any further reproduction testing.

Short description of key information:

We have an OECD414 pre-natal development study showing no adverse effects on the parental females and information from a 90 day dermal study on hydroxyethyl urea , on the weights of the reproductive organs and their lack of any histopathological damage for both males and females.

Justification for selection of Effect on fertility via oral route:

There is no specific study available to assess possible effects on fertility and related reproductive parameters however there is data from the 90 day dermal study including histopathological examination of the reproductive organs.  OECD Guidance document 43 on reproductive toxicity testing states that Histopathological evaluations of the reproductive tissues are relatively sensitive indicators of damage and are valuable for the assessment of male reproductive toxicity.  Due to the large reserve of sperm in rats histopathology can be a more sensitive indicator of potential effects on fertility that would be seen in a reproduction study.  For females histopathology and the weights of the reproductive organs are also useful in identifying potential for effects on fertility but less so than for males. While a lack of any effect on organ weights or histopathological changes in the reproductive organs do not preclude the possibility of adverse effect on fertility and related parental reproductive parameters, where as is that case with hydroxyethyl urea such effects are not seen at the 1000mg/kg bodyweight limit dose it does not indicate the need for specific reproductive toxicity testing at this tonnage level.  The model data indicates a high level of both oral and dermal absorption both in the region of over 70% which justifies the use of the dermal NOAEL to calculate ORAL and inhalation long term DNELs.

Also the lack of any effect in the OECD414 pre-natal development study does not indicate any concern for adverse reproductive effect in the parental females.  Therefore it is not scientifically justified at this time to carry out any reproduction studies.

Justification for selection of Effect on fertility via inhalation route:

We do not have an inhalation study investigating possible reproductive effects of hydroxyethyl urea.  The low vapour pressure and the fact that it is manufactured and handled as a solution in water, means that inhalation exposure is not expected.   ECHA guidance allows for the calculation of a systemic inhalation DNEL based on the dermal NOAEL (a NOEL at a limit dose), with appropriate assessment factors.  This is supported by the Epiwin predication of the same high absorption percentage (77-78%) for both the oral and dermal routes of exposure.  There is an adjustment by a factor of 2 to allow for expected higher absorption via inhalation compared to ingestion, this assumes 50% absorption via the dermal (or oral) route which is probably conservative in this case.  Therefore it is not considered scientifically justified to perform an animal study by the inhalation route.

Justification for selection of Effect on fertility via dermal route:

The only study we have investigating possible reproductive effects of hydroxyethyl urea is a dermal OECD414 pre-natal development study.  This study showed no adverse reproductive effects in the parental females at the 1000mg/kg bodyweight limit dose.  There is also data from the 90 day dermal study in particular from the weights and histopathological examination of the reproductive organs.  OECD Guidance document 43 on reproductive toxicity testing states that,” Histopathological evaluations of the reproductive tissues are relatively sensitive indicators of damage and are valuable for the assessment of male reproductive toxicity”.  Due to the large reserve of sperm in rats histopathology can be a more sensitive indicator of potential effects on fertility that would be seen in a reproduction study.  For females histopathology and the weights of the reproductive organs are also useful in identifying potential for effects on fertility but less so than for males. While a lack of any effect on organ weights or histopathological changes in the reproductive organs do not preclude the possibility of adverse effect on fertility and related parental reproductive parameters, where as is that case with hydroxyethyl urea such effects are not seen at the 1000mg/kg bodyweight limit dose it does not indicate any need for specific reproductive toxicity testing at this tonnage level.

Effects on developmental toxicity

Description of key information

We have Klimisch I validity OECD414 pre-natal development study in rats by the dermal route.  This study showed no adverse effect on the development of the foetuses even with parental females dosed at the 1000mg/kg bodyweight limit dose.  

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 2001-08-14 to 2002-03-07

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP and guideline conform study

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

: two listed deviations which according to the author had not an impact on the validity or integrity of the study from a scientific or GLP perspective.

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc, Portage, Michigan
- Age at study initiation: approximately 84 to 90 days of age
- Weight at study initiation: from 200 to 225 g
- Fasting period before study: no
- Housing: individually in suspended stainless steel cages
- Diet (e.g. ad libitum): PMI Certified Rodent Chow® #5002 (Purina Mills, Inc) ad libitum
- Water (e.g. ad libitum): municipal tap water ad libitum
- Acclimation period: three hours on one day to Elizabethan collars

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 to 26
- Humidity (%): 30 to 70
- Air changes (per hr): 10 to 15
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

dermal

Vehicle:

unchanged (no vehicle)

Details on exposure:

TEST SITE
- Area of exposure: no data
- % coverage: approximately 10%
- Time intervals for shavings or clipplings: for shavings - 18 hours, for clipplings - prior to the first application (gestation day 5) and when necessary thereafter

REMOVAL OF TEST SUBSTANCE
- Washing (if done): with gauze moistened with tap water
- Time after start of exposure: 6 hours

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.15 mL/animal (100 mg/kg/day group), 0.49 mL/animal (330 mg/kg/day group), 1.49 mL/ animal (control and 1000 mg/kg/day groups)
- Constant volume or concentration used: no

USE OF RESTRAINERS FOR PREVENTING INGESTION: yes

Analytical verification of doses or concentrations:

no

Details on mating procedure:

- Impregnation procedure: purchased timed pregnant
- Length of cohabitation: three days

Duration of treatment / exposure:

6 h/day

Frequency of treatment:

daily

Duration of test:

from gestation day 6 through gestation day 19

Remarks:

Doses / Concentrations:
0, 100, 330, 1000 mg/kg/day
Basis:
nominal conc.
based on hydroxyethyl urea contained in test substance at a level of 57.58%

No. of animals per sex per dose:

25

Control animals:

other: yes: reverse osmosis deionized (RODI) tap water

Details on study design:

- Dose selection rationale: dosage levels for the study were selected in an attempt to produce graded responses to the test article. The high-dose level was expected to produce toxic effects, but not excessive lethality. The mid-dose level was expected to produce no or minimal observable effects. The low-dose level was expected to produce no observable effects. Dosage levels were selected on the basis of available data from previous studies, including the dose range-finding leratology study in rats.

Maternal examinations:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: on gestation day 0 (from animal supplier) and a minimum of once daily

BODY WEIGHT: Yes
- Time schedule for examinations: on gestation days 0 (from animal supplier), 5, 6, 9, 12, 15, 19 and 20. Body weight changes were reported for the following gestation intervals: 0-5, 5-6, 6-9, 9-12, 12-15, 15-19, 19-20 and 6-19 (summary only).

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: viscera of thoracic, abdominal and pelvic cavities

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: viable fetuses, fetal sex ratios and mean fetal body weights

Fetal examinations:

- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [half per litter]
- Skeletal examinations: Yes: [half per litter]
- Head examinations: Yes

Statistics:

Inferential statistical analyses were performed by the SLI Alpha DS-10 computer system. Maternal survival, the incidence of females with total implant loss, the incidence of females with viable fetuses, and fetal malformation and variation data were compared among the groups by R x C Chi-square test, followed by Fisher's Exact Test for group-wise comparisons to the control group, when appropriate. Maternal body weights, body weight gain, food consumption, gravid uterine weights, corpora lutea counts, number of implantation sites, number of live fetuses, and fetal body weights were analyzed by one-way analysis of variance (ANOVA) followed by Dunnett's test for group-wise comparisons to the control group, when appropriate. In addition to mean and standard deviation (SD) calculations, group mean percentages were calculated for the following cesarean section parameters: pre-implantation loss, fetal sex distributions, post-implantation loss, dead fetuses, and early and late resorptions. The percentage data, the number of dead pups, and the number of early and late resorptions were analyzed by Kruskal-Wallis non-parametric ANOVA. When employed, Kruskal-Wallis was used for both the multiple group comparisons and group-wise comparisons to the control group, as appropriate. All calculations and statistical analyses were based on the dam or litter as the experimental unit. All statistical comparisons were two-tailed and utilized a minimum level of alpha at p < 0.05.

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
No mortality or clinical signs of toxicity were noted during the study. Mean food consumption of females in the 1000 mg/kg/day group was statistically lower than in controls during gestation days 12-15 and 15-19 and throughout the overall treatment period (gestation days 6-19). However, there were no statistically significant differences in mean body weights or body weight gain between the control and test article-treated groups. Similarly, there were no statistically significant differences in gravid uterine weights, maternal body weight changes or corrected maternal body weight change between the control and test article-treated groups on gestation day 20. Maternal gross necropsy findings were generally unremarkable. There were no statistically significant differences between the control and test article-treated groups in the cesarean section parameters, including the mean number of corpora lutea, implantation sites, viable foetuses, early and late resorptions, pre- and post-implantation loss, foetal sex ratios and mean foetal body weights.

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

act. ingr.

Basis for effect level:

other: maternal toxicity

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

act. ingr.

Basis for effect level:

other: developmental toxicity

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
There were no statistically significant or toxicologically meaningful differences in the incidence of foetal malformations or developmental variations between the control and test article-treated groups.

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

act. ingr.

Sex:

not specified

Basis for effect level:

other: foetal malformations or developmental variations

Abnormalities:

not specified

Developmental effects observed:

not specified

Conclusions:

Based on the results, a dosage level of 1000 mg/kg/day (active ingredient) was considered to be the no-observed-adverse-effect level (NOAEL) for maternal toxicity and a dosage level of 1000 mg/kg/day (active ingredient) was considered to be the no-observed-effect level (NOEL) for developmental toxicity in this study following dermal administration of EXP3982 (N-2-hydroxyethylurea) to pregnant rats during the period of major organogenesis.

Executive summary:

In the GLP and OECD guideline conform study, 25 female Sprague-Dawley rats per group were exposed dermally to 0 (RODI water), 100, 330 and 1000 mg/kg bw/day of hydroxyethyl urea (based on test material EXP 3982 (N-2 -hydroxyethylurea)) for approximately six hours daily from gestation day 6 through gestation day 19. Elizabethan collars were placed around the neck of each animal during the six-hour exposure period, the collars were then removed and the test site was wiped clean with gauze moistened with tap water. The dosing sites were clipped free of hair prior to the first application and when necessary thereafter. A collar check was performed a minimum of once daily during the six-hour exposure period. The animals were observed daily for clinical signs of toxicity. The test site was examined for erythema and oedema prior to dosing on gestation days 6, 9, 12, 15 and 19 and prior to scheduled euthanasia on gestation day 20. Individual body weights were recorded on gestation days 0 (from the supplier), 5, 6, 9, 12, 15, 19 and 20. Individual food consumption was recorded on gestation days 6, 9, 12, 15, 19 and 20. All females were euthanised by carbon dioxide inhalation on gestation day 20 and subjected to cesarean section. Foetuses were individually weighed, sexed and examined for external and visceral or skeletal abnormalities.

No mortality or clinical signs of toxicity were noted during the study. Mean food consumption of females in the 1000 mg/kg/day group was statistically lower than controls during gestation days 12-15 and 15-19 and throughout the overall treatment period (gestation days 6-19). However, there were no statistically significant differences in mean body weights or body weight gain between the control and test article-treated groups. Similarly, there were no statistically significant differences in gravid uterine weights, maternal body weight changes or corrected maternal body weight change between the control and test article-treated groups on gestation day 20. Maternal gross necropsy findings were generally unremarkable. There were no statistically significant differences between the control and test article-treated groups in the cesarean section parameters, including the mean number of corpora lutea, implantation sites, viable foetuses, early and late resorptions, pre- and post-implantation loss, foetal sex ratios and mean foetal body

weights. There were no statistically significant or toxicologically meaningful differences in the incidence of foetal malformations or developmental variations between the control and test article-treated groups.

Based on the results of this study, a dosage level of 1000 mg/kg/day (based on hydroxyethyl urea) was considered to be the no-observed-adverse-effect level (NOAEL) for maternal toxicity and developmental toxicity in this study following dermal administration of EXP3982 (N-2-hydroxyethylurea) to pregnant rats during the period of major organogenesis. Bsed on these results hydroxyethyl urea is not classified for developmental toxicity by CLP/GHS criteria as no effects were seen.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no study available

Quality of whole database:

There is a Klimisch 1 validity OECD414 pre-natal development study on hydroxyethyl urea via the dermal route of exposure. The lack of any adverse structural or development effect in the foetuses in this study at the 1000mg/kg bodyweight limit dose indicates no concern for developmental toxicity. The database is therefore considered to be adequate.

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Quality of whole database:

There is no inhalation study available for hydroxyethyl urea that provides information on possible developmental toxicity. There is however a Klimisch 1 validity OECD414 pre-natal development study on hydroxyethyl urea via the dermal route of exposure. Inhalation is not an expected route of exposure for hydroxyethyl urea as it has a low vapour pressure and is manufactured and handled as a solution in water. ECHA guidance allows with justification the NOAEL from this study to be used to calculate the systemic inhalation DNEL, as the Epiwin model predicts the same high absorption of 77-78% by the dermal route as for the oral route. ECHA guidance assumes 50 % absorption by the oral route and 100% by inhalation by the use of an appropriate addition assessment factor of 2. This can be seen to be a conservative approach. As the dermal NOAEL is in fact a NOEL at a limit dose, this is a conservative assessment. The database is therefore considered to be adequate.

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

We have Klimisch I validity OECD414 pre-natal development study in rats by the dermal route. This study showed no adverse effect on the development of the foetuses even with parental females dosed at the 1000mg/kg bodyweight limit dose. The database is therefore considered to be adequate

Additional information

The available information concerning the potential for hydroxyethyl urea to cause adverse effects on fertility, other reproductive parameters and the survival and development of the foetus are from a dermal OECD414 pre-natal development study in rats and from the weights of the reproductive organs and their histopathological examination. These studies showed no adverse effects on any of the parameters even at the 1000mg/kg bodyweight limit dose. The lack of any adverse effects in the 90 day dermal study and the general lack of any toxic effect from hydroxyethyl urea taken with these results do not indicate any potential for adverse effect on reproduction or development of the foetus. While we have no data by the oral and dermal routes of exposure, neither of these are exposure routes of exposure for hydroxyethyl urea. The Epiwin model data predicts a high level of both oral and dermal absorption both in the region of 77-78% which justifies the use of the dermal NOAEL to calculate ORAL and inhalation long term DNELs.The fact than the DNELs will be based on a NOEL i.e. the lack of any effects at 1000mg/kg bodyweight which will be used as the NOAEL for the calculation will result in conservative DNELs. The use of DNELs based on the 90 day study will provide addition assessment factors than the use of DNELS based on the OECD414 NOAEL also of 1000mg/kg bodyweight resulting in the lower DNELs.

Justification for selection of Effect on developmental toxicity: via oral route:

There is a Klimisch 1 validity OECD414 pre-natal development study on hydroxyethyl urea via the dermal route of exposure.  Absorption through the skin is expected and this is most likely route of exposure to this substance.  The Epiwin model predicts similar high (77-78%) absorption by both the oral and dermal routes of exposure, this support extrapolation form the dermal to oral routes of exposure. The lack of any adverse structural or development effect in the foetuses in this study at the 1000mg/kg bodyweight limit dose indicates no concern for developmental toxicity.  Therefore it is not scientifically justified to repeat the study by the oral route.

Justification for selection of Effect on developmental toxicity: via inhalation route:

We do not have an inhalation study investigating possible developmental toxicity. There is however a Klimisch 1 validity OECD414 pre-natal development study on hydroxyethyl urea via the dermal route of exposure.  ECHA guidance allows with justification the NOAEL from this study to be used to calculate the systemic inhalation DNEL, as the Epiwin model predicts the same high absorption of 77-78% by the dermal route as for the oral route.  ECHA guidance assumes 50 % absorption by the oral route and 100% by inhalation by the use of an appropriate addition assessment factor of 2.  Inhalation is not an expected route of exposure for hydroxyethyl urea as it has a low vapour pressure and is manufactured and handled as a solution in water.  The lack of any adverse structural or development effect in the foetuses in this study at the 1000mg/kg bodyweight limit dose indicates no concern for developmental toxicity.  Therefore it is not scientifically justified to repeat the study by the inhalation route.

Justification for selection of Effect on developmental toxicity: via dermal route:

We have Klimisch I validity OECD414 pre-natal development study in rats by the dermal route.  This study showed no adverse effect on the development of the foetuses even with parental females dosed at the 1000mg/kg bodyweight limit dose.  The Epiwin model predicts the same high absorption of 77-78% for the dermal as the oral route. This study is therefore adequate for assessing the possible potential for developmental toxicity from exposure to hydroxyethyl urea.

Justification for classification or non-classification

The available information concerning the potential for hydroxyethyl urea to cause adverse effects on fertility, other reproductive parameters and the survival and development of the foetus are from a dermal OECD414 pre-natal development study in rats and from the weights of the reproductive organs and their histopathological examination. These studies showed no adverse effects on any of the parameters even at the 1000mg/kg bodyweight limit dose. The Epiwin model data predicts a high level of dermal absorption in the region of 77-78% which justifies the use of the dermal route for these studies and their subsequent use for a classification decision.There were no adverse effects on reproductive parameters or development of the foetus; therefore there is no requirement to classify hydroxyethyl urea toxicity as toxic to reproduction according to the EU CLP (GHS) criteria.