Urea, reaction products with formaldehyde and glyoxal

Endpoint summary

Description of key information

The subchronic NOAEL for oral application is 3000 mg/kg in rats and 6000 mg/kg in mice (as 100% substance each). There are no data available concerning repeated dose toxicity by dermal application or inhalation. The NOAEL of 3000 mg/kg has been taken as starting point for DNEL derivation.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Peer reviewed database.

Principles of method if other than guideline:

Performed according to the NTP protocol

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

Ninety three male and 96 female Fischer 344 rats were acclimated for a period of 15 days before treatment. Based on daily observations and a pre-initiation health verification conducted one week prior to study initiation, 90 males and 92 females were selected for possible use on study. A gross necropsy was performed on five males and 5 females one day prior to test initiation. All rats examined were found to be disease and parasite-free. Animals were randomly allocated to 4 groups of 10 animals/sex. They were 44-51 days old at study initiation. Males weighed 104-161 g and females weighed 96-115 g. Food and water were available ad libitum.

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

Doses were given at a volume of 20 ml/kg.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Representative solutions were analyzed immediately after preparation at two labs. A sample taken from the 1000 mg/kg dosage level solution was analyzed to be 110% of the target concentration at one lab and 97% of the target concentration at the other lab.

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

5 days/week

Remarks:

Doses / Concentrations:
1000; 3000; 6000 mg/kg (referring to 100 % substance)
Basis:

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

Post-exposure period: no

Observations and examinations performed and frequency:

Animals were weighed prior to dosing, at weekly intervals, and at termination. Animals were observed daily for mortality and clinical signs of toxicity.

Sacrifice and pathology:

All survivors were euthanized on day 91 and received complete post-mortem examinations. The brain, lung, heart, thymus, liver, right testis and right kidney were weighed and relative weights (to brain and body) were calculated. These tissues, plus the pituitary, eyes, nasal cavity and turbinates, oral cavity, larynx and pharynx, tongue, salivary gland, Zymbal's gland, trachea, thyroid, parathyroid, mandibular lymph node, esophagus, stomach, duodenum, jejunum, ileum, colon, cecum, rectum, sternum (with marrow), aorta, costochondral junction (rib), spinal cord, mammary gland, skin, mesenteric lymph node, pancreas, spleen, adrenal, urinary bladder, testes with epididymis, tunica of the testis and scrotal sac, seminal vesicles, prostate, ovary, uterus, preputial or clitoral gland, thigh muscle, blood smear, sciatic nerve, gross lesions, tissue masses or suspect tumors and regional lymph nodes were saved in neutral 10% formalin. Stained sections of all collected organs from the high dose and control animals (except the tongue, Zymbal's gland, costochondral junction (rib), skin, seminal vesicles, thigh muscle and sciatic nerve) were examined histologically. The eyes and pharynx were only examined if grossly abnormal. Histologic sections of heart and testis were examined for the low and mid-dose males.

Other examinations:

At study termination, serum samples from 5 rats/sex from the control groups were analyzed for the presence of antibodies to murine viruses designated by the NTP. Positive titers to both Sendai (all rats) and PVM virus (all females) were detected using a hemagglutination inhibition assay.

Statistics:

Body and organ weight data of treated animals were compared to controls using a one-way analysis of variance, Bartlett's test for homogeneity of variances and the appropriate t-test (for unequal and equal variances) as described by Steel and Torrie. Dunnett's multiple comparison tables were used to assess significant differences at p < 0.05.

Details on results:

Three males of the 6000 mg/kg/day dosage level were found dead on study day three. The cause of one of the deaths was aspiration pneumonia. The cause of death of the other animals was not determined. The males in the 6000 and 3000 mg/kg/day dosage level groups exhibited a lower mean body weight gain and had lower body weights at termination (314 +/- 18.1 g and 331 +/-27.1 g, respectively) than controls (358 +/- 31.1 g). The mean body weights of the males of the 1000 mg/kg/day dosage level and of the treated female rats were comparable to controls throughout the study.
Pharmacotoxic signs noted for male and female animals in the 3000 and 6000 mg/kg/day dosage level groups included primarily yellow discoloration of fur in the anogenital region and soft stool. In addition, male animals in the 6000 mg/kg/day dosage level group exhibited yellow discoloration of fur - abdominal region and soft stool. One male animal in the 6000 mg/kg/day dosage level group was noted for hypoactivity, decreased grasping reflex, extremities hypothermic to touch, and ataxia on study day 3. Other signs noted among rats of various dosage level groups, or controls, were considered incidental and unrelated to the test article.
No toxicologically significant organ weight changes occurred in this study. Macroscopically, one male from the 6000 mg/kg/day dosage level group was found at the post-mortem examination to have multiple yellowish linear macroscopic lesions in the right testis. Microscopically, the lesions were found to be moderate bilateral mineralization of testes. Microscopically, treatment related mild mineralization in the heart was seen in this male and another male in the 6000 mg/kg/day dosage level group. Mineralization in the testes and heart were considered to be test article-related lesions. No other macroscopic or microscopic findings were considered to be related to the test article.

Dose descriptor:

NOAEL

Effect level:

3 000 mg/kg bw/day (nominal)

Sex:

male

Dose descriptor:

NOAEL

Effect level:

6 000 mg/kg bw/day (nominal)

Sex:

female

Critical effects observed:

not specified

Conclusions:

Effects on body weight of the 3000 mg/kg males were regarded as not adverse due to the relative low strength of effect (-7.5%) and the solitary appearance of this effect in this treatment.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

3 000 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Oral:

The following evaluation of the repeated dose toxicity by oral application is based on the assessment in course of the OECD SIDS program, 2002: 

“In a 14-d repeated-dose toxicity study, male and female rats and mice (F-344 rats and B6C3F1 mice) were administered the test article by oral intubation at doses from 256 to 11680 mg/kg bw/d (100% substance) (in total 12 treatments) (IRDC, 1983a,b). No intoxication or toxicological significant macroscopic lesions or organ weight variations were evident in both species. Microscopically, no significant pathological events but the occurrence of a moderately inflammatory bilateral reaction in the nasal passages of the highest-dosed rats were found.

 

In two 90-d studies which were under the direction and support of the U.S. National Toxicology Program (NTP), groups of F-344 rats (10 male, 10 female each) and of B6C3F1 mice (10 male, 10 female each) received 1000, 3000 and 6000 mg DMDHEU (100%)/kg bw/d by gavage (IRDC, 1983 a&b). Reanalysis showed that the test solution contained 41 .5 % of DMDHEU and 0.32 % of free formaldehyde (IRDC, 1983 b).

In the rats (IRDC, 1983a), mean body weight gain was retarded in the male top and median dose group, but not in females. No significant differences were seen at the 1000-mg dose level in both sexes. Yellow discoloration of the fur in the abdominal/ anogenital region and soft stool were prominent at the higher doses. One male in the high-dose group was noted for hypoactivity, decreased grasping reflex, hypothermic extremities, and ataxia. Other clinical signs at various dose levels were considered incidental and unrelated to the test article. No toxicologically significant organ weight changes occurred. At macroscopic post-mortem examination, no specific lesions were detected, but one high-dosed male having multiple yellowish linear macroscopic lesions in the right testis. Histopathological inspection revealed no specific treatment-related organ lesions, except that two males of the 6000 mg/kg dosage level group suffered from mild mineralization in the heart, and one from moderate bilateral mineralization of the testes, both phenomena considered substance-related. No such damage was seen in the 3000-mg groups.

In mice, mean body weight gain was equal or significantly higher than the control. Microscopic examination of the tissues from mice of the control and 6000 mg/kg groups gave no indication to treatment-related morphological changes . Chronic interstitial pneumonia was not influenced or induced by DMDHEU because in both the control and the high-dose group this disease was ~ correlated with serum positivity of the Sendai virus (IRDC, 1983b).

 

Conclusions:

Available experimental data are based on reliable studies conducted within the scope of the toxicological program under the auspices of U.S. NTP. The results clearly confirm the low toxicity already noted under single-dose conditions. The subchronic NOAEL for oral application was 3000 mg/kg in rat and 6000 mg/kg in mice (as 100% substance each).”

Dermal:

There are no data available concerning repeated dose toxicity by dermal application of the test substance.

Inhalation:

There are no data available concerning repeated dose toxicity by inhalation of the test substance.

Justification for classification or non-classification

GHS classification according to Annex I 1272/2008 CLP (EU GHS):

no classification warranted