Methylurea

Endpoint summary

Description of key information

Oral: 
LD50: > 5000 mg/kg bw , (rat, male/female, similar to OECD Guideline 401, BASF AG 1986)
LD50: > 16000 mg/kg bw, (rat, male/female, BASF Test, BASF AG 1959)
Inhalation 
LC50 > 5.7 mg /L air / 4 hrs (rat, male/female, according to OECD guideline 403, BASF AG 1990)
Dermal: 
LD50 > 2000 mg/kg bw (rat, male/female, similar to OECD Guideline 402, BASF AG 1989)

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

5 000 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating conc.

Value:

5.7 µg/m³ air

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

2 000 mg/kg bw

Additional information

There are valid in vivo data available for the assessment of the acute oral toxicity of 1 -methylurea.

Oral

In an acute toxicity study conducted by BASF AG (1986) similar to OECD Guideline 401 as a limit test, the dose of 5000 mg/kg body weight of the test substance 1-methylurea was administered by gavage to 5 rats per sex and dose. The animals were observed for a post-dosing period of 14 days for lethality and clinical signs of intoxication. No mortality and no abnormalities were observed in males and females. Body weight gain was in the expected range for males and females.

The acute oral LD50 of 1-methylurea for male and female rats was determined to be > 5000 mg/kg body weight.

 

In a second acute toxicity study conducted by BASF AG (1959) following an internal study protocol “BASF Test”, the doses of 20, 79, 316, 1260, 5010, 10000, 12600, 15850, 20420 mg/kg body weight of the test substance 1-methylurea was administered by gavage to 1 - 5 rats per dose. The animals were observed for a post-dosing period of 7 days for lethality and clinical signs of intoxication. 1/5 rats given 15850 mg/kg bw died within the first 24 hours after dosing. No other deaths were observed. The dead rat given 15850 mg/kg bw showed clinical signs as convulsions of the hind legs and stiffness of the leg muscles which was reminiscent of rigor mortis. No pathological finding with exception of slight putrefaction was found in the decedent. The survivors were not examined pathologically. No data about body weight gain were given.

The acute oral LD50 of 1-methylurea was reported as > 16000 mg/kg body weight for rats.

 

Inhalation

In a study on the acute inhalation toxicity of 1-methylurea conducted as a limit test according to OECD 403, 5 rats per sex were exposed to a liquid aerosol of the substance 1-methylurea at a concentration of 5.73 ± 0.43 mg/l (mean ± SD) for 4 hours, respectively (BASF AG 1990). The animals were observed for a post-dosing period of 14 days for lethality and clinical signs of intoxication. No deaths occurred throughout the study.

During exposure, accelerated respiration was observed in 4/10, 4/10, 3/10, and 5/10 animals (after 1, 2, 3, and 4 hours of exposure, respectively). No clinical signs were observed during the first 30 minutes of exposure. Accelerated respiration persisted in 2/10 rats after termination of exposure. From day 1 of the observation period onward, no abnormalities were observed in the animals. Body weight gain of males and females was slightly retarded during the second week of observation when compared with historical control data. No pathological findings were noted at necropsy.

 

The acute inhalative LC50 of 1-methylurea was reported as > 5.7 mg/L air per 4 hrs for female and male rats.

 

Dermal

In an acute dermal toxicity study conducted (BASF AG 1989) similar to OECD Guideline 402, a single dermal administration of the test substance 1-methylurea was performed by applying the dose of 2000 mg/kg body weight of 50 w/v solution of the test substance on an area of almost 10 % of the estimated body surface of 5 Wistar rats per sex. The duration of the semiocclusive exposure was 24 hours. At the end of the exposure period the residual test substance was rinsed with warm water. The observation period following administration was 14 days. No mortality and no abnormalities were observed in males and females. Body weight gain was in the expected range for males and females.No local abnormalities were observed in males and females.

 

The LD50 for dermal exposure of 1-methylurea was reported to be > 2000 mg/kg body weight for male and female rats.

 

Justification for classification or non-classification

Based on the oral LD50 of > 5000 mg/kg body weight for rats, 1-methylurea has not to be classified for acute oral toxicity according to directive 67/548/EEC and according to Regulation (EC) No. 1272/2008.

Based on the inhalative LC50 > 5.7 mg/L air for rats, 1-methylurea has not to be classified for acute inhalation toxicity according to directive 67/548/EEC and according to Regulation (EC) No. 1272/2008.

Based on the dermal LD50 of > 2000 mg/kg body weight for rats, 1-methylurea has not to be classified for acute dermal toxicity according to directive 67/548/EEC and according to Regulation (EC) No. 1272/2008.