Melamine

Acute Toxicity: oral

Administrative data

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: NTP studies are considered as high quality studies, even if GLP was formally not stated and some standard methods were not applied. The studies are peer reviewed.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1983

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

1984

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: NTP standards

Principles of method if other than guideline:

Groups of five male and five female rats were administered single doses of melamine (2150 to 10000 mg/kg body weight) in corn oil by gavage.

GLP compliance:

not specified

Test type:

standard acute method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Melamine

EC Number:

203-615-4

EC Name:

Melamine

Cas Number:

108-78-1

Molecular formula:

C3H6N6

IUPAC Name:

1,3,5-triazine-2,4,6-triamine

Details on test material:

- Name of test material (as cited in study report): melamine.
- Analytical purity: Results of purity and identity analyses conducted at Midwest Research Institute (MRI) indicated that both lots were similar in purity in all respects.
Results of elemental analyses for both lots agreed with the theoretical values. Titration of one amino group indicated that both lots were approximately 100 % ± 1 % pure. For both lots, only one spot was detected by thin-layer chromatography.
- Impurities (identity and concentrations): Several minor impurities were detected in both lots by high-performance liquid chromatography (HPLC). The impurities were not further characterized, but 6-amino-s-triazine-2,4-diol and 4,6-diamino-s-triazine- 2-ol are reported to be common impurities in melamine.
The differences in purity determined by HPLC and titration could be due to impurities with titratable amine groups, such as the impurities mentioned above, that would result in an apparently high titration value. In addition, the detector response in HPLC is highly dependent upon the absorbance of the substance at the detector wavelength used. The values reported are absolute areas expressed as percentages of the area of the major peak and do not take into account the different values of the compound and its impurities at 254 nm. Therefore, the relative areas determined by HPLC do not necessarily reflect the actual weight percentages of the impurities in the sample.
- The infrared and ultraviolet spectra of both lots were consistent with the literature spectra.
- Lot/batch No.: Technical-grade melamine was obtained in two batches from American Cyanamid Company (Bound Brook, NJ).
Lot No. A7-11-75 was used for the single-dose and prechronic studies and for the first 14 months of the chronic study.
Lot No. A13179 was used for the remainder of the chronic studies.
- Stability under test conditions: The chemical was stable at 60 °C for 2 weeks and therefore required no special storage temperature.
- Storage condition of test material: The chemical was stored at 4 °C throughout the study, and periodic analyses by thin-layer chromatography and infrared spectroscopy indicated that no significant degradation occurred over the lifetime of the study.

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Frederick Cancer Research Center, Frederick, MD
- Age at study initiation: 10 weeks.
- Housing: Rats were housed two-three per cage in polycarbonate cages covered with nonwoven polyester filter sheets. Racks and filters were changed once every 2 weeks. Cages, bedding, and glass water bottles (equipped with stainless steel sipper tubes) were replaced twice per week.
- Diet: Purina Laboratory Chow. Ralston Purina Co. Stainless steel feed containers were changed once per week.
- Water: tap water (acidified with hydrochloric acid to pH 2.5)
Test diets, control diets, and tap water were available ad libitum.
- Bedding: Absorb-Dri heat-treated hardwood chips, changed twice per week.
- Acclimation: 6 weeks
- Randomization: No.

ENVIRONMENTAL CONDITIONS
- Temperature, humidity: The temperature in the animal rooms was 22 °- 26 °C and the relative humidity was 30 %-70 %.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

VEHICLE
- corn oil.

Doses:

2150, 3160, 4640, 6810 or 10000 mg/kg body weight

No. of animals per sex per dose:

5 males/5 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Observed for mortality every 30 min. for first 8 hrs. and then daily for 14 days.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, organ weights, histopathology, other: No.

Statistics:

Probit analysis (Finney, 1964) which based on deaths occurring within 14 days of administration of melamine.

Results and discussion

Preliminary study:

No

Effect levels

Effect levels 1

Sex:

male

Dose descriptor:

LD50

Effect level:

ca. 3 161 mg/kg bw

95% CL:

ca. 1 344 - 4 722

Effect levels 2

Sex:

female

Dose descriptor:

LD50

Effect level:

ca. 3 828 mg/kg bw

95% CL:

ca. 2 787 - 5 255

Mortality:

Deaths of animals administered a single dose of melamine were dose related. All rats that received 6810 or 10000 mg/kg body weight died.

Clinical signs:

other: no data.

Gross pathology:

White crystals (not further identified) were found in the stomach of 3/5 males and 4/5 females that received 10000 mg/kg body weight, 4/5 males and 5/5 females that received 6810 mg/kg body weight, 1/5 males and 2/5 females that received 3160 mg/kg body weight, and 1/5 males that received 2150 mg/kg body weight.

Applicant's summary and conclusion

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Melamine has a low acute toxicity.

Executive summary:

Groups of five male and five female rats were administered single doses of melamine (2150 to 10000 mg/kg body weight) in corn oil by gavage. Animals were observed for 2 weeks.

Deaths of animals administered a single dose of melamine were dose related. All rats that received 6810 or 10000 mg/kg body weight died. The LD50 was calculated to 3161 mg/kg for males and 3828 mg/kg for females.