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Repeated dose toxicity: oral

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Administrative data

Endpoint:
repeated dose toxicity: oral
Remarks:
other: carcinogenicity
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Meets generally accepted scientific standards, well documented and acceptable for assessment.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1979

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
other: OECD Guideline 451 (Carcinogenicity Studies)
Deviations:
yes
Remarks:
- only 2 doses tested
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
2,4-Diaminotoluene (2,4-TDA); purity 99.9 % (gas-liquid chromatography, and with up to 6 minor
components)

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
Treatment of animals: the doses 125 and 250 ppm were given for 40 weeks; due to excessive depression in body weight gain low and high doses were then reduced to 50 and 100 ppm, respectively; administration of 50 ppm was continued for 63 weeks; surviving animals administered 100 ppm were killed at the end of 39 (males) or 44 (females) weeks due to morbidity. In another report, apparently of the same study, it was said that the 2,4-TDA doses were reduced at week 20, rather than week 40 (Cardy, 1979).

The time-weighted average dose was 79 ppm for the low-dose males and females for 103 weeks, 176 ppm for the high-dose males for 79 weeks, and 171 ppm for the high-dose females for 84 weeks. The calculated average intake of 2,4-TDA was approx. 5.9 mg/kg bw/day (low dose) and approx. 13 mg/kg bw/day (high dose).
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
up to 103 weeks
Frequency of treatment:
continuous
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 125/50 ppm (low dose), 250/100 ppm (high dose)
Basis:
nominal in diet
No. of animals per sex per dose:
50 (dose groups); 20 (control groups)
Control animals:
yes, plain diet

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related

Effect levels

open allclose all
Dose descriptor:
NOAEL
Sex:
male/female
Remarks on result:
not determinable
Remarks:
no NOAEL identified
Dose descriptor:
LOAEL
Effect level:
ca. 5.9 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
other: The time-weighted average dose over a period of 103 weeks was 79 ppm for low dose males and females; from this an average 2,4-TDA intake of approx. 5.9 mg/kg bw/day was calculated.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Mortality was dose related in male and female rats. At both dose levels, male and female rats showed a decrease in survival time compared to controls as demonstrated in table 1 after 78 treatment weeks:

Table 1: Number of rats which were still alive at week 78 on study

 Control  Low Dose  High Dose

 Males

 18/20 (90 %)  42/50 (84 %)  32/50 (64 %)

 Females

 20/20 (100 %)  46/50 (92 %)  46/50 (92 %)

All males given 250/100 ppm 2,4-TDA (high dose) were dead by 79 weeks, and females given high doses were dead or were terminated due to morbidity by 84 weeks. Mean body weights of dosed male and female rats were lower than those of the corresponding controls and were dose related. Non-neoplastic findings of this carcinogenesis bioassay in F344 rats revealed that 2,4-TDA was hepatotoxic. In the liver dosed animals exhibited various treatment induced non-neoplastic morphologic alterations which ranged from mild, scattered foci of lipidosis and focal necrosis of hepatocytes to severe, diffuse, toxic degenerative lesions. The incidence of primary hepatic lesions in rats is given in the following table 2:

Table 2: Number of rats with primary non-neoplastic lesions in the liver

 Control  Low Dose  High Dose

 Males

 2/20 (10 %)  25/49 (51 %)  36/50 (72 %)

 Females

 1/20 (5 %)  23/50 (46 %)  42/49 (86 %)

In addition, kidney lesions were seen in both sexes (most marked in males). Microscopy of the kidneys revealed non-neoplastic lesions of different severity scored in the 1-5 grading system. The average numerical values are listed by dose and sex in the following table 3:

Table 3: Scoring of chronic renal disease in rats (mean average of severity grades/number of animals tested)

 Control  Low Dose  High Dose

 Males

 2.1 / 20  3.7 / 49  3.9 / 50

 Females

 1.3 / 19  2.0 / 50  2.8 / 49

1-5 grading system mean: 1=minimal changes detectable as slight basement membrane thickening seen most in Bowman's capsule. 2=the stage of mild glomerular change and scattered, atrophic, dilated tubules with intratubular proteinaceous casts. 3 and 4=subjective divisions of degree of the above changes along with glomerular atrophy and sclerosis, lymphoid aggregates, and a variable degree of interstitial fibrosis and architectural derangement. A score of 4 indicated severe involvement. 5=reserved for end-stage kidneys.

Corresponding to the renal disease was a high incidence of associated secondary hyperparathyroidism in low- and high-dose males. The affected parathyroid glands were spherical and bulged from the surface of the cut thyroid gland. Associated lesions included metastatic calcification in numerous locations and absorption in bone with proliferation of osteoclasts and myelofibrosis.

In F344 rats an average dose of approx. 5.9 mg/kg bw/day 2,4-TDA showed hepatotoxic effects, induced the development of chronic renal disease, and an increased incidence of tumors. An overall NOAEL for rats was not demonstrated.

Applicant's summary and conclusion

Executive summary:

In a carcinogenicity study F344 rats were administered with feeding concentrations of 0, 125/50 and 250/100 ppm 2,4 -TDA over a period of up to 103 weeks. The time-weighted average dose was 79 ppm for the low-dose males and females for 103 weeks, 176 ppm for the high-dose males for 79 weeks, and 171 ppm for the high-dose females for 84 weeks. The calculated average intake of 2,4-TDA was approx. 5.9 mg/kg bw/day (low dose) and approx. 13 mg/kg bw/day (high dose). In this study survival time and mean body weights were dose related decreased in males and females. In both sexes an average dose of approx. 5.9 mg/kg bw/day 2,4-TDA showed hepatotoxic effects, induced the development of chronic renal disease, and an increased incidence of tumors. An overall NOAEL for rats was not demonstrated.