Registration Dossier

Administrative data

Description of key information

No carcinogenic effects observed

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Carcinogenicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no study available

Carcinogenicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Additional information

Carcinogenicity: oral

There is 2 year repeated dose feeding study in rats with Indigo (Weir RJ, 1967a; Ferber, 1987). Male and female F344/N rats (25 rats/sex/dose group) were orally fed dose levels of 0.25%, 1% or 3% indigo (100, 400, 1200 mg/kg/day) for 2 years; 80 control rats/sex received the plain diet only. No toxicologically relevant changes were observed during in-life or post-mortem observations. The study appeared to demonstrate that after a period of adjustment to the higher dosage levels, the rats were able to tolerate up to 3% of this substance in their diets without serious effects. NOEL for repeated dose toxicity is considered to be 1200 mg/kg/day no proliferative changes were observed at this dose level.

Carcinogenicity: inhalation

No data available.

Carcinogenicity: dermal

In a dermal lifetime study in mice, indigo was applied as a 1% solution (W/V) in spectro-grade benzene at a dose of 1 mg of test material (once/week) for up to 95 weeks, to 50 male and 50 female Swiss-Webster mice (Weir RJ, 1967c; Ferber KH, 1987). 100 males and 100 females were used as negative controls (no treatment). 100 males and 100 females received application of the vehicle (benzene). Microscopic examination of the skin (application site) was performed from all animals died or sacrificed in the first 9 months and of the liver from 9 to 13 mice/group. Microscopic examination of the lungs, liver and skin (application site) from 10 negative controls, 10 vehicle controls, and 10 compound-treated animals were performed at 75 weeks. At the terminal sacrifice (95 weeks), sections of lung, liver and skin from 29 negative controls, 26 vehicle controls and 13 compound-treated animals were examined microscopically. Histopathology was also performed on most tissues and on grossly abnormal organs of the animals. No evidence was found that in mice repeated dermal application of indigo at 1 mg/animal, once per week for up to 95 weeks produced any effect attributable to the test substance. Lesions and tumors seen in treated mice were comparable to those in vehicle control animals.

Justification for classification or non-classification

No evidence for carcinogenic properties