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Diss Factsheets

Toxicological information

Carcinogenicity

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Administrative data

Description of key information

In long term chronic oral toxicity/oncogenicity studies in which methylisothiocyanate was administered to rats or mice in the drinking water, the only significant changes were a decreased body weight gain and water consumption in the high dose groups. NOEL’s were 20 and 10 ppm for mice and rats, respectively. Methylisothiocyanate showed no oncogenic activity.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion
Endpoint conclusion:
no study available

Carcinogenicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no study available

Carcinogenicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Mandatory classification and self classification:

- Regulation (EC) No 1272/2008 andDirective 67/548/EEC: not classified

Additional information

No chronic toxicity/carcinogenicity studies utilizing the inhalation route were located. Two-year bioassays with the rat and mouse in which methylisothiocyanate was administered via the drinking water were reported in the draft assessment report of metham sodium (Anonymous, 2007).

Methylisothiocyanate was administered to 60 Sprague-Dawley rats/sex/group in the drinking water at concentrations of 2, 10, or 50 ppm for 104 weeks (Anonymous, 2007). Vapor loss from the water bottles was minimized with a redesign of the water bottles. Average doses over the two years were males: 0, 0.08, 0.37, or 1.60 mg/kg/day; females: 0, 0.12, 0.56 or 2.65 mg/kg/day. An additional 10 rats/sex/group were similarly treated for an interim (52 week) sacrifice. No histopathologic lesions were present in any organ at 52 weeks. Survival was similar among the groups. Water intake and body weight were decreased in males in the 50 ppm group, an effect the authors attributed to loss of palatability with the addition of methylisothiocyanate to the water. Food intake was comparable to controls. No oncogenic response was seen at any dose level.

In a 106-week study, methylisothiocyanate was given in drinking water at concentrations of 0, 5, 20, 80, 23 or 200 ppm to 70 ICR-JCR mice/sex/group (Anonymous, 2007). Calculated doses, based on drinking water analysis and water consumption were males: 0, 0.68, 2.74, 9.82, or 21.34 mg/kg/day; females: 0, 0.76, 3.04, 10.81, or 24.06 mg/kg/day. Mortality was comparable for all groups (35-56%). No specific clinical signs were observed, but ruffled hair and dull coat were noted at 80 and 100 ppm. There was decreased body weight gain in males and females at 200 ppm and in males at 80 ppm. There were no differences in food consumption. Observed changes in hematology and clinical chemistry parameters were either transient or non-dose related. There was no abnormal tissue histopathology. There were no differences in tumor types or time to appearance of tumors between the treatment groups.


Justification for selection of carcinogenicity via oral route endpoint:
No reliable study was available.

Justification for selection of carcinogenicity via inhalation route endpoint:
No reliable study was available.

Justification for selection of carcinogenicity via dermal route endpoint:
No reliable study was available.