2-(morpholinothio)benzothiazole

Carcinogenicity

Description of key information

The carcinogenic potential of the test substance MBS was evaluated in a chronic feeding study with Sprague-Dawley rats (Monsanto Co. 1982). The incidence of tumour-bearing animals and the pattern of tumour multiplicity did not suggest any non-specific carcinogenic effect. The incidence of common tumour types was not enhanced by treatment and there was no evidence of any site-specific carcinogenicity in treated animals. 
Based on the finding of this study a NOAEL of 400 mg/kg bw and day is suggested. 

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion

Dose descriptor:

NOAEL

400 mg/kg bw/day

Justification for classification or non-classification

No classification is required according to the classification criteria 67/548/EWG and regulation no. 1272/2008 (GHS).

Additional information

Carcinogenicity: oral

The carcinogenic potential of MBS was evaluated in a chronic feeding study with Sprague-Dawley rats (Monsanto Co. 1982). Male and female rats (main experiment 50 per dose and sex, satellite group 10 per dose and sex) were feed with the test substance MBS for 113 weeks (satellite group 54 weeks). The animals were treated with 0, 5, 50 or 400 mg/kg bw and day. Clinical changes seen in this study was generally typical of that seen in the ageing CD rat. Treatment with the test substance MBS did not appear to affect the incidence or severity of the observed changes. An increase of the mortality rate was noted in males of the mid and high dose group between week 58 and 85. Later in the study this increase declined. In treated females (mid and high dose) a lower mortality rat was seen compared to control in the latter part of the study. The body weight gain was reduced in males and females of the high dose group throughout the study. The reduced weight gain was associated with slight reductions in food consumption. In haematology no biologically relevant changes in haematological parameters were noted. In clinical biochemistry and urine analysis some changes were noted, but was considered as not biologically relevant (for more details see endpoint repeated dose toxicity).

Gross pathology examinations revealed palpable subcutaneous masses identified in a proportion of the animals in all groups in the course of the study. The masses were of the type commonly seen in the CD rat and were most frequently seen in the axillae and mammary glands. The time to first mass was not affected by treatment. Males of the mid and high dose groups showed a statistically significant increase in palpable masses, whereas the corresponding female groups showed a reduced incidence. The microscopic pathology data did not indicate this to be a carcinogenic response.

There was no apparent difference between animals of the highest dose group (400 mg/kg bw and day) and the control animals in the incidence of tumour-bearing animals or in the incidence of animals with tumours of single or multiple organ sites. The authors concluded that the incidence of common tumour types was not enhanced by treatment and there was no evidence of any site-specific carcinogenicity.

Based on the finding of this study a NOAEL of 400 mg/kg bw and day is suggested.