title: Carcinogenesis Bioassay of Stannous Chloride (CAS No. 7772-99-8) in F344/N Rats and B6C3F1/N Mice (Feed Study).
abstract: Stannous chloride is an inorganic tin compound used as a food preservative, a stabilizer for colors, perfumes, and soaps, and as a reducing agent in tin plating. It is also used as a mordant in printing, a silvering agent for glass and plastics, a catalyst for curing phenolic resins, an additive to drilling muds, and an antisludge agent for oils. The chronic phase of a carcinogenesis bioassay for stannous chloride was conducted by feeding diets containing 1,000 or 2,000 ppm stannous chloride to groups of 50 F344/N rats and 50 B6C3F1/N mice of each sex for 105 weeks. Similar groups of untreated rats and mice served as controls. In this study, the concentrations of tin in bone, kidney, and liver were no higher than those attained in other lifetime studies utilizing 1/100 of the dose, suggesting that organ accumulation of tin was not dose dependent, but probably limited by absorption. Mean body weight gain and feed consumption of dosed and control rats and mice were comparable. Survival of high-dose male rats was somewhat lower than that of the control and low-dose groups (37/50, control; 39/50, low-dose; 30/50, high-dose). Survival of control male mice was less (P<0.05) than that of either dosed group (32/50, 42/50, 45/50); survival of the female mice appeared to be dose related (38/50, 33/50, 28/50). C-cell adenomas of the thyroid (2/50, 9/49, 5/50), C-cell adenomas or carcinomas combined (2/50, 13/49, 8/50), and adenomas of the lung (0/50, 0/50, 3/50) in male rats; and hepatocellular carcinomas or adenomas combined (3/49, 4/49, 8/49) and histiocytic malignant lymphomas (0/50, 0/49, 4/49) in female mice occurred with significant (P<0.05) positive trends and/or with significantly (P<0.05) increased incidences in the dosed groups when compared with the paired controls. However, when the lung adenomas in male rats are combined with lung carcinomas and when all lymphomas in female mice are considered, no statistical significance remains. For the thyroid C-cell tumors in male rats and for the liver tumors in female mice, the incidences in the high-dose groups were not significantly different from the historical control rates at that laboratory (C-cell tumors: 32/288, 11.1%; liver tumors: 24/297, 8%). When the historical control rate is used as a basis for comparison, the low-dose incidence of thyroid C-cell tumors remains significant (P<0.01). Under the conditions of this bioassay, stannous chloride was judged not to be carcinogenic for male or female F344/N rats or B6C3F1/N mice, although C-cell tumors of the thyroid gland in male rats may have been associated with the administration of the test chemical. Levels of Evidence of Carcinogenicity: Male Rats: Equivocal Female Rats: Negative Male Mice: Negative Female Mice: Negative