Chronic toxicity tests of sodium thiocyanate with sodium nitrite in F344 rats

Sodium thiocyanate, a common environmental chemical, was found to increase the incidence of liver tumors in a group of rats treated with 0.08% in drinking water. To test the possibility that thiocyanate was catalyzing the formation of carcinogenic nitrosamines from amines and nitrite in the food, a group of 20 male and 20 female rats was given a higher dose of sodium thiocyanate (0.32%) together with sodium nitrite (0.2%) in drinking water. Similar groups of rats were given 0.32% sodium thiocyanate or 0.2% sodium nitrite in drinking water or were untreated. All treatments lasted most of the lifetime of the rats, at least 2 years. There was no difference between the groups, treated or untreated, in survival, or in the incidence of any tumor that could be related to the treatment. The results indicate that sodium thiocyanate is without carcinogenic activity in rats, alone or combined with sodium nitrite.