N-nitrosamines in laboratory animal feed and bedding

Volatile nitrosamine concentrations in laboratory animal feeds and bedding were determined by gas chromatography with a thermal energy analyzer. N-nitrosodimethylamine was detected in all samples of NIH-07 meal (range of 1.2 to 65.9 parts per billion) and 62% of NIH-07 pellet samples (0.6 to 35.2 parts per billion). It was also detected in 66% of closed formula meal (1.9 to 45.1 parts per billion) and 83% of closed formula pellets (0.2 to 21.3 parts per billion). Low concentrations were found in samples of hardwood chip and corncob bedding. Less frequently found in feed samples were N-nitrosodipropylamine, N-nitrosoethylmethylamine, and N-nitrosopyrrolidine. The latter was not detected in the closed formula diets. Traces of three nitrosamines (N-nitrosodimethylamine, N-nitrosodipropylamine, and N-nitrosomorpholine) were found in a single sample of AIN-76 mineral mix. These latter two nitrosamines and N-nitrosoethylmethylamine have not been reported previously in laboratory animal feeds.