Bioavailability of tobacco-specific N-nitrosamines to the snuff dipper.

Use of supercritical carbon dioxide extraction in the analysis of smokeless tobacco for tobacco-specific N-nitrosamines revealed the presence of higher levels of 4-(methylnitros-amino)-1-(3-pyridyl)-1-butanone (NNK) than had been determined with conventional methods. Whether human saliva may be similarly capable of releasing apparently bound NNK during chewing or snuff dipping was tested by incubating smokeless tobacco with enzymatically active saliva and with heat-treated saliva respectively. Enzymatically active human saliva was found to liberate up to twice the amount of the highly carcinogenic NNK than did heat-treated saliva. This is of major consequence for the cancer risk assessment of snuff dippers and tobacco chewers.