TSNA levels in machine-generated mainstream cigarette smoke: 35years of data.

Highlights: [•] We gathered 35years of published data of NNK and NNN levels in cigarette smoke. [•] We augmented these data with internal, unpublished data from Philip Morris USA Inc. [•] The data suggest TSNA levels have not increased in cigarette smoke over time. [•] The data suggest TSNA levels have declined in cigarette smoke over the past 10years. [ABSTRACT FROM AUTHOR]