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NNN, NNK and NAT levels on a dry weight basis in smokeless tobacco products at the end of product stability testing period from 2008 to 2017. The top panel is NNN, middle panel is NNK and bottom panel is NAT. Boxes represent the 25th and 75th percentile value and the whiskers indicate the 10th and 90th percentile. The median is the horizontal bar within the box. The number of lots measured per product per year is given in the supplemental information.
