Urinary levels of tNNK and tNNAL in female and male rats treated with NNK by nose-only inhalation for 14 days. Upon the cessation of the NNK exposure on days 1, 8, and 14, rats were transferred to metabolism cages for overnight urine collection for measurement of the total urinary excretion amounts of tNNK and tNNAL. The target NNK dose levels were 0 mg/kg BW (Vehicle Control), 0.8 mg/kg BW (Low), 3.2 mg/kg BW (Mid), 12.5 mg/kg BW (Mid High), and 50 mg/kg BW (High).