Inclusion Criteria:  adults aged 21 years or above self-reported smoking at least 10 cigarette/day for the past year with no intention to quit expired carbon monoxide level of more than 8 ppm at recruitment willingness to participate in the proposed study access to a functional telephone expected presence in the study's geographical area for the next 4 months not currently enrolled in any smoking cessation programs female subjects of childbearing potential will be required to practice acceptable methods of birth control (the acceptable methods of birth control include birth control pills, Birth Control Shot, Birth Control Implant, Intrauterine Device [IUD], Diaphragm, and cervical cap)  Exclusion Criteria:  diagnosed with cancer (other than non-melanoma skin cancer) diagnosed with liver dysfunction or with previous liver diseases levels of alanine transaminase, aspartate transaminase, alkaline phosphatase, or total bilirubin over limit of normal range at prescreen inability to refrain from acetaminophen, alcohol (no more than one drink daily via self-report), or other potentially hepatotoxic substances use any other non-cigarette nicotine containing products such as smokeless tobacco, cigar or e-cigarettes are pregnant or nursing (lactating) or of childbearing age planning to become pregnant or unwilling to use adequate contraception during the study