This study will examine the level of toxicity of e-cigarette use compared to smokers and nonsmokers including inflammation markers, toxicant and carcinogen exposure. Additionally, the study will look at the effect of varying voltage levels for e-cigarette users.

In this observational study, e-cigarette users, smokers, and non-users of e-cigarette or tobacco products (up to 134 per group) will be recruited from the Minneapolis-St. Paul area. This research will be conducted at the Tobacco Research Programs at the University of Minnesota. Subjects are screened for eligibility over the phone. If eligible after the phone screen, participants will be invited to attend orientation screening visit in the clinic where consent will be obtained and subjects will complete forms about their tobacco and e-cigarette use and medical history. Subjects who eligible will be asked to return for six visits over the course of six months.

At these appointments, subjects will provide biological specimen samples (buccal cells, urine and blood). Saliva will be collected before and after a smoking or vaping session. Non-users will only have 1 saliva collection.

Subjects will be asked for information pertaining to and e-cigarette and tobacco use and overall health.

Inclusion Criteria:

• Good physical health with no unstable medical conditions; Able to provide written informed consent; Stable and good mental health;

Meet criteria for 1 of three groups:

1. Regular smokers confirmed by CO;
2. E-cigarette users (exclusive e-cigarette use for 3 months); Non-Tobacco Users
3. Non-smokers

Exclusion Criteria:

• Unstable medical condition Not willing to attend visits

Subjects will be recruited locally within reasonable distance from the University of Minnesota.