OBJECTIVES:~I. To characterize nicotine delivery, systemic exposure and effects from SREC in comparison with usual to usual nicotine brand use.~II. To assess aspects of harm of SREC use compared to usual nicotine brand use.~OUTLINE:~Eligible participants will be assigned to one of two treatment conditions for the initial assessment which will take place in a hospital setting. The participant will then be assigned to the second condition within 2 weeks after the initial assessment which will also take place in a hospital setting to repeat the same procedures.
This is a crossover study that will examine use behaviors, chemical exposures, and biological effects of Standardized Research Electronic Cigarette (SREC) compared to usual brand e-cigarette use in natural or synthetic nicotine users.