Short-Term Cardiovascular Effects of E-Cigarettes: Influence of E-Liquid pH

Inclusion Criteria: * Heart rate \< 105 beats per minute (BPM)\* * Systolic Blood pressure \<160 and \> 90\* * Diastolic Blood Pressure \<100 and \> 50\* * Body Mass Index (BMI) \< 38.0 (at investigator's discretion for higher BMI if no other concurrent health issues) \*considered out of range if both machine and manual readings are above/below these thresholds * Use e-cigarettes on at least 15 days in the past 30 for at least 3 months * Smoke 10 or fewer cigarettes/tobacco products per day in the last 30 days * Willing to use mod e-cigarette * Willing to abstain from tobacco product use for night before study * Age: \> 21 years old and \< 70 years old * Using e-liquid \> 0mg/ml nicotine * Saliva cotinine of ≥ 30 ng/ml or NicAlert=6 (in cases where lab turn around time will delay study procedure) Exclusion Criteria: * Seizures * Cancer * Hepatitis B or C or Liver Disease * Oral Thrush * Heart disease * Glaucoma * Kidney disease or urinary retention * Diabetes * High Blood Pressure (taking sympatholytic medications such as alpha and beta blockers) * History of stroke * An ulcer in the past year * Thyroid disease (okay if controlled with medication) * Active use of an inhaler for asthma or Chronic Obstructive Pulmonary Disease (COPD) * Psychiatric conditions * Current or past schizophrenia, and/or current or past bipolar disorder * Major depression, current or within the past year * Major personality disorder * Participants with current or past minor or moderate depression and/or anxiety disorders will be reviewed by the study physician and considered for inclusion. * History of psychiatric hospitalizations are not exclusionary, but study participation will be determined as per study physician's approval * Recent onset or change in cough, fever and/or abdominal symptoms (vomiting or pain) in the past two weeks. (If yes, participant can re-screen when symptoms resolve). * Drug/Alcohol Dependence * Alcohol or illicit drug dependence within the past 12 months with the exception of those who have recently completed an alcohol/drug treatment program * Positive toxicology test at the screening visit (THC \& prescribed medications okay) * Opioid replacement therapy (including methadone, buprenorphine, or other) * Positive urine cannabis is not exclusionary but participant must report use of cannabis and agree to abstain from cannabis use for the duration of the study * Psychiatric medications * Current regular use of any psychiatric medications with the exception of Selective Serotonin Reuptake Inhibitor (SSRI) and serotonin-norepinephrine reuptake Inhibitor (SNRIs) and current evaluation by the study physician that the participant is otherwise healthy, stable, and able to participate. * Medications * Use of medications that are inducers of nicotine metabolizing enzyme CYP2A4 (Example: rifampicin, carbamazepine, phenobarbital, and other anticonvulsant drugs). * Concurrent use of nicotine-containing medications * Any stimulant medications (example: Adderall) generally given for Attention deficit hyperactivity disorder (ADHD) treatment * Use of sympatholytic medications that affect cardiovascular conditions including hypertension, (Example: beta and alpha-blockers) * Other/Misc. Chronic Health Conditions * Fainting (within the last 30 days) * Other "life threatening illnesses" as per study physician's discretion * Pregnancy * Pregnancy (self-reported and urine pregnancy test) * Breastfeeding (determined by self-report) * Concurrent participation in another clinical trial * Inability to communicate in English * Planning to quit vaping within the next 60 days * Uncomfortable with getting blood drawn