This outpatient study examines how inhaled cannabis, combustible or vaporized, alters lung health and breath biomarkers compared to a tobacco cigarette.

Inclusion Criteria:

1. English-speaking,
2. Literate adults,
3. Male or female,
4. Between the ages of 18 and 55,
5. Body Mass Index from 18.5 and 32.0 kg/m2,
6. Able to provide written informed consent and perform all study procedures,
7. Current recreational cannabis users - must report past 30-day cannabis use and at least 5 exposures in the past year (minimum use criteria); no limit on maximum use,
8. Past year history of vaporized or smoked cannabis use to intoxication,
9. Past 30-day use of combusted tobacco,
10. Not currently seeking treatment for cannabis, tobacco cigarettes, or other drug use,
11. If female, a negative pregnancy test and use of an effective form of contraception during study participation (e.g., oral contraceptive, abstinence, barrier method),
12. Negative urine drug test for drugs of abuse (other than cannabis) before every Laboratory Session, and
13. Otherwise, healthy as determined by the investigator based on medical history, physical examination, vital signs, laboratory chemistries (blood chemistry with liver function tests and hematology, urinalysis, and microscopic evaluation, 12-lead electrocardiogram).

Exclusion Criteria:

1. Physiologic drug dependence on opioids, benzodiazepines, barbiturates, and/or alcohol that would require medical management,
2. Clinically significant acute medical problem (e.g., infection) or chronic medical problem requiring daily medication or ongoing medical care (e.g., hypertension, cardiovascular disease, diabetes, respiratory disorders [e.g., asthma, COPD]),
3. Existing or significant lung health problems that could interfere with the study,
4. Current or history of major psychiatric disorder that would limit the participant's ability to participate in the study (e.g., bipolar disorder),
5. Exclusive use of tobacco or cannabis through vapes and Electronic Nicotine Delivery Systems (ENDS) products,
6. Currently using daily prescription medications to manage medical conditions or any drug that could interfere with the study (as determined by the study physician),
7. Clinically significant abnormal ECG (as determined by study physician/cardiologist),
8. Clinically significant abnormal laboratory findings (e.g., liver function tests greater than 3x the upper limits of normal range),
9. History of seizure disorder,
10. Clinically significant history of head injuries requiring medical management or long-lasting sequelae.