In the United States, secondhand smoke is the third leading preventable cause of death. Flavored hookah (waterpipe) tobacco smoking, a highly social activity common in hookah bars, is a key source of SHS exposure. While smoke-free air laws have decreased exposure to secondhand smoke, the majority of laws do not include hookah smoking. Thus, as a social outlet for youth and young adults, hookah smoke exposure may harm non-smokers, including women of reproductive age or pregnant, hookah bar workers, children, and individuals with heart and lung disease. While more is known on the acute effects of active hookah smoking and the literature is emerging on active e-hookah vaping, little is known about the acute vascular effects of secondhand exposure to hookah smoke and aerosol. The study aims to examine the acute effects of secondhand exposure of hookah smoke and aerosol on endothelial and vascular function. Eligible volunteers will be invited to participate in a total of 3 study visits (2-3 hours each): e-hookah aerosol exposure, charcoal-heated hookah smoke exposure and smoke-free room air. Non-invasive blood pressure and blood flow measurements will be taken before and after the exposure sessions.

Inclusion Criteria:

• 21-49 years old
• Never a smoker: do not use any tobacco products or nicotine delivery systems, including cigarettes, cigars (traditional and filtered), cigarillos, hookah, smokeless tobacco (i.e., loose snus, moist snuff, dip, spit, or chewing tobacco), pipe tobacco, snus pouches, dissolvable tobacco or vaping.
• no evidence of cardiopulmonary disease by history/physical
• blood pressure (BP) < 140/90 mmHg
• resting heart rate (HR) < 100 bpm
• BMI >18 or < 30kg•m2
• no prescription medication
• No exposure to environmental tobacco smoke for at least one week prior to the study date.

Exclusion Criteria:

• exhaled carbon monoxide >6 ppm
• (+) pregnancy test
• other conditions deemed unsafe to participate, such as breastfeeding