High Carbon Monoxide Levels From Charcoal Combustion Mask Acute Endothelial Dysfunction Induced by Hookah (Waterpipe) Smoking in Young Adults

BACKGROUND: Hookah smoking is marketed to youth as a harmless alternative to cigarettes. Although cigarette smoking acutely impairs endothelial function, the effect of smoking fruit-flavored hookah tobacco is unknown. Because charcoal traditionally is used to heat the hookah tobacco in the waterpipe, hookah smoke delivers tobacco toxicants and nicotine plus charcoal combustion products: not only carbon-rich nanoparticles, oxidants that may destroy nitric oxide and impair endothelial function, but also large amounts of carbon monoxide (CO), a putative vasodilator molecule. METHODS: To test the acute effect of hookah smoking on endothelial function, in young adult hookah smokers (n=30, age 26 +/- 1 years, mean +/- SE), we measured plasma nicotine, exhaled CO, and brachial artery flow-mediated dilation (FMD) before and after charcoal-heated hookah smoking. To remove the effect of charcoal combustion, the same measurements were performed when the same flavored hookah tobacco product was heated electrically (n=20). As a positive internal control, we studied age-matched cigarette smokers (n=15) who smoked 1 cigarette. To isolate the effect of the CO boost on FMD, hookah smokers (n=8) inhaled a 0.1% CO gas mixture to approximate their CO boost achieved with charcoal-heated hookah smoking. RESULTS: Nicotine levels increased similarly with all types of smoking, whereas exhaled CO increased 9- to 10-fold more after charcoal-heated hookah than after either electrically heated hookah or cigarette smoking. FMD did not decrease after smoking charcoal-heated hookah but instead increased by +43 +/- 7% (P<0.001). In contrast, FMD decreased by -27 +/- 4% (P<0.001) after smoking electrically heated hookah, comparable to the decrease after cigarette smoking. FMD increased markedly by 138 +/- 71% (P<0.001) after breathing CO gas, 2.8 times more than the increase induced in the same subjects after smoking charcoal-heated hookah (P<0.001), despite comparable increases in exhaled CO (24 +/- 1 versus 28 +/- 3 ppm, hookah versus CO). CONCLUSIONS: Smoking hookah tobacco, similar to cigarette tobacco, acutely impairs endothelial function. With traditional charcoal-heated hookah smoking, the acute endothelial dysfunction is masked by high levels of carbon monoxide, a potent vasodilator molecule generated by charcoal combustion. With respect to large-artery endothelial function, smoking hookah is not harmless.