Contributions of charcoal, tobacco, and syrup to the toxicity and particle distribution of waterpipe tobacco smoke.

The use of waterpipes in the United States is increasing in a largely unregulated market. The shisha smoked in a waterpipe is a complex matrix of tobacco, flavorings, and humectant with smoke generated by an external heat source. This study explored the relationship between shisha components and the particulate matter size distributions and toxicity of smoke generated with heating.