The effect of hose permeability on toxicant yields for the narghile waterpipe is investigated, with special reference to the recent adoption of plastic as a hose construction material. Measurements of air infiltration rates for 23 leather and plastic hoses representing 11 types commonly available in Beirut, Lebanon were made, revealing that while leather hoses allowed significant outside air infiltration during a puff constituting up to 31% of the puff volume, plastic hoses were found to be air-tight, indicating that the smoke reaching the waterpipe user can be considerably more concentrated when delivered via a plastic hose. Total particulate matter (TPM), nicotine and carbon monoxide (CO) yields were compared when a waterpipe was machine smoked using a highly permeable leather and an air-tight plastic hose. It was found that the plastic hose resulted in similar yields of nicotine, but more than double the CO yielded with the highly permeable leather hose. Thus, even if narghile smokers titrate for nicotine intake, the use of a plastic hose will likely greatly increase the exposure to CO, a major causative agent in cardiovascular disease.