Waterpipe tobacco smoke toxicity: the impact of waterpipe size

Introduction: Waterpipe tobacco smoking continues to show increasing popularity, especially among individuals between 18 and 22 years old. Waterpipe tobacco smoke (WTS) is a mixture of particulates and gases formed from the combustion of the charcoal and volatilisation and humidification of the tobacco+humectant+flavouring substrate known as shisha or mu'assel. As such, variation in the configuration of the waterpipe may affect the particles produced. Our study focuses on the effects of waterpipe size on the physical properties and cytotoxicity of the smoke produced.

Methods: Shisha type and headspace volume were held constant and a modified Beirut puff protocol was followed while the size of the waterpipe was varied. Particle concentrations and size distributions were measured using a TSI Engine Exhaust Particle Sizer. Type II alveolar cells were exposed to smoke at the air-liquid interface and two metrics of cell health analysed.

Results: In a 30 min session, we observed a decrease in total particle concentration (10¹⁴-10¹³) and mass (10 000-2800 mg/m³) and an increase in particle size (125-170 nm) as pipe height increases from 22 to 55 cm and bowl size from 300 to 1250 mL. Smoke from all pipe sizes caused decreases in lysosomal function (>40%) and membrane integrity (>60%) 24 hours post 57 min exposure, and meet the National Institutes of Health definition of a cytotoxic agent (≥30% decrease in cell viability).

Conclusion: Smoke from waterpipes of all sizes causes significant alveolar cellular harm, indicating that this device needs regulation as a hazard to human health.