Aerosol Heat and Mass Transfer in The Regulatory Science of Emerging Tobacco Products

Abstract

For decades, the tobacco industry has manipulated the sensory characteristics of tobacco products including the degree of harshness experienced at the back of the throat. Commonly referred to as “throat hit”, this harshness derives from absorption of gas-phase nicotine by the sensory nerves. Users learn to associate throat hit with the positive psychological effects of nicotine, making throat hit a secondary reinforcer for smoking. On the other hand, throat hit can make products aversive to nicotine naïve users and can mediate inhalation patterns. In recent years, ENDS manufacturers have increased nicotine content and lowered the freebase nicotine fraction of their products, making products that can deliver palatably a high nicotine dose. In this study we developed a simplified computational model of the heat and mass transfer processes for a nicotine-containing aerosol generated by an ENDS device of given power and liquid composition flowing through the mouth and throat. We compared computed nicotine absorption in the throat to reported subjective effects from previous clinical studies conducted by our group. Across various ENDS configurations, we found that computed nicotine absorption in the upper airways strongly predicted subjective harshness scores (r=0.58; p<0.0001). This finding indicates the technical feasibility of making ENDS throat hit a regulatory target, i.e. to reduce product appeal to prospective nicotine naïve users. In addition, this work comprises three additional studies directed at assessing toxicant origins, mouth level emissions, and nicotine emission rates of novel tobacco products.