A Practical Framework for Novel Electronic Nicotine Delivery System Evaluation: Chemical and Toxicological Characterization of JUUL2 Aerosol and Comparison with Reference Cigarettes.

Electronic nicotine delivery systems (ENDSs) are designed as a non-combustible alternative to cigarettes, aiming to deliver nicotine without the harmful byproducts of tobacco combustion. As the category evolves and new ENDS products emerge, it is important to continually assess the levels of toxicologically relevant chemicals in the aerosols and characterize any related toxicology. Herein, we present a proposed framework for characterizing novel ENDS products (i.e., devices and formulations) and determining the reduced risk potential utilizing analytical chemistry and in vitro toxicological studies with a qualitative risk assessment. To demonstrate this proposed framework, long-term stability studies (12 months) analyzing relevant toxicant emissions from six formulations of a next-generation product, JUUL2, were conducted and compared to reference combustible cigarette (CC) smoke under both non-intense and intense puffing regimes. In addition, in vitro cytotoxicity, mutagenicity, and genotoxicity assays were conducted on aerosol and smoke condensates. In all samples, relevant toxicants under both non-intense and intense puffing regimes were substantially lower than those observed in reference CC smoke. Furthermore, neither cytotoxicity, mutagenicity, nor genotoxicity was observed in aerosol condensates generated under both intense and non-intense puffing regimes, in contrast to results observed for reference cigarettes. Following the proposed framework, the results demonstrate that the ENDS products studied in this work generate significantly lower levels of toxicants relative to reference cigarettes and were not cytotoxic, mutagenic, or genotoxic under these in vitro assay conditions.

Determination of chemical constituent yields in e-cigarette aerosol using partial and whole pod collections, a comparative analysis.

Literature reports the chemical constituent yields of electronic nicotine delivery systems (ENDS) aerosol collected using a range of aerosol collection strategies. The number of puffs to deplete an ENDS product varies widely, but collections often consist of data from the first 50-100 puffs. However, it is not clear whether these discrete puff blocks are representative of constituent yields over the life of a pod. We aimed to assess the effect of differing aerosol collection strategies on reported yields for select chemical constituents in the aerosol of closed pod-based ENDS products. Constituents analyzed were chosen to reflect important classes of compounds from the Final Premarket Tobacco Product Application Guidance. Yields were normalized to total device mass loss (DML). Collection strategies that consisted of partial pod collection were valid for determining yields of constituents whose DML normalized yields were consistent for the duration of pod life. These included primary aerosol constituents, such as propylene glycol, glycerol, and nicotine, and whole pod yields could be determined from initial puff blocks. However, changes were observed in the yields of some metals, some carbonyl compounds, and glycidol over pod life in a chemical constituent and product dependent manner. These results suggest that collection strategies consisting of initial puff block collections require validation per chemical constituent/product and are not appropriate for chemical constituents with variable yields over pod life. Whole pod collection increased sensitivity and accuracy in determining metal, carbonyl, and glycidol yields compared to puff block-based collection methodologies for all products tested.

Nanomechanical Filler Functionality Enables Ultralow Wear Polytetrafluoroethylene Composites.

Surprisingly, certain α-phase alumina filler particles at one to five weight percent can reduce the wear rate of polytetrafluoroethylene (PTFE) by 10,000 times, while other, seemingly comparable α-phase alumina particles provide only modest─by PTFE composite standards─100 times improvements. Detailed studies reveal that size, porosity, and composition of the particles play important roles, but a quantitative metric to support this mechanism is yet to be developed. We discovered the mechanistic importance of friability of the particles, for example, the ability of the particles to fragment at the sliding interface. This work establishes the importance of functionally friable metal-oxide filler particles in creating ultralow wear PTFE-metal-oxide composite systems. We used in situ nanoindentation/electron microscopy experiments to characterize the fracturability of candidate filler particles. A mechanistic framework relating apparent particle fracture toughness and wear is established, where porous low-apparent fracture toughness particles were observed to promote ultralow wear by breaking up during sliding and forming a thin, robust tribofilm, while dense, high-apparent fracture toughness particles abrade the countersurface, limiting the formation of ultralow wear promoting tribofilms. This framework enables use of a new metric to select filler particles for multifunctional, ultralow wear PTFE composites without relying solely on empirical tribological tests of polymer composite materials.