Characteristics of metallic nanoparticles emitted from heated Kanthal e-cigarette coils

Electronic (e-) cigarette use is becoming more common among youth and young adults. E-cigarette users may inhale metallic particles from the heating coil along with the nicotine vapor. This study aims to develop and validate an e-cigarette generation system for future inhalation toxicology studies of e-cigarettes by characterizing the size and number of metallic nanoparticles produced and their chemical compositions. An e-cigarette generation system was constructed and Kanthal A1 coils were tested without a nicotine solution and wick under operating conditions of varying coil resistance (0.1-1.0 Omega), applied power (10-70W), and duty cycle (5-50%). The size distribution and morphology of particles were characterized using a scanning mobility particle sizer and a transmission electron microscopy, respectively. The size of generated particles, as well as the number of particles generated, exhibited an increasing trend as the resistance of the coil increased. An initial large increase in size and number of particles generated was observed with increasing applied power, stabilizing with further increases in power. Increases in duty cycle resulted in increased particle generation. A similar pattern of particle generation was observed from the metal heating coils under various operating conditions. Under each operating condition, the number of generated particles exhibited a steep decrease during the first 15min of each test run. Our results show this e-cigarette generation system is useful for future research investigating the health impact of metallic particle inhalation on e-cigarette users.