Abstract
This study employed a newly developed MALDA-MOUDI approach to investigate the respiratory deposition of Electronic Nicotine Delivery Systems (ENDS) and Heated Tobacco Products (HTP) aerosols and used the resulting data to assess associated health risks. MALDA-MOUDI is a tandem system that integrates the Mobile Aerosol Lung Deposition Apparatus (MALDA) with the Micro-Orifice Uniform Deposit Impactor (MOUDI) to enable effective estimations of the size-dependent deposited mass of inhaled aerosol in major airway regions. The MALDA-MOUDI system covers a wide particle size range, from nanometers to micrometers, making it ideal for comprehensive aerosol exposure research. To study ENDS and HTP aerosol respiratory deposition using MALDA-MOUDI, a series of laboratory experiments were conducted to obtain the deposited mass of ENDS and HTP aerosol in human airways. Two types of ENDS and one HTP (JUUL, disposable, and IQOS) were used in the study to generate test aerosol. MALDA-MOUDI respiratory deposition experiments were carried out under both active (mainstream) and passive (secondhand) using conditions. Metal-induced health risks were systematically evaluated based on the measured respiratory deposited mass under presumed active and passive using scenarios. The acquired results indicated that non-cancer and cancer risks associated with metals released from the tested ENDS and HTP fell within acceptable levels for both active and passive using. The MALDA-MOUDI system is a valuable tool for aerosol respiratory deposition studies and can be applied to broader environmental and occupational aerosol exposure research to assess health risks associated with toxic substances in aerosol particles.