Project Summary Electronic cigarettes (ECIGs) are a diverse class of products that use an electric heater to aerosolize a liquid often containing propylene glycol, vegetable glycerin, nicotine, and chemical flavorants. While the aerosol generated from ECIG use contains lower concentrations of some chemicals found in cigarette smoke, research has demonstrated that ECIG aerosol contains harmful irritants and toxicants including propylene glycol, vegetable glycerin, nicotine, volatile organic chemicals, formaldehyde, acetaldehyde, acrolein, furans, chloropropanols, and tobacco specific nitrosamines. Despite the presence of these compounds in ECIG aerosol, many ECIG users perceive that ECIG use is associated with low harm. As a result, indoor ECIG use around non-ECIG users, including ECIG use inside of vehicles, is common. Research has demonstrated that indoor ECIG use can result in secondhand and thirdhand exposure to chemicals present in ECIG aerosol, but research has yet to examine ECIG use inside of vehicles and if use in this small space results in increased exposures to ECIG generated chemicals. The specific aims of this project are to 1) examine self-reported ECIG use behaviors and perceptions regarding ECIG use inside of vehicles, 2) measure concentrations of chemicals deposited on interior surfaces inside of ECIG users’ vehicles who report ECIG use in their vehicles, and 3) measure particulate matter concentrations inside of ECIG users’ vehicles during active ECIG use. This study will use online survey methods to examine ECIG use behaviors inside of vehicles (e.g., prevalence of ECIG use in vehicles, ECIG use with others in the vehicle, ECIG use with windows up/down, etc.) in a sample of adult current ECIG users. Additionally, ECIG users who report ECIG use inside their vehicles will present for an in person visit with their vehicles. Participants will include users of “pod mod” ECIG devices and “third generation” ECIG devices as well as controls (i.e., non-ECIG users with vehicles where no ECIG or tobacco use occurs). Samples will be collected from the interior surfaces of ECIG users’ vehicles (and control vehicles) and chemical analyses will detect and quantify the presence of chemicals found in ECIG aerosol. ECIG users will then engage in active ECIG use inside of their vehicles including a 10-puff directed bout (one puff every 30 seconds) and 20 minutes where they engage in ECIG use ad libitum. During ECIG use sessions, particulate matter concentrations will be measured inside of the vehicles. Expected results include that ECIG use inside of vehicles will be common among ECIG users and will be associated with high concentrations of chemicals and particulate matter inside of vehicles. These data will increase understanding of the prevalence and types of ECIG use behaviors that occur inside of vehicles as well as the secondhand and thirdhand exposures associated with ECIG use within vehicles by different types of ECIG devices. Successful c...