Advances in whole aerosol approaches for in vitro e-cigarette testing

Electronic-cigarette regulation and risk assessment is a prominent and developing field, as the popularity and prevalence of this product category increases. Over the last 10 years since their emergence, there have been many advances and adaptations to current in vitro testing techniques to better assess and predict absolute consumer risk. However, there are still requirements to create a cross-field harmonised approach to appropriate exposure and experimental design. With many assessments still being carried out using methods developed and optimised for cigarette smoke, there must first be an acknowledgement regarding the differences between cigarette smoke and tobacco-free e-cigarette aerosols before we can accurately assess these distinct products. Here, we discuss five published studies from within our own research to demonstrate how in vitro testing techniques have evolved to improve determination of risk by considering appropriate dosimetry and exposure for both e-cigarette and cigarette aerosols and how we can contextualise the data through human consumption and dose extrapolation, ultimately giving more relevance to in vitro data. Furthermore, we have demonstrated the evolution of techniques, which has allowed us to bridge between platforms, simplify exposure set-up, experimental design and demonstrate technology evolution within our products, thus fulfilling a responsible duty of care to consumers via an appropriate and robust in vitro product assessment.