Dynamic Chemistry and Toxicity of E-Cigarette Aerosols and Their Product Waste

The rapid rise of e-cigarette (vape) use over the past decade has raised significant public health and environmental concerns. While marketed as safer alternatives to combustible cigarettes, e-cigarettes generate complex aerosols that expose both users and nonusers to potentially harmful compounds. Vaping produces aerosols containing active ingredients (such as nicotine or cannabinoids), flavoring agents, metals, carbonyls, reactive oxygen species, and ultrafine particles that can deposit throughout the respiratory tract. Beyond direct inhalation, nonusers are also subject to secondhand and thirdhand exposure through inhalation of exhaled aerosols and contact with surface-deposited residues. These aerosols undergo dynamic physicochemical transformations, including gas-particle partitioning, oxidation, and aging processes, that may enhance their toxicity by increasing the abundance of reactive and oxygenated species. Emerging evidence suggests that passive exposure may pose disproportionate risks to vulnerable populations, such as children, adolescents, pregnant women, and the elderly. In addition, the rapid expansion of disposable e-cigarette products introduces new environmental hazards. Improper disposal of devices containing plastics, metals, lithium batteries, and residual e-liquids contributes to electronic waste, microplastic pollution, and leaching of toxicants, such as nicotine, heavy metals, and persistent organic pollutants. Despite growing research, critical gaps remain in understanding the long-term health effects of passive vaping, the environmental transformation of e-cigarette emissions, and the ecological consequences of disposable device waste. This review highlights current evidence on the composition, transformation, and toxicity of e-cigarette aerosols, examines the environmental burden of e-cigarette waste, and outlines future research priorities needed to inform regulatory policies and protect public health.