Some studies have found vapes to contain lead, nickel, tin, silver, formaldehyde, manganese, toluene, and other chemicals linked to cancer and central nervous system problems.
Williams, M., Villarreal, A., Bozhilov, K., Lin, S., & Talbot, P. (n.d.). Metal and silicate particles including nanoparticles are present in electronic cigarette cartomizer fluid and aerosol. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/23526962
Metal Concentrations in e-Cigarette Liquid and Aerosol Samples: The Contribution of Metallic Coils. (n.d.). Retrieved from https://ehp.niehs.nih.gov/doi/10.1289/ehp2175