JUUL (or pod-based e-cigs) can deliver more nicotine than a cigarette.
Stella Juhyun Lee, PhD1; Vaughan W. Rees, PhD2; Noam Yossefy, MPH2; et al. (2020, June 1). Youth and Young Adult Use of Pod-Based Electronic Cigarettes From 2015 to 2019. Retrieved from https://jamanetwork.com/journals/jamapediatrics/article-abstract/2766303.
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