Are e-cigarettes less harmful than regular cigarettes?

Yes—but that doesn’t mean e-cigarettes are safe. E-cigarette aerosol generally contains fewer toxic chemicals than the deadly mix of 7,000 chemicals in smoke from regular cigarettes.3 However, e-cigarette aerosol is not harmless. It can contain harmful and potentially harmful substances, including nicotine, heavy metals like lead, volatile organic compounds, and cancer-causing agents.

https://www.cdc.gov/tobacco/basic_information/e-cigarettes/about-e-cigarettes.html