While e-cigarettes do not contain smoke, they do expose others to secondhand emissions. Little is known about these emissions or the potential harm they can cause. Two studies have found formaldehyde, benzene and tobacco-specific nitrosamines (all carcinogens) coming from those secondhand emissions. Other studies have shown that chemicals in the vapor contain formaldehyde, acetaldehyde and other potential toxins. There is no evidence that shows e-cigarettes emissions (secondhand aerosol) are safe for non-users to inhale.