Electronic Cigarettes Emit Toxic Compounds, Several Factors Affect Chemical Concentrations

New research just published in the journal Environmental Science & Technology shows that electronic cigarettes emit harmful chemicals. Different factors affect the concentration of these emissions, including the age of the vaporizer and temperature. The study focused on two common solvents found in e-liquids, propylene glycol and glycerin. The findings may help companies develop safer devices.

A research team from Lawrence Berkeley National Laboratory emulated the vaping process by using three types of e-liquids and two different vaporizers in a custom-made apparatus. One of the e-cigarettes was a basic, inexpensive device while the other was a more expensive device with two heating coils.

The team found that both devices emitted toxic compounds, including two that hadn’t been recorded in past e-cigarette studies.  Significant concentrations of propylene oxide and glycidol were detected, both known as probable carcinogens. These compounds were emitted in the vapor of common e-liquid solvents, propylene glycol and glycerin. Both solvents are considered safe for use in food but there has been little research on the effects of inhaling the vapor of these chemicals.

Throughout the study, the researchers detected a total of 31 harmful compounds in e-liquid vapor. Temperature affected concentrations and emissions levels increased as the devices heated up with normal use. Voltage also mattered, partially because vapor temperature increases at higher voltages. For two of the harmful compounds, acrolein and formaldehyde, concentrations at a voltage of 4.8V were a full order of magnitude higher than concentrations formed at a low voltage of 3.3V. In addition, older devices emitted higher concentrations of toxic compounds. As a device is used over and over, polymerization byproducts build up near the coil. As the residues are heated up, they produce dangerous aldehydes.

E-cigarettes are still safer than traditional cigarettes. Both produce many of the same compounds but e-cigarettes emit smaller concentrations. It’s important to study these compounds when deciding how to regulate e-cigarettes, which have been steadily increasing in popularity. These findings could also be used to develop safer devices and less harmful solvents for e-liquids.


Mohamad Sleiman et al. Emissions from Electronic Cigarettes: Key Parameters Affecting the Release of Harmful Chemicals. Environmental Science & Technology (2016).

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