Toxins In Vapor From Electronic Cigarettes Can Travel Far Interview with:
Uploaded by Merak MareyJonathan Thornburg, PhD
Director, Exposure and Aerosol Technology
RTI International
Research Triangle Park, NC

MedicalResearch: What is the background for this study? What are the main findings?

Dr. Thornburg: RTI wants to improve the human condition by protecting public health from exposure to contaminants. That includes secondhand exposure to electronic cigarette vapors. RTI realized that most research has focused on the electronic cigarette user, not on secondhand exposure. Our research created a simulated lung in our laboratory to produce representative electronic cigarette aerosol that a user would exhale so we could measure the aerosol size distribution and chemical composition. Those two parameters are critical characteristics for understanding the physical and chemical properties of the aerosol as it disperses in the environment to produce the airborne concentrations that determine someone’s secondhand exposure. Our main findings were:

  1. The aerosol particles exhaled by a user are smaller than 1000 nm, with median size between 100 and 200 nm. The aerosol size distribution varies with the type of e-liquid used.
  2. The aerosol is made of water, glycerin/propylene glycol, nicotine, artificial flavors, and preservatives
  3. Artificial flavors identified were ethyl maltol, 2-methyl naphthalene and 2-tert-butyl-p-cresol present.
  4. BHA and BHT preservatives were present.
  5. Dosimetry modeling determined that more than 50% of the electronic cigarette emissions were exhaled by the user, potentially leading to secondhand exposure.

MedicalResearch: What should clinicians and patients take away from your report?

Dr. Thornburg: That exhaled electronic cigarette vapors contain particles of small size that can travel far distances within buildings and outdoors. They travel much farther than the point where the “white cloud” exhaled by the user disappears. The size of these particles,  less than 1000 nm, will penetrate the alveolar region of a person’s lungs.  The particles contain flavorings and preservatives that are “generally regarded as safe” as a food additive. No one knows how safe these chemicals are if they are inhaled.

MedicalResearch: What recommendations do you have for future research as a result of this study?

Dr. Thornburg: Future research should incorporate an integrated program that synergistically addresses
1) characterization of the physical and chemical properties of the electronic cigarette emissions,
2) the toxicity of the emissions,
3) secondhand exposure measurements, and 4) acute respiratory changes, such as asthma, that result from inhaling electronic cigarette emissions.


Jonathan Thornburg, Quentin Malloy, Seung-Hyun Cho, William Studabaker, and Youn Ok Lee. Exhaled Electronic Cigarette Emissions: What’s Your Secondhand Exposure? RTI Press, March 2015 DOI: 10.3768/rtipress.2015.rb.0008.1503

Jonathan Thornburg, PhD, Director, Exposure and Aerosol Technology (2015). Toxins In Vapor From Electronic Cigarettes Can Travel Far