Dr. Mike and those suspecting PG in the formation of formaldehyde appear to be wrong. The particular study mentioned here does not specify the specific makeup (or PG versus glycerin content) of the liquids studied.
BUT, many of the same authors are presenting a paper at the SRNT meeting in Boston this week that DOES. And from the following it is pretty clear that indeed it is glycerin, and not PG, that is associated with formaldhyde (and acrolein) being found in vapor:
SUBSTANTIAL REDUCTION IN EMISSION OF SELECTED CARBONYLS
AND VOLATILE ORGANIC COMPOUNDS FROM ELECTRONIC CIGARETTES
COMPARED TO TOBACCO CIGARETTES
Andrzej Sobczak, Ph.D.*1,2, Leon Kosmider1,2, Maciej L. Goniewicz, Ph.D.3,4, Jakub
Knysak2, Marzena Zaciera, Ph.D.5, and Jolanta Kurek5, 1Institute of Occupational
Medicine and Environmental Health, Sosnowiec, Poland; 2Medical University
of Silesia, Katowice, Poland;3Queen Mary University of London, UK; 4Roswell
Park Cancer Institute, Buffalo, USA; 5Institute of Occupational Medicine and
Environmental Health, Sosnowiec, Poland
Significance: Electronic cigarettes (ECs) are purported to deliver nicotine vapor
without any toxic substances generated from tobacco combustion. However, using
ECs involves heating a nicotine solution to high temperatures. This may induce
chemical reactions which result in the possible formation of carbonyl compounds
(CCs) and volatile organic compounds (VOCs). Many CCs and VOCs are common
tobacco-specific toxicants with proven carcinogenic and cardiotoxic properties. Aim
of the study:The aim of the study was to quantify and compare the levels of selected
CCs (formaldehyde, acetaldehyde, acrolein, acetone, propanal, butanal) and VOCs
(benzene, toluene, etylobenzene and ortho-, meta-, para-xylene) in EC nicotine
refill solutions, vapors generated from ECs,and mainstream smoke from tobacco
cigarettes. Methods: Six commercially available nicotine refill solutions for ECs
(Chic Group Ltd. Poland) were examined. Three solutions contained a mixture of
propylene glycol and glycerin (Volish brand) as a solvent for nicotine, while the
other three contained only propylene glycol (Mild brand). Thirtypuffs were taken
using an automatic smoking machine. Mainstream smoke was generated from
a3R4F reference tobacco cigarette. CCs were extracted from vapor and smoke to
solid phase with 2,4-dinitrophenylhydrazine, and analyzed using HPLC/DAD. VOCs
were absorbed on activated carbon and analyzed with GC/MS. Results:Traces of
acetaldehyde were detected in all examined EC solutions(0.081±0.042 μg/mL).
Acetaldehyde was found in all EC vapors (0.153±0.116 μg/30 puffs), but at levels
more than a thousand-fold lower than in tobacco smoke. Formaldehyde and acrolein
were only found in vapors generated from glycerin-based solutions (0.116±0.022
and0.110±0.190μg/30 puffs) and in tobacco smoke (12 and 32-fold higher levels,
respectively). None of the examined VOCs were detected in the vapors, while all
were found in tobacco smoke. Conclusions: In contrast to tobacco smoke, the
vapors generated from ECs does not contain VOCs. Exposure to CCs from ECs is
significantly reduced compared to tobacco smoke and may be attributable to the
glycerin content in the nicotine refill solution.