The Drexel university medical school study results are in this link. It's the result of a study of thousands of vapers who participated over a 5 year period. The doctor who wrote the report comments in the report that he believes vapor is harmless to bystanders and adds that his findings were that all the components of ecig vapor are far below the levels considered safe by the EPA. Standing on a city street corner inhaling fumes from cars and buses may just be much more harmful to your health than vaping.
http://publichealth.drexel.edu/~/media/files/publichealth/ms08.pdf
To summarise that paper
Someone vaping 25ml/day of >50% PG juice will be exposed to potentially concerning levels of PG. (60% of the TLV for all non-specified organic vapours)
Shock of Shocks, anyone vaping a juice with a nic content is likely getting more than the TLV of nicotine.
Polycyclic Aromatic Hydrocarbons were found in the aerosol. Pyrene was the only PAH detected in one study. Pyrene is not carcinogenic.
Tobaccos Specific NitrsosAmines were present in >90% of liquids. Although they were in concentrations 1/1000 that found in SNUS. A daily dose of 25-50picograms was calucalted on worst case scenarios. This number is enough to warrant some caution but will likely decrease as nicotine manufacture improves. May warrant regulation/control.
Volatile Organic compounds;
Acrolein 2% of TLV across 150 measurements
Formaldehyde: 0-4% TLV
Both of the above come from one experiment where the atty was left running for a long time and atomizer, generating high concentration carbonyls, had been burned black
VOC except benzene, acetic acid and isoprene were all much below 1%TLV in exhaled vapor
DiEthylene Glycol was detected in anomalously high levels in one study, even at those levels <1%TLV exposure to vaper.
Metals, taking the worst case for each of the metals results in <1% TLV on worst case scenario assumptions about the form of these metals.
Conclusion
"By the standards of occupational hygiene, current data do not indicate that exposures to vapers from contaminants in electronic cigarettes warrant a concern. There are no known toxicological synergies among compounds in the aerosol, and mixture of the contaminants does not pose a risk to health. However, exposure of vapers to propylene glycol and glycerin reaches the levels at which, if one were considering the exposure in connection with a workplace setting, it would be prudent to scrutinize the health of exposed individuals and examine how exposures could be reduced. This is the basis for the recommendation to monitor levels and effects of prolonged exposure to propylene glycol and glycerin that comprise the bulk of emissions from electronic cigarettes other than nicotine and water vapor. From this perspective, and taking the analogy of work on theatrical fogs [45,46], it can be speculated that respiratory functions and symptoms (but not cancer of respiratory tract or non-malignant respiratory disease) of the vaper is of primary interest."
"The cautions about propylene glycol and glycerin apply only to the exposure experienced by the vapers themselves. Exposure of bystanders to the listed ingredients, let alone the contaminants, does not warrant a concern as the exposure is likely to be orders of magnitude lower than exposure experienced by vapers. Further research employing realistic conditions could help quantify the quantity of exhaled aerosol and its behavior in the environment under realistic worst-case scenarios (i.e., not small sealed chambers), but this is not a priority since the exposure experienced by bystanders is clearly very low compared to the exposure of vapers, and thus there is no reason to expect it would have any health effects."
"The only unintentional exposures (i.e., not the nicotine) that seem to rise to the level that they are worth further research are the carrier chemicals themselves, propylene glycol and glycerin. This exposure is not known to cause health problems, but the magnitude of the exposure is novel and thus is at the levels for concern based on the lack of reassuring data."