Normal Vaping is Safe
There's two types of vaping, and e-cig device.
The first and original, was built for the purpose of atomising a nicotine carrier at the lowest possible temperature so it can be inhaled, because it was clear that the toxins produced in a cigarette were essentially a result of the higher burn temperature. Propylene glycol was used to achieve this vapour as it produces a smoke like stream at a lower temperature than that which generates a large number of toxins. These first-generation devices have been researched and the balance of evidence tells us that they either produce none, or greatly reduced levels of any of the toxins found in tobacco smoke (a few rogue ingredients occasionally found in cheap e-liquids not withstanding, as that is a separate issue).
Then as battery's became more powerful and cheaper, 'indie' companies and enthusiasts started modifying the electrical power that could be delivered to the atomiser. We started to see generation 2 devices that were able to deliver 10-15 watts or more to the heating element, elevating the temperature.
When this is combined particularly with 'dry wick' conditions, and especially when there is no e-juice feeding the atomiser, we have high enough temperatures to produce toxins known as carbonyls (also called reactive aldehydes). This is because, essentially, we have turned the low temperature, safe e-cigarette into something that is emulating the chemical environment in the tip of a burning cigarette. We can see that these generation 2 devices, when run incorrectly, are effectively a hybrid somewhere between cigarettes and conventional e-cigs.
As such these generation 2 devices need to be called something else. Perhaps 'high temp vaping' or 'hi-vaping' as opposed to just 'vaping', would be more informative for the media as terms to distinguish the devices and operating conditions that make these scenarios so different. It's like the difference between putting soup into a ceramic pottery oven and a slow cooker. The two are both electric, and use electricity. What you will get out of them are completely different because of operating temperatures. We dont confuse these ovens.
The bottom line - correctly used, low powered e-cigarettes were shown to NOT produce carbonyls or other toxins in the recent research the media has run with - so the evidence supporting them has grown, not diminished. For the higher power devices, the situation is different! See the letter causing the recent controversy (but vindicates conventional vaping) here
Dry puff and high power create temperatures that are too high - see here
"At low voltage (3.3 V), we did not detect the formation of any formaldehyde-releasing agents (estimated limit of detection, approximately 0.1 μg per 10 puffs). At high voltage (5.0 V), a mean (±SE) of 380±90 μg per sample (10 puffs) of formaldehyde was detected as formaldehyde-releasing agents."
This voltage corresponds to 14-16 watts, according to Dr Farsalinos;
"This means that at 5 volts the energy was around 14-16watts. That would be an extremely high value for most commercially-available atomizers (excluding some rebuildables which can withstand such high wattage levels)."