Well, is there anything in life that is perfectly safe?
No, but that statement is too broad to apply to everything as a rationalization for doing it.
The problem is we are dealing with a lot of unknowns. We don't have long term medical surveillance, vendors don't fully disclose or even know themselves what the materials in their products result in after thermal decomposition and there are no immediate effects or evidence that makes the assessment clear. And a lot of these products come from a country with few controls in place that would otherwise enforce more vigorous consumer protections, and in the name of free trade, we bring these products into our consumer cycle with little oversight (at this point).
I work in the fire service. I teach the chemistry of pyrolysis and hazardous materials. I actively firefight and I wear and service SCBA (self contained breathing apparatus) and I observe and am exposed to a lot of their byproducts.
One thing I am very aware of is respiratory protection as it pertains to byproducts of combustion and byproducts of incomplete combustion. What we have learned in the last five years is that incomplete combustion is far worse than we ever thought. And while we believe vaping is a non-combustion process, I can tell you as someone with *some* expertise in fire science, that when an atomizer leaves charring, an incomplete combustion process has occurred. Thermal decomposition is extremely complex as its input are analog processes - random quantities of heat, oxygen, reducing agents, their ignition temperatures and their chemistry all change under their unique conditions. That's why no two fires are alike. Even the thermal cooling influence of juice on coil affects the results.
If I put on an arson investigators hat and looked at that photo I can tell you there was a high heat source with direct contact to that material, and the missing material was consumed (the reducing agent) and underwent thermal decomposition. Those same patterns in the picture I posted are the same kinds of things we see on furnishings after a fire.
Thermal decomposition produces smoke and smoke is toxic by its nature. It contains aerosols, particulates and gases, even if it is in minute quantities. Worse, it is now suspended in a vapor so as to be undetectable. Short of some extremely complex and expensive analysis, you really don't know what is going up the chimney of an atomizer.
What you can look at is the condition of the reducing agents (wick, coil and char and residue) and make some educated guesses about what might be in it, which is why I take apart atomizers after using them and assess if a combustion process has occurred - that evidence IF present is undeniable.
So, where do we go from here?
Its about personal risk assessment. Gather the information you can. Research as much as you can and be informed as you can about the processes involved and then decide risk versus reward. Nothing is risk free however, some things are clearly more risky than others and that's what makes it a personal decision.
Subohming introduces far more risk because the temperatures create radiant and contact energies high enough to result in thermal decomposition and that is an alarm bell that we should ALL be aware of.
One example from the fire service I can give you. For years we thought just man-made materials gave off toxic byproducts. We have now discovered that even a bale of hay produces hydrogen cyanide (H2S) in varying quantities - we were all shocked by this and the service has now been introducing air monitoring programs at fires to look for this. Hydrogen cyanide and carbon monoxide (CO - also called when together the "evil twins") are found in organic-only (ordinary combustible class A) fires and are a health risk if inhaled. Hydrogen cyanide attacks muscle tissue and particularly heart muscle. Carbon monoxide bonds with hemoglobin and prevents the transfer of oxygen to the cells in your body. It is now understood firefighters who die from heart attacks, hours or days later after a big fire may actually have been poisoned from these two byproducts. (Reference:
http://www.montanafirechiefs.com/Assets/dept_1/PM/pdf/Toxic Byproducts of Combustion.ppt - Slide 51 in particular)
Sorry, its a long post but I wanted to brain dump this to put the picture into the context as I see it. You're welcome to whatever conclusions you want to make yourselves, but that's mine.
