There is a carcinogen that Glycerin turns into at VERY HIGH temps. I am sure this is what someone told him, I think it is in the FDA report. BUT, it requires something like 45degrees Kelvin, yes I just used Kelvin temp measure, and ATTYs only get to 250 degrees Fahrenheit, so you are about 600degrees short of what it takes for it to be bad for you.
The thing it burns into has been shown to increase the chances of cancer in lab rats when incinerated at higher that normally humanly possible temperatures.
you do know that sacarin, in diet soda causes cancer too right?
This was a hot topic a cpl of weeks ago on th forum, but I can't find the thread. We had a chemistry person talking about the fact that it WAS NOT POSSIBLE to get this reaction from ANY type of battery, or even a straight short, as you would need like however many thousands of volts of electricity to produce the amount of reaction necessary to create this carcinogen.