I'm kind of disgruntled with the entire tobacco industry, myself. The nicotine from the electronic cigarettes are poorly adsorbed by the lungs, due to the composition of the base liquids. Most, though not all, occurs through the mucus membranes of the mouth, nose and sinuses.
If you're looking at problems, they are most likely to be in the flavorings. Buttery, creamy, and many sweet flavors work because they contain diacetyl. As the makers became aware of this, they substituted several other diketones. They may be just as bad.