I helped few friends of mine quit smoking via vaping, hence have interest in the subject. To be honest, the heavy metal thing sounds bogus. The only metal part that is likely to be the donor is the heating element, which is usually made from stainless steel, nichrome or similar metal. Not seeing any "heavy" metals in the list. Furthermore the oxidation of the heating element with subsequent ejection of metal oxide will occur at elevated temperature, when heating element is not properly cooled by ejuice. If that happens you will have a mean dry hit and won't be able to actually vape with malfunctioning heating element like that.