There's not a hint of metal anywhere on my grinder after much use. It must just be the one you own.

Also chances are the wood used to make your wooden grinder has been chemically treated when the wood was being dried, and to make it last longer - wetting agent, dry-aid, varnish, formaldehyde, sodium benzoate, etc.

Also, a lighter never gets hot enough to sublimate aluminum or steel. It's impossible to inhale any vapor from thier use.

Look around your house. Your cookware, parts fo the element on your stove, the element in your kettle. They are all made from steel. There is a reason for this - it is inert and under operating temperatures do not get hot enough to sublimate gaseous metal - and thats based on real life scientific application, not stoner psuedo-knowledge.