We cannot afford to go backwards on pollution and climate change.  While researching artistic information on heavy metals and metalpoint, came across what lead and leaded gasolines really did to us.  And our environment.  We cannot pretend ignorance or that we haven't already "been there, done that".  

Heavy Metals at Wikipedia

See paragraph 3 under toxicity

"Key No.3"  pewter (tin, copper, antimony) (c) laeom