WPA bans Argon. Only problem is that Argon is the third most common substance constituting 1% of the atmosphere

Observers speculate that activists handed EPA a list and they rubber stamped without doing any thinking. Because Argon is a noble gas that like helium doesn't react with other elements making it a strange substance to be dangerous.  Not to mention we breath huge amounts if it every day.

http://wattsupwiththat.com/2014/10/29/the-epa-jumps-the-shark-banning-argon/