edit: okay I misunderstood what everyone meant
Then again, so are CFCs, CO2, radioactive materials...
Just because some elements naturally occur on Earth doesn't mean we're completely insensitive to where they end up. (That said, I have no idea if atmospheric Aluminium is actually a problem or not.)
Obviously it requires a more scientific analysis but it does seem to me that burning a lot of shit on the atmosphere might be problematic.