The job I'm on is starting to explore minimum quantity lubrication myself, having stumbled on MQL while trying to find out more about Datron's alcohol-based coolant. I have pretty much the same questions.
Kool Mist is relatively cheap. Its MSDS says it contains Tri-ethanolamine (TEA), ethylene glycol and propylene glycol, which are 'harmful if swallowed' and 'irritant'.
--T.E.A. (says wikipedia) is in sunscreen, laundry detergent, hand sanitizer, shaving cream and paint. It's not good for aquatic species, and mentioned in the UN Chemical Weapons Convention.
--Propylene glycol is the stuff in e-cigarettes that makes it smell sweet. It has a negative effect on the environment if dissolved in water because it reacts with dissolved oxygen, depriving fish.
--Ethylene glycol is basically the main ingredient in antifreeze(!). It is highly toxic but breaks down in the environment in about 10 days.