There are also a handful of states where hydrocarbon refrigerants are banned for automotive use. The EPA site lists these. All I remember is that neither Missouri nor Illinois are on the list.

I've seen a video of the windows exploding out of a car, purporting to show just how dangerous hydrocarbons are to use in this application. I'm not sure that I believe the doom-and-gloom scenario; they probably had to be careful to be able to get the proper mix of hydrocarbons and air in the interior to make the effect (dramatic as it was).