As far as environmental problems there is no difference between the 3 in
terms of how much it would take to prevent freezing. Considering the amount
used, I see the automotive exhaust, especially with catalytic convertors,
which make the sulfur in your fuel into SO3, Sulfuric acid anhydride, about
which the EPA, when it became known that SO3 was produced by cats, said,
"There is NO evidence that SO3 is any more toxic than SO2...."

The vodka WILL rot your innards if you use enough of it. The only reason
isopropyl is any safer is that you puke it up quicker and it tastes REALLY bad.

Then there is calcium chloride, a GREAT anti-freeze. Don't let it in contact
with the metal on your car. I'm not sure it is of any benefit to the
environment, either. But if they didn't use it on the roads, you wouldn't
need nearly as much washer fluid!

Then how about the amount of rubber worn off your tires, the paint that erodes
off your finish, and the water with which you wash your car (or your engine!).

You remember Murphy's Law of Cleanliness: In order to get anything clean,
you must get something dirty. Corollary: You can get everything dirty
without getting anything clean.

One of the greatest characterized this as "straining at a gnat and swallowing
a camel".
--
George Downs Bartlesville, Heart of the USA!