Toluene is a carcinogen, but its also a pretty major part of pump fuel. You can add xylene (also not good for you) you can find both in cellulose thinners, which is used in spraying - so you've already breathed in a load of finely atomised carcinogens, and who knows you might well have drunk coffee as well (it contains over 200 toxins many of which are carcinogens as well!), oh and they've only just stopped putting Benzoic acid in soy sause
I've used non-blooming thinners mixed with the fuel in my S14, but I'm not convinced that it made much of a difference it may have knocked up the octane rating a few points, but its not any cheaper than running optimax.
The problem with funny fuels is the oil contamination, Nitromethane burns and forms Nitric acid - I used to get nose bleeds when I was working at Santa pod and the Funny Cars were on. You'd not want Nitric acid sitting in your engine (which is party why they strip the engines after each run).
Alcohol has a lower calorific value than gasoline, so you have to run almost twice as much and eliminate any components in your fuel system that may rust, as it absorbs water. If you use Methanol (over Ethanol) you'll have to consider the effect it has on your rubber components as it eats rubber on contact.
Propane is clean burning and has a very high octane (around about 120 IIRC), but you have problems with the storage. Its the best bet for clean power.
There is one other alternative that I've heard of a substance called d-limonene, which I wont go into here because you'll think I'm taking the piss. Suffice to say that its biologically sound, and is around 140octane.
Rob