Re: alcohol stove fuel
Those "special additives" constitute less than 2% of the fuel. Most is plain old gasoline. The worst byproduct is carbon monoxide and it is very low. The average air on a boat is more than enough to never wory about it.
Some manufacturers use benzine, so you would not wash your hands with it, but once again, it is very safe to use as a fuel.
I spent many years with a class A chemical suit next to my desk as I was the one expected to rush in to take care of those who neglected safety precautions in my industry. I still have a current suit and gear here at the house. I guess old fire horses will always follow the bells.
The point is, Coleman fuel is made up of the pollutants that denatured alcohol has. If you can be safe with Coleman fuel or white gas then you will be safe with denatured alcohol.
As a side note, tha most dangerous chemical that I know of, the one that takes more lives than all of the others combined; quick and sudden or slow and painfull, is ordinary gasoline. If you can put it in your tank to get to work without worry then you can understand all other chemicals can be sucessfully dealt with with proper percautions. Some are not worth the risk for casual use, some are. Pays your money, place your bets.