gunpowder, carcinogens, and bbq pork

My dad found a recipe for bbq pork that called for saltpeter as a curing agent. He had adventures trying to find the ingredient, and then he found warnings on the Internet that using it for food created carcinogens.

http://donpjones.wordpress.com/2010/03/28/post-15-lorraines-pork-roast/