A couple of thoughts here - I think it is the acidity of beverages that leach the lead from crystal, not the alcohol. I don't know what the acidity of bourbon is compared to, say, wine. There certainly are organic acids. somePerhaps chemistry professor Tim can adddress this.Note re decanters: if you're going to use it for spirits, make sure the decanter is glass and not lead crystal. The high concentration of alcohol in spirits leaches the lead out of crystal.
If you don't store whiskey in leaded crystal, but just decant for serving, it shouldn't be a problem, according to the sources I've read for years, and which can be Googled.