Boiled linseed oil was made by oiling years ago to make raw linseed oil dry. It is no longer boiled but rather metallic dryers that are usually salts of cobalt, manganese or zinc are added to speed the curing. It is probably one of these or a resin in the oil that is the "California carcenogenic". Don't use either linseed oil for food contact.
My question is why anyone would use boiled linseed oil as a finish? Quoting from the best book available on the subject, Understanding Wood Finishing by Bob Flexner, "Of all finishes except wax, linseed oil is the least protective. It's a soft, thin finish, so it provides no significant barrier against scratching. It's also easily penetrated by water and water vapor. Liquid water will work through a linseed oil finish and cause a smudge within 5 to 10 seconds. Water vapor will pass through a linseed oil finish almost as if it wasn't there."
Gary, why are you using a linseed oil finish? If you say that it is historically accurate to a piece that you are working on, remember that it was not a good finish, just the best that was available many years ago.