Sodium nitrite is used extensively in curing meat and meat products, particularly pork products such as ham, bacon, frankfurters, etc.  As an ingredient in curing brines, sodium nitrite acts as a color fixative and inhibits bacteria growth, including Clostridium botulinum, the source of the botulism toxin.  Certain fish and poultry products are also cured with brines containing sodium nitrite.  All food uses of sodium nitrite are strictly regulated by FDA and USDA.