Sodium Nitrate (Saltpeter) has traditionally been added to cheeses, especially Dutch types, to eliminate late gassing from unwanted colifrorm and Clostridium bacteria. The actual inhibitor is Nitrite reduced from the Nitrate
FWIW - From Fundamentals Of Cheese Science page 211 - "NO2 (Nitrite) can also react with aromatic amino acids in cheese to produce nitrosamines, many of which are carcinogenic".