Nitrite: a co-carcinogen?

The concurrent administration of N-nitroso-N-methylbenzylamine (NMBA) (10 mg/l drinking water) and sodium nitrite (5 g or 1 g/kg basic diet) induces enhanced progression of esophageal tumors. Pathologic changes of the respiratory system, which do not occur with administration of NMBA alone, are also observed. These findings call for re-evaluation of the toxicological significance of nitrite.