Nitric monooxide (NO) and nitric oxides (NOx) are the dangerous air pollutants possessing high nitrosative and genotoxic potential with adverse health effects. Environmental NO is related to nitrosative stress development in human body. Overproduction of NO has been implicated as a pathological factor in several forms of chronic human diseases, including cancer. The aim of this study was to evaluate exposure and risk associated with exogenic NOx impact on the growth of model tumor Guerin's carcinoma (GC), xanthine oxidoreductase (XOR) activity, levels of mobile lipid domens (MLD), functional activity of peritoneal macrophages (PM) and lipid peroxidation (LPO) in tumor tissue. Exogenous NOx inhalation leads to nitrosative stress development and toxic effect on cells of immune system in vivo. Tumor growth was accompanied by activation of PM. The prolonged inhalation of exogenous NOx caused hyperactivation of PM (4.9-fold), increased MLD formation and total XOR activity (1.6-fold), and accompanied by accelerated tumor growth. In paralel observed sharp decrease (2.4-fold) of xanthine oxidase (XO) activity and LPO level (3.5-fold). The ratio of XOR isoforms increased by 18-fold mainly due to inactivation of xanthine dehydrogenase form (XDH). Reverse correlation was observed between the considerable increase of XOR activity in tumors and decline of GC nodes sizes. The high activity of enzyme in tumor tissues was accompanied by a 3.8-fold decrease in a final size of GC nodes as compared to tumors with lower activity of XOR.