Atmospheric pollution represents a relevant environmental hazard which has been associated with considerable excess mortality, morbidity, and increased rates of respiratory diseases in humans. To date, more than 3,000 environmental chemical compounds have been identified in the ambient atmosphere, including a variety of mutagenic and/or carcinogenic agents, such as polycyclic aromatic hydrocarbons (PAHs), aromatic amines, and heterocyclic compounds. Positive associations between cytogenetic markers and airborne levels of PAHs have been reported by experimental and human studies. Traffic has been implicated as the major determinant for the concentration of PAHs and, therefore, for the genotoxic activity of urban air. A biomonitoring study has been conducted in 82 italian traffic police workers exposed to air pollutants and 34 control subjects (matched by age, gender, and smoking habits) not exposed to traffic pollutants. The aim of this study was to assess the cytogenetic effects, such as micronucleus frequency in peripheral blood lymphocytes, and to estimate the association with individual exposure to PAH. Statistical analysis of the frequency of micronuclei in binucleated cells showed higher mean levels in referent subjects (4.03%) than in traffic police officers (3.73%). Smoking showed no effect on the frequency of micronuclei. The study failed to detect any association between micronucleus frequency and individual level of benzo(a)pyrene, considered a marker of exposure to PAHs. These findings indicate that exposure to urban air pollutants does not result in increased levels of micronuclei in peripheral white blood cells.