The purpose of the study is to assess whether employees of the Municipal Police Force of a big city exposed to urban pollution are at risk of hepatotoxicity. The usual clinical practice tests like AST, ALT, γ-GT, AP, conjugated and total bilirubin were carried out, accompanied by a questionnaire designed to identify the possible risk factors and the principal non-professional confounding factors for hepatotoxicity. The study covered 118 male Municipal Police employees performing traffic duties and 118 male blood donors engaged in office work. There were significant differences between exposed and controls with regard to the average AST and ALT values and values above the normal laboratory range; this was also the case for the distribution. The results suggest that there may be the possibility of liver damage among asymptomatic members of the Municipal Police Force and that periodic hepatic screening, with the above-mentioned tests, could be useful. It is presumed that chemical agents present in urban air in big cities may cause damage to the liver, even at exposure levels that fluctuate around the admissible environmental concentrations.