The aim of this study is to evaluate if the occupational exposure to urban stressor could cause alterations in dopamine (DA) plasma levels and related diseases in traffic police officers compared to a control group. After excluding subjects with principal confounding factors, 306 traffic police officers (139 female and 167 male) and 301 controls (134 female and 167 male) were included in the study. In traffic police officers, mean DA values were significantly higher compared with controls (P = 0.006 and P = 0.000 in male and female, respectively). The distribution of DA values in traffic police officers and controls was significant (P = 0.000 and P = 0.000 in male and female, respectively). The number of male traffic police officers with a positive response to the questionnaire's items concerning anxiety, depression and panic attacks was higher than controls, though not significant (7.2% traffic police officers versus 4.2% controls). This difference was also not significant in female traffic police officers compared with controls. According to our previous researches on other neuro-immune-endocrine parameters, DA could be used as an early biological marker, valuable for the group to be employed in occupational sets, even before the onset of pathology.