The aim of present study was to evaluate whether traffic policemen exposed to urban pollutants and possible psycho-social stressors are at risk of alterations on plasma growth hormone (GH) levels compared with a control group. Out of a population of 395 Municipal Police employees, the subjects with principal confounding factors were excluded from the study. The remaining traffic policemen were matched with those not exposed by sex, age, working life, and habitual consumption of alcohol; 71 traffic policemen (40 men and 31 women) with outdoor activity exposed to urban pollutants and 71 not exposed subjects (40 men and 31 women) with indoor activity were included in the study. The plasma levels of GH were significantly lower in the exposed traffic policemen compared with those not exposed (P = 0.000); similarly in male (P = 0.011) and female subjects (P = 0.000). The authors hypothesize the possibility of an effect of the specific working activity in traffic policemen on the plasma GH concentrations.