In order to assess level of human exposure to nitrogen dioxide, 22 traffic police from the city of Rio de Janeiro were monitored during their working hours for 3 consecutive days. Samples were taken by using a passive sampler (badge) and analyzed spectrophotometrically after reacting with sulphanilic acid followed by coupling with N-naphtilethylenediamine dihydrochloride. Results ranged from 13.3 to 193.6 mg/m3. According to the literature, these levels are not associated with any acute damage to human health but care should be taken to avoid long-term problems.