The objectives of this study were to measure the concentrations of PAHs (polycyclic aromatic hydrocarbons) in three particle fractions [particulate matter (PM) PAHs (PAHcancer) in the two office environments. In the smokers’ office, PAHcancer levels fell by >70% during the weekend relative to working days, implying the importance of smoking and dust resuspension sources. The PMF model identified four contributory factors–sources: smoking, dust resuspension and two different vehicle-related sources. For 15 PAHs, the same factor made the largest contribution to both the PM1 and PM2.5 fractions, implying a common origin and further supporting the validity of the proposed approach. For the majority of the carcinogenic PAHs, smoking and dust resuspension made the strongest contribution (>90%) to both the PM1 and PM2.5 fractions. Although our PMF analysis confirmed the well-known contribution of smoking and traffic-related sources to levels of PAHs, the identification of dust resuspension as a separate source of PAHs is of great interest and requires further study.