Dental prosthesis laboratories (DPLs) are among the workplaces where predominantly manual production takes place. In such working environments, during the manual manufacturing process, which involves fine smoothing and polishing of dental prostheses, fine particulate matter is released into the ambient air. In this study, the particulate matter (PM) concentrations and elemental content of the fine particles in the working ambient air were identified in six DPLs in Kocaeli, Turkey. PM(2.5)mass concentrations, measured in all the DPLs, ranged between 80.8 and 1645 mu g/m(3)(mean 414 +/- 406). As a result of the analyses performed with an ICP-MS device (Perkin Elmer Elan (R) DRC-e), trace elements of Be, Cd, Hg, and, notably, Co, Cr, Mo, and Ni were found. The researchers calculated the excess lifetime cancer risks and total hazard indexes. The average total cancer risk for all the DPLs was 8 x 10(-3), which is higher than the acceptable limit of 1.0 x 10(-6), and the total hazard index was 187, which is greater than the acceptable limit of 1.0. Considering these high-level risks, the study concluded that there is a need for new production methods, and strict application of occupational health and safety measures, to reduce the fine particle exposure of the workers in the laboratories. In addition, there are prescribed limit values for particulate matter only for respirable particles in working environments. The establishment of limit values, especially for PM(2.5)concentrations, is important for the protection of the health of the employees.