This study measured particle size distributions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in two workplace atmospheres of the sintering grate and rough roll shredder in a sintering plant, and to assess their workers' health-related exposures. We found that the PCDD/F concentration of the sintering grate (site A=14.47 pg m(-3)) was lower than that of the rough roll shredder (site B=17.20 pg m(-3)). Particle size distributions of PCDD/Fs were in the form of the unimodal with the mass median aerodynamic diameter (MMAD) of 4.74 microm and 5.23 microm, and geometric standard deviation (sigma(g)) of 3.15 and 2.15 for the site A and B, respectively. The above results suggest that the workplace of the site A had a less fraction of coarse particles than that of the site B. The estimated PCDD/F concentrations of the inhalable fraction (11.0 pg m(-3)) and thoracic fraction (8.89 pg m(-3)) of the site A were lower than those of the site B (12.4 and 9.39 pg m(-3), respectively). But to the contrary the estimated respirable fraction of the site A (5.05 pg m(-3)) was slightly higher than that of the site B (4.93 pg m(-3)). Our results clearly indicate the importance to conduct particle size segregating samplings for assessing human PCDD/F exposures.