Abstract
This study aimed at clarifying patterns of serum concentrations of dioxins in the employees who worked for a waste incineration plant and at estimating elimination rates and half-lives of serum dioxin isomers, and maximum serum concentrations of dioxin isomers at a time of plant shut-down. Sixteen subjects participating 3 times or more during an 8-yr period from 2000 to 2007 were recruited for this study. Serum concentrations of dioxins expressed as TEQ/g-lipid decreased gradually after the plant shut-down, and the decrease was in the order of PCDFs, PCDDs and coplanar-PCBs. The serum TEQ concentrations of PCDF and PCDD congeners in the employees were higher than those in the general population surveyed by Ministry of the Environment, Japan, whereas the serum concentrations of coplanar-PCBs were similar to those in the general population. The estimated half-lives and elimination rates of PCDDs and PCDFs in the highly exposed workers increased compared to the moderately exposed workers. Estimated geometric mean serum concentrations of PCDDs, PCDFs and total dioxins at the time of plant shut-down were 35, 53 and 107 pg TEQ/g-lipid, respectively. These findings suggest that the ex-employees were occupationally exposed to dioxins in the waste incineration plant.
