Improvement in dioxin analysis of human blood and their concentrations in blood of Yusho patients

Background and objective:

Over 35 years have passed since the Yusho incident. We have determined the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and non-ortho-coplanar polychlorinated biphenyls (Co-PCBs) in blood samples collected from Yusho patients to establish new criteria for Yusho. Considering the fact that the concentrations of PCDDs, PCDFs and Co-PCBs in the blood samples of about 300 Yusho patients living in Japan were scheduled for measurement in 2002, it was desirable to develop more effective methods to speed up the pretreatment procedure for blood samples. In this study, we improved a method that allows many blood samples to be treated in a short period with high reproducibility in comparison with the previously described method. Using our method, we measured the concentrations of PCDDs, PCDFs and Co-PCBs in blood collected from 279 Yusho patients in 2002 and 269 Yusho patients in 2003, and compared the results with those of 52 normal controls.

Methods:

The extraction procedure of PCDDs, PCDFs and Co-PCBs from the blood samples was simplified. Concentrations of the PCDDs, PCDFs and Co-PCBs were measured using high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) equipped with a solvent-cut large volume injection system.

Results and conclusion:

The lipid content and the concentration of each isomer of PCDDs, PCDFs and Co-PCBs in blood determined using the improved method were almost equal to those obtained by dioxin analysis organizations that used the conventional method to analyze the same blood samples. The improved method demonstrated high reproducibility based on experiments conducted using the same serum samples. These findings indicate that the improved method is essentially equivalent to the conventional method. From the concentrations of PCDDs, PCDFs and Co-PCBs in blood samples of Yusho patients measured by the improved method, it became clear that even now Yusho patients still have a much higher concentration of PCDFs in their blood than do unaffected people more than 35 years after the Yusho incident.