Quantification of all 209 PCB congeners in blood-Can indicators be used to calculate the total PCB blood load?

Polychlorinated biphenyls (PCBs) are a substance group of 209 theoretically possible compounds. The human body burden of PCBs is commonly calculated based on so-called indicator congeners such as PCB 138, PCB 153 and PCB 180, which are analyzed in human blood. The German "Human Biomonitoring (HBM) Commission" assumes that the sum of these indicator congeners multiplied by a factor of 2 represents the total PCB burden. This norm is based on data obtained from exposure studies after dietary intake. Data from indoor air shows a different congener pattern, which might lead to a relatively higher intake of lower chlorinated PCBs by inhalation. In two independent studies with adult participants from two regions in Germany, we measured all 209 PCB congeners in 44 whole blood and 42 plasma samples. Participants from the whole blood study group had additional exposure to PCBs via indoor air. With our analytical method, 141 individual PCB congeners, 27 coeluted pairs of PCB congeners and 2 records of 3 and 4 coeluted PCBs could be determined. Thus, 172 analysis results were reported per sample. In the whole blood samples, 50 congeners showed values below the limit of quantification (LOQ), whereas 94 congeners could not be detected in any of plasma samples. Total PCB concentrations (Σ 209 PCB congeners, incl. ½ LOQ) in the whole blood samples ranged from 99 to 2152ng PCB/g lipid (Median: 454ng/g lipid; 95th Percentile: 1404ng/g lipid). The sum of all 209 measured PCB (incl. ½ LOQ) in plasma samples showed levels between 52 and 933ng PCB/g lipid (Median: 226ng/g lipid; 95th Percentile: 642ng/g lipid). Our results show that the burden of PCBs on the human body is caused mainly by the three highly chlorinated indicator congeners PCB 138, PCB 153 and PCB 180. In median approximately 50% of the total PCB content in human whole blood or plasma samples can be attributed to these congeners. Total PCB, calculated by multiplying the sum of the three indicator congeners by 2, showed a strong and highly significant correlation to the sum of all 209 measured congeners for each sample. A slightly stronger correlation in the whole blood samples could be achieved by choosing six indicator congeners, including the lower chlorinated congeners (PCB 28, 52 and 101) into the calculation. Although this difference is very small, it must be considered that higher PCB levels in indoor air than those measured in the present study might be associated with a higher burden of indoor-air-related congeners in exposed individuals. For precautionary reasons, it could therefore be recommended that the assessment of individuals exposed to PCB via indoor air should be carried out based on the sum of the 6 indicator congeners PCB 28, PCB 52, PCB 101, PCB 138, PCB 153 and PCB 180 multiplied by a factor of 2.