The relative contribution of individual polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzo-p-furans (PCDFs) to toxic equivalent values derived for bulked human adipose tissue samples from Wales, United Kingdom.

Five bulked human adipose tissue samples were analyzed for individual polychlorinated biphenyl (PCB) congeners (including selected non-ortho-substituted compounds) and polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). Mean PCB and PCDD/F (tetra-through octachlorinated homologues) concentrations were 0.75 g/g and 1.22 ng/g adipose tissue respectively. Both the congener patterns and levels detected were similar to those reported by laboratories in other industrialised countries. Each sample comprised of tissue taken from donors within a given locality. However, no obvious relationships were apparent between sampling area, absolute concentrations and congener pattern of PCBs and PCDD/Fs. The contribution of individual PCDD/F and non -ortho-(o), mono-o-, and di-o-substituted PCB congeners to the total calculated toxic equivalent values (TEQ) was assessed for each sample. The main contributions to the TEQ were the mono-o-substituted PCB congeners #118 (TEQ=42.5 pg/g of lipid), #156 (TEQ=24.8 pg/g) and #105 (TEQ=20.7 pg/g), followed by 1,2,3,6,7,8-HxCDD (TEQ=18.2 pg/g), 2,3,4,7,8-P5CDF (TEQ= 12 pg/g), 1,2,3,7,8-P5CDD (TEQ=11.5 pg/g), and the non-o-substituted PCB congener #126 (TEQ =11.3 pg/g). Collectively, these compounds accounted for 80% of the STEQ values. Based on the TEFs proposed by Safe (1990), the overall TEQs calculated for the monitored PCBs, were twice those due to PCDD/Fs