Polychlorinated biphenyl congeners as markers of toxic equivalents of polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans in breast milk

In breast milk, concentrations of polychlorinated biphenyls (PCBs) are high er than those of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofuran s (PCDFs), making PCB analyses less time-consuming and expensive. We search ed for PCB "markers" of PCDD/DF concentrations, by studying associations be tween concentrations of PCB and PCDD/DFs (expressed as toxic equivalents, T EQs) in breast milk from 27 women (primiparas, 22-35 years). These women do nated breast milk in 1996-1999 together with 183 other primiparas from Upps ala County, Sweden. Regression analyses showed that both dioxin-like and no n-dioxin-like penta- to hepta-chlorinated PCBs could be used as markers of TEQ concentrations in this group of women, in some cases after age adjustme nt of the regressions. The strong positive association between concentratio ns of dioxin-like PCB/DD/DFs and non-dioxin-like PCBs will in future epidem iological studies make it difficult to separate Ah receptor-dependent effec ts from non-Ah receptor-dependent effects. With the use of regression equat ions and concentrations in breast milk samples collected in 1994, TEQ conce ntrations were estimated in the 1994 samples. Comparisons between estimated and measured concentrations indicated that associations between concentrat ions of marker substances and TEQs should be determined separately within e ach study population, in order to obtain reliable TEQ exposure assessments from PCB markers. (C) 2001 Academic Press.