Measuring transfer of 14C-PCB from maternal diet to milk in a goat model using an accelerator mass spectrometer (AMS)

Environmental pollutants pose a substantial risk to nursing infants. Many of these toxicants (i.e. PCBs, PBDEs, mercury) are passed from the maternal diet to the nursing infant in breast milk. Determining the toxicokinetics has been difficult to measure due to ethical limitations. Since extremely small amounts of C-14 can be measured using Accelerator Mass Spectrometry (AMS), a goat model was used to establish a minimum oral dose of C-14-labeled PCB (2,2',4,4',5,5'-hexachlorobiphenyl-UL-C-14) that could be given to a lactating animal and traced into the milk. An oral dose of 66 nCi/kg body weight (1.84 mu g PCB/kg bw) was administered. Plasma and milk samples were collected for 2 months after dosing. The concentration of 14C label reached a peak value of 1.71 ng/ml PCB equivalents in the milk on day 2 and then declined to about 135 pg/ml PCB equivalents in the milk at 3 weeks. A second goat was administered a smaller dose (22 nCi/kg bw; 616 ng PCB/kg bw). A peak concentration of 485 pg PCB equivalents/ml milk occurred at 3 days and declined to 77.6 pg PCB equivalents/ml milk by 3 weeks. Our results indicated that an even lower dosage of labeled-PCB could be used due to the extreme sensitivity of AMS measurement. Extrapolating from current data it is estimated that the dose could be reduced by a factor of 20 (31 ng PCB/kg bw; 1.1 nCi/kg bw) and still be detectable after 2 months. Thus, the potential exists for developing protocols for studying toxicokinetics in humans using radiologically- and toxicologically-benign doses of labeled environmental toxicants. (c) 2007 Elsevier B.V. All rights reserved.