Maternal transfer of contaminants: case study of the excretion of three polychlorinated biphenyl congeners and technical-grade endosulfan into eggs by white Leghorn chickens (Gallus domesticus).

Reported avian maternal transfer rates of organochlorine contaminants range from 1% to as much as 20% of maternal body burdens. However, to our knowledge, no investigation of factors governing maternal transfer has been reported. Here, we report an investigation of maternal transfer of 2,3,3',4,4'-pentachlorinated biphenyl (PCB 105), 2,3,3',4,4',5-hexachlorinated biphenyl (PCB 156), 2,3,3',4,4',5,5'-heptachlorinated biphenyl (PCB 189), and technical-grade endosulfan into eggs by white leghorn chickens (Gallus domesticus). Two experiments were performed to evaluate individual chemical excretion into eggs when hens were injected with each chemical individually (experiment one) or with a mixture of all four chemicals (experiment two). Each hen was injected subcutaneously every 4 d during a 21-d period with 100 microliters of the dosing solution during both experiments. The mass of each chemical excreted into the egg was compared among eggs and with the mass injected into hens to determine the influence of chemical structure (experiment one) and interaction (experiment two) on maternal transfer of those chemicals into eggs. Maternal transfer of PCBs was inversely related to congener chlorination. The congener mass in eggs, as a percentage of the mass injected into hens, was 0.42% for PCB 189, 0.54% for PCB 156, and 0.61% for PCB 105. In experiment two, absolute excretion of only PCB 189 and alpha-endosulfan into eggs was affected by the presence of other chemicals. Excretion of PCB 189 (0.51%) and alpha-endosulfan (0.03%) increased and decreased, respectively, compared with when they were individually injected into hens during experiment one. Lastly, much less of the more metabolically susceptible endosulfan (0.04-0.12% of the mass injected) was excreted into the egg relative to PCBs, despite being injected into the hens at concentrations comparable with those of PCBs, suggesting, at least in avian species, lower maternal transfer of more metabolically susceptible chemicals.