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 knowle dge, no investigation of factors governing maternal transfer has been repor ted. Here, we report an investigation of maternal transfer of 2,3,3',4,4'-p entachlorinated 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 techn ical-grade endosulfan into eggs by white leghorn chickens (Gallus domesticu s). Two experiments were performed to evaluate individual chemical excretio n into eggs when hens were injected with each chemical individually (experi ment one) or with a mixture of all four chemicals (experiment two). Each he n was injected subcutaneously every 4 d during a 21-d period with 100 mul o f the dosing solution during both experiments. The mass of each chemical ex creted 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 chlorinat ion. The congener mass in eggs, as a percentage of the mass injected into h ens, was 0.42% for PCB 189, 0.54% for PCB 156, and 0.61% for PCB 105. In ex periment 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, respectivel y, compared with when they were individually injected into hens during expe riment one. Lastly, much less of the more metabolically susceptible endosul fan (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 wi th those of PCBs, suggesting, at least in avian species, lower maternal tra nsfer of more metabolically susceptible chemicals.