To assess toxicokinetics of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), oral intake and fecal excretion were measured in two breast-fed infants and one formula-fed infant during the 1st y of life. The intake of these compounds was up to 50 times higher in the breast-fed infants. In these children, fecal excretion of the main tetra- to hexachlorinated congeners was less than 9% of the intake at age of 1 and 5 mo, indicating almost complete intestinal absorption during breast-feeding. In contrast, distinctly higher fecal excretion rates were observed for the hepta- and octachlorinated compounds. Despite much lower PCDD/PCDF intake after weaning, concentrations in stool fat did not decrease substantially. We conclude that concentrations in fecal fat more or less reflect those in body fat. Additionally, PCDD/PCDF concentrations were measured in blood fat of all infants (and in a second formula-fed baby) at the age of 11 mo. International toxicity equivalent (I-TEq) concentrations in the formula-fed infants were less than 25% of maternal values and about 10 times lower than in the infants breast-fed for 6-7 mo. In the latter, a distinct accumulation was found for the tetra- to hexachlorinated congeners compared with maternal concentrations. We conclude that accumulation of PCDDs and PCDFs in infants is as high as expected on the basis of intake data and assuming complete absorption and negligible elimination during the 1st y of life.

Accumulation of 14C‐labeled 1,3,6,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) and octachlorodibenzo‐p‐dioxin (OCDD) from water by rainbow trout fry (Salmo gairdneri) and fathead minnows (Pimephales promelas) was studied using a 5‐d uptake and 24 to 48‐d depuration period. Average exposure concentrations ranged from 4 to 211 ng/L for 1,3,6,8‐TCDD and from 9 to 415 ng/L for OCDD. Equilibrium bioconcentration factors for total 14C in fish, calculated by use of a two‐compartment first‐order rate model, were 2,100 and 5,702 for 1,3,6,8‐TCDD in trout fry and minnows, respectively, and 85 and 2,226 for OCDD in the same species. Elimination rates of both isomers were rapid, with half‐lives of 14C ranging from 6 to 9 d for 1,3,6,8‐TCDD and from 5 to 13 d for OCDD. The highest concentrations of radiolabeled 1,3,6,8‐TCDD and OCDD were found in bile. A metabolite of 1,3,6,8‐TCDD in bile was identified as a conjugate of a hydroxylated tetrachloro‐derivative. Dietary exposure of rainbow trout resulted in low accumulation factors, ranging from 0.034 for OCDD to 0.018 for 1,3,6,8‐TCDD, based on toluene‐extractable radioactivity.

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Study objective -The study aimed to assess through a sentinel practice network the validity ofdata on levels of organochlorine residues in human milk along with personal, lifestyle, and exposure variables of breastfeeding women; to compare the results of this new approach with those of the Lower Saxony breast milk surveillance programme; and to test hypotheses on potential determinants of contamination levels. Design -Eligible women were enrolled into this cross sectional study by a network of 51 paediatric practices when bringing their babies for a U3 infant screening examination (4th to 6th week after delivery).Lifestyle and exposure factors were obtained by questionnaire. All milk samples were analysed for hexachlorocyclohexane, hexachlorbenzole, DDT, dieldrin, polychlorinated biphenyls (PCB) and heptachlor; half the samples were also analysed for dioxin. Analytic statistics were computed using polychotomous logistic regression (PLR).

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