Methodology for characterizing distributions of incremental body burdens of 2,3,7,8-TCDD and DDE from breast milk in North American nursing infants

A clear picture of ranges of doses of breast-milk contaminants experienced by nursing infants in North America has not yet been described, resulting in a significant gap in our understanding of potential health risks to infants from there contaminants. While point estimates of incremental dose have appeared in the published literature, these do not account for the wide variability in exposures experienced by nursing infants. This research expands on the current state of understanding of breast-milk contaminant exposure by characterizing distributions, rather than point estimates, of dose. Distributions of milk intake by nursing infants were characterized to examine intake of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and dichlorodiphenyl dichloroethane (DDE). The results indicate that, despite the uncertainties inherent in modeling incremental body burdens of chemicals from nursing, estimating incremental infant body burdens of lipophilic chemicals from breastfeeding using point estimates may result in overly conservative estimates of the contribution of breastfeeding to long-term body burdens of those chemicals in children. To develop reliable estimates of incremental body burden from nursing, depuration via lactation and half-life in the infant should be considered. Further, incremental infant body burdens of lipophilic chemicals increase rapidly at the start of lactation, but decrease after approximately 5 to 6 mo; by 2 yr postpartum, incremental body burdens have decreased substantially. Given the benefits afforded to infants who breastfeed, and because breastfeeding does not necessarily lead to significantly increased long-term body burdens in infants, breastfeeding should be encouraged and promoted.