Infant exposure to chemicals in breast milk in the United States: What we need to learn from a breast milk monitoring program

The presence of environmental chemicals in breast milk has gained increased attention from regulatory agencies and groups advocating women's and child ren's health. As the published literature on chemicals in breast milk has g rown, there remains a paucity of data on parameters related to infant expos ure via breast-feeding, particularly those with a time-dependent nature. Th is information is necessary for performing exposure assessments without hea vy reliance on default assumptions. Although most experts agree that, excep t in unusual situations, breast-feeding is the preferred nutrition, a bette r understanding of an infant's level of exposure to environmental chemicals is essential, particularly in the United States where information is spars e. In this paper, we review extant data on two parameters needed to conduct realistic exposure assessments for breast-fed infants: a) levels of chemic als in human milk in the United States land trends for dioxins/furans); and b) elimination kinetics (depuration) of chemicals from the mother during b reastfeeding. The limitations of the existing data restrict our ability to predict infant body burdens of these chemicals from breast-feeding. Althoug h the data indicate a decrease in breast milk dioxin toxic equivalents over time for several countries, the results for the United States are ambiguou s. Whereas available information supports the inclusion of depuration when estimating exposures from breast-feeding the data do not support selection of a specific rate of depuration. A program of breast milk monitoring would serve to provide the information needed to assess infant exposures during breast-feeding and develop scientifically sound information on benefit s an d risks of breast-feeding in the United States.