Studies of blood and breast milk from mothers have demonstrated that dioxins are eliminated from the body during breast feeding. The purpose of this paper is to explore the relationship between dioxin levels in blood and breast feeding for participants in a large population-based exposure study. The focus is on exploring 1) the effects of breast feeding a first child compared to additional children and 2) a time period interaction related to the changing levels of dioxins in the environment over time.

In general, breast feeding before 1959 was significantly associated with a higher TEQ in blood while breast feeding from 1960–1979 and after 1980 were significantly associated with a lower TEQ in blood. This suggests that breast feeding during the historic period when the dioxin content in the food supply was high was not associated with reductions in blood TEQ, whereas breast feeding more recently when the women were eating less contaminated foods was associated with reductions in blood TEQ.