From Boston, at a meeting of the American Association for the Advancement of Science

Breast development is delayed in teenage girls exposed to the pollutant dioxin in the womb and as infants, finds a long-term Dutch study that tracked mother-baby pairs from birth through puberty.

"Dioxin throws a monkey wrench into a number of cellular processes," says Linda Birnbaum of the U.S. Environmental Protection Agency, whose rat studies support the new results.

Scientists became aware of dioxin's detrimental health effects in the early 1970s. Janna Koppe, a pediatrician at the University of Amsterdam, says she and her colleagues began their study after research showed that people in the Netherlands were exposed to dioxin levels twice as high as in other European countries. In addition to 14 mother-baby pairs originally enrolled in 1987, 120 pairs joined the study in 1990 and 1991.

Dioxin levels, as well as a number of other factors, were measured in each mother's and newborn's blood and in the mother's breast milk at birth. Fat in the body routinely moves from one area to another, says Koppe, making fat-rich breast milk an excellent yardstick for measuring fat-binding contaminants such as dioxin in the body.

Researchers did a number of follow-ups during the children's first year, and again at 30 months, 8 to 12 years, and, most recently, 13 to 18 years.

All 18 girls who consented to follow-ups as teens showed delayed initiation of breast development, perhaps due to dioxin's ability to counter the actions of estrogen, the researchers speculate. This harmful effect was just the latest in a series found over the length of the study. It's known that the chemical binds to the body's aryl hydrocarbon receptor, which is involved in a number of developmental pathways and processes, says Birnbaum.

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