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Dioxin Exposure and Shortened Duration of Lactation in Seveso

Warner, M*; Eskenazi, B*; Samuels, S; Needham, L; Patterson, D; Mocarelli, P§

doi: 10.1097/01.ede.0000276627.87007.b3

*University of California, Berkeley, United States; †State University of New York at Albany, United States; ‡Centers for Disease Control and Prevention, Atlanta, Georgia; and §University of Milano-Bicocca, School of Medicine, Italy.


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2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a widespread environmental contaminant, has been shown to disrupt multiple endocrine systems in animals. Impaired mammary gland development, leading to impaired lactation has been reported in TCDD-treated mice. Higher maternal levels of other endocrine disrupting compounds have been associated with shortened duration of lactation. No epidemiologic studies have examined the potential effects of TCDD exposure on lactation. On July 10, 1976, as a result of a chemical explosion, residents of Seveso, Italy, experienced the highest levels of TCDD in a human population. Twenty years later, we initiated the Seveso Women's Health Study (SWHS), a retrospective cohort study of the reproductive health of the women. We examined the relationship of TCDD with initiation and duration of lactation for the first postexplosion pregnancy.

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Material and Methods:

The SWHS cohort comprises 981 women who were aged 0 to 40 years in 1976 and resided in the most contaminated areas. Individual TCDD exposure was measured in archived sera collected soon after the explosion by high-resolution mass spectrometry. For each live birth after the explosion, women were asked whether they breast-fed and, if yes, how many months. Duration of lactation for the first live birth after the explosion was examined as a continuous dependent variable using multiple linear regression.

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In total, 252 (64%) women initiated breast-feeding, and the average duration of lactation was 4.6 (±4.3) months. More highly exposed women were nonsignificantly more likely to initiate breast-feeding (OR per 10-fold increase in TCDD = 1.4, 95% CI: 0.9–2.0). However, duration of lactation (in months) was nonsignificantly decreased for each 10-fold increase in TCDD (β = −0.34, 95% CI: −0.96 to 0.27).

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These results suggest that TCDD exposure, like other endocrine disrupting compounds, may affect women's duration of lactation. Multivariate results will be presented and interpreted in light of study advantages and limitations.

© 2007 Lippincott Williams & Wilkins, Inc.