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Dioxin exposure in breast milk and infant neurodevelopment in Vietnam
  1. Pham The Tai1,2,
  2. Muneko Nishijo1,
  3. Nguyen Thi Nguyet Anh1,
  4. Shoko Maruzeni1,
  5. Hideaki Nakagawa1,
  6. Hoang Van Luong2,
  7. Tran Hai Anh2,
  8. Ryumon Honda3,
  9. Teruhiko Kido4,
  10. Hisao Nishijo5
  1. 1Department of Public Health, Kanazawa Medical University, Uchinada, Ishikawa, Japan
  2. 2Biomedical and Pharmaceutical Research Center, Vietnam Military Medical University, Ha Noi, Vietnam
  3. 3School of Nursing, Kanazawa Medical University, Uchinada, Ishikawa, Japan
  4. 4Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan
  5. 5System Emotional Science, Graduate School of Medicine, University of Toyama, Sugitani, Toyama, Japan
  1. Correspondence to Dr Muneko Nishijo, Department of Public Health, Kanazawa Medical University, 1-1, Daigaku, Uchinada, Ishikawa 920-0293, Japan; ni-koei{at}kanazawa-med.ac.jp

Abstract

Objectives Dioxin levels in the breast milk of mothers residing near hot spots of dioxin contamination areas in South Vietnam remain much higher than in unsprayed areas, suggesting that fetuses and breast-fed infants may be exposed to high levels of dioxins. The present study investigated the association of infant neurodevelopment in early infancy and dioxin exposure during the perinatal period.

Methods The study involved 216 mother-infant pairs living near the Da Nang airbase, a dioxin contaminated area in Vietnam. Mothers and infants were followed from birth until infants were 4 months old. Dioxin levels in breast milk were measured to estimate the perinatal dioxin exposure, including the infant daily dioxin intake (DDI) via breastfeeding. Infant neurodevelopmental parameters, including cognitive, language and motor domains were assessed at approximately 4 months using the Bayley Scales of Infant and Toddler Development, third edition (Bayley-III).

Results The level of 2,3,7,8-tetrachlorodibenzo-p-dioxin and polychlorinated dibenzo-p-dioxins/furans-toxic equivalents in breast milk and the infant DDI showed significant inverse correlations with neurodevelopmental scores. When the subjects were divided into four groups according to dioxin levels in breast milk, the moderate and high DDI groups had significantly lower cognitive, composite motor and fine motor scores, and the high polychlorinated dibenzo-p-dioxins/furans-toxic equivalents group had significantly lower fine motor score than the low exposure group. For all domains, neurodevelopmental scores were decreased with increase in the level of 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Conclusion The present study demonstrates a considerable impact of perinatal dioxin exposure on neurodevelopment in 4-month-old infants living in contaminated areas in Vietnam.

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