Breast Milk Lead and Cadmium Levels in Suburban Areas of Nanjing, China

Objective To evaluate levels of lead （Pb） and cadmium （Cd） in the breast milk in the second post- partum month, to investigate the relationship between Pb/Cd levels in breast milk and some sociodemo- graphic parameters, and to explore whether these levels affect the infants＇ physical status or the mothers＇ psychological status （postpartum depression）. Methods A cross-sectional study was conducted between November 2009 and December 2010. Al- together 170 healthy mothers were enrolled from Nanjing Maternity and Child Health Care Hospital. The inclusion criteria were： voluntary to participate in this study, healthy, with no chronic disease, breastfeeding in the second postpartum month, living in a suburban but not non-industrial area of Nanjing, and not occupa- tionally exposed to toxic metals. All the mothers completed a questionnaire and were evaluated based on the Edinburgh Postpartum Depression Scale （EPDS） to identify the risk of postpartum depression. Pb and Cd levels in breast milk were determined by inductively coupled plasma mass spectroscopy. The infants of these mothers were examined for their z scores of weight for age, length for age, head circumference for age, and body mass index for age. Results The median breast milk levels of Pb and Cd were 40.6 μg/L and 0.67 μg/L, respectively. In 164 （96.5%） of the 170 samples, Pb levels were higher than the limit reported by the World Health Or- ganization （〉 5 μg/L）. Breast milk Cd level was 〉 1 μg/L in 54 （31.8%） mothers. The mothers with a his-tory of anemia had a higher breast milk Pb level than those without a history of anemia （41.1 μg/L vs. 37.9 μg/L, P = 0.050）. The median breast milk Cd level in those who were active and passive smokers dur- ing pregnancy was significantly higher than that in non-smokers （0.88 μg/L vs. 0.00μg/L, P = 0.025）. The breast milk Cd level in the mothers not taking iron and vitamin supplements for 2 months postpartum was higher than in those taking the supplements （iron supplement： 0.74μg/L vs. 0.00 μg/L, P = 0.025; vitamin supplement： 0.78 μg/L vs. 0.00μg/L, P = 0.005）. Breast milk Cd level at the second postpartum month was negatively correlated with the z scores of head circumference （r = - 0.248, P = 0.042） and weight for age at birth （r = - 0.241, P = 0.024） in girls. No correlation was found between the breast milk Pb/Cd levels and the EPDS scores. Conclusion Considering the high levels of Pb and Cd in breast milk in this study, breast milk moni- toring programs ar