Response

Abstract

We thank Professor Koo for his observations and agree that the questions he raises are important. In our initial article describing lead mobilization during pregnancy, 1 Gulson BL James CW Mahaffey KR Mizon KJ Korsch MJ Vimpani G Pregnancy increases mobilization of lead from maternal skeleton. J Lab Clin Med. 1997; 130: 51-62 Google Scholar we mentioned that most of the subjects had dietary calcium intakes between 400 and 800 mg/d. The 1994 National Institutes of Health Consensus statement on dietary calcium recommended that the daily calcium intake during the last trimester of pregnancy should be about 1100 mg Ca per day and should be increased to about 1200 to 1300 mg Ca per day during lactation. Thus intake above the level we observed in our subjects appears to be necessary for protection, but we have not carried out a precise dose titration. Lead concentration and isotope distribution have been measured in the breast milk of some of the subjects; these findings have just been published in Environmental Health Perspectives. 2 Gulson BL Jameson CW Mahaffey KR Mizon KJ Patison N Law AJL et al. Relationships of lead in breast milk to lead in blood, urine and diet of the infant and mother. Environ Health Perspect. 1998; 106: 667-674 Google Scholar In brief, we found very low concentrations of lead in breast milk (0.7 ± 0.7 μg Pb/kg or parts per billion), but a significant contribution to lead in the breast milk is derived from the maternal skeleton and transferred to the infant. Thus mothers should breast-feed their infants, but if they have been exposed to high concentrations of lead in the past (and hence have a high bone store) or are exposed from current activities such as renovations involving leaded paint or hobbies involving lead, and are concerned that they may transfer the lead to the infant, they should have a blood lead test. No guidelines are available for lead in breast milk, but we recommend that if a mother's blood lead is above 20 μg/dL, she should also have the breast milk analyzed for lead.