International Study Finds Breast Milk Free of Significant Lead Contamination

The recent article by Gulson et al. (1) should provide reassurance to most women that their breast milk is free of significant lead contamination. Their data found that breast milk contained lower levels of lead than infant formula or infant food. Although small amounts of lead may be found in all human tissues, the milk of the vast majority ofwomen does not present a lead hazard to their babies. Unfortunately, the authors formed unwarranted conclusions from their data, and the title of the press release, "International Study Finds Mothers' Lifetime Lead Exposures May Put Breast-fed Newborns at Risk," (2) was misleading. As a result, women reading this press release may decide not to breast-feed, thus depriving their babies of the most healthful food available to them and placing their infants at increased risk for a variety of infectious diseases. This press release is in conflict with the decade-old public health goals to increase both the percentage of mothers who breast-feed and duration of breastfeeding in the United States (3). Why did this happen? What lessons can we learn from the chain of events that led to the release of such misinformation? How can we avoid exposing the public to misinformation that can have dangerous public health consequences? Gulson et al. (1) examined a small, nonrepresentative sample of 15 eastern European women emigrants and their Australian-born babies (n = 16) and compared them with 6 second-generation Australian women and their 8 babies. None of the women were exposed to lead except through background levels in the diet. The study reported no difference in either blood lead or breast milk lead concentrations of European emigrants versus Australian mothers. All had low blood lead values [geometric mean (GM) = 2.02 pg/dl; range 0.91-3.61 pg/dl]. They also had very low levels of lead in their breast milk (GM = 0.7 pg/kg; range 0.09-2.09 pg/kg), lower than lead levels in infant formula (GM = 1.8 pg/kg; range 0.36-4.3 jig/kg) or infant foods (GM = 4.1 jig/kg; range 1.4-27 pg/kg). The authors reported that maternal blood isotope ratios and breast milk lead concentrations predicted infant blood isotope ratios, although the level of statistical significance for this analysis (p = 0.09) was, at best, marginal and the coefficient for infants' blood lead concentration was negative. Gulson et al. (1) also estimated the percentage of each child's blood lead attributable to breast milk (36-80%) and/or infant formula (24-68%). The authors did not estimate the uncertainty surrounding these percentages, they did not provide data on infants' blood lead levels, and they did not compare infants' blood levels related to breast milk and formula. We believe the data of Gulson et al. (1) suggest that compared with other infants, breast-fed infants are not at increased risk from lead poisoning. The authors' analysis of predictors of lead isotopic ratios is not meaningful in establishing risk for lead poisoning. While the isotopic ratio may be useful in establishing the source of lead, it is the mother's body burden of lead and total blood lead level that influence breast milk concentrations of lead and, ultimately, the infant's exposure to lead from breast milk. Gulson et al. (1) speculate on which women are highly exposed to lead and then suggest a public health practice recommendation of screening women for lead body burdens. While it may be useful to recommend screening for highly exposed women, we suspect that only a small fraction of women are highly exposed. Screening recommendations should accurately target exposed women, such as those employed in lead-exposed jobs where blood lead levels are routinely measured and medical removal already occurs (4). In addition, action levels at which breast-feeding is contraindicated must be set before targeted screening could be made meaningful. No action level was provided by Gulson et al. A useful action level must weigh both the risks and benefits from breast milk. The Health Resources and Services Administration (HRSA) has published a blood level action level of 40 pg/dl or above as a contraindication for breast-feeding (5). None of the 2,925 women 15-44 years of age who participated in Phase 2 of the Third National Health and Nutrition Examination Survey had a concentration that high, and only two women had levels even half that high (6). The Health and Human Services Federal Advisory Committee on the Prevention of Childhood Lead Poisoning has not considered a recommendation about screening of women to prevent lead poisoning in children, but it is the appropriate group to do so if such a recommendation were necessary. We became aware of the study by Gulson et al. (1) when the Centers for Diseases Control and Prevention (CDC) received media inquiries about the NIH press release describing the article. We were surprised that the press office would endorse a title that could discourage women from breast-feeding, in spite of well-established public health goals to the contrary. We became alarmed after we examined the article and contrasted the actual data in the report with the authors' conclusions and the press release. Healthy People 2000 set the nation's goal for the proportion of mothers breast-feeding their infants at 75% during the early postpartum period, 50% through 6 months, and 25% through the first year of life (3). Because these goals have not been achieved, they have been directly adopted into Healthy People 2010. Informing the public about important scientific findings is valuable, but it is crucial that the media message be accurate. Just as editors and press officials must verify technical information with technical experts other than the authors, so must they verify health policy guidance with public health experts. As noted in the draft of Healthy People 2010 (7),