Lead Levels in the Breast Milk of Nursing Andean Mothers Living in a Lead-Contaminated Environment

Abstract

Concentrations of lead (Pb) in breast milk (PbM) and blood (PbB) were measured in a current cohort of lactating mothers living in Andean communities where women of childbearing age engage in the occupational use of Pb, and compared to results obtained in earlier studies. Mean PbM concentration in the current group of breastfeeding mothers tested in 2012/2013 was 3.73 μg/L (SD: 7.3; range: 0.049–28.04), and significantly lower than the 9.83 μg/L (SD: 12.75; range: 0.2–49) previously observed in breastfeeding mothers in the study area from 1999 to 2007. Breastfeeding women in the current cohort showed an average PbM/PbB ratio of 3.6%, which is in agreement with other studies. The mean PbB level obtained for the current cohort was 7.8 μg/dl (SD: 5.2; range: 1.4–21), and significantly lower than the mean PbB level of 20.8 μg/dl (SD: 16.4; range: 4–73) obtained for the comparison group of breastfeeding mothers tested between 1999 and 2007. A correlation of .687 between paired PbM and maternal PbB was found, indicating that maternal PbB level is a significant predictor of PbM. Current PbM levels remain higher than international averages, but indicate that maternal Pb exposure has declined over time in the environmentally Pb-contaminated study area. The current reduction in Pb in milk and blood of breastfeeding mothers may be due to adherence to a Pb-exposure education and prevention program initiated by the authors in the study area years earlier, as well as recent improvements in local health care delivery.

ACKNOWLEDGEMENTS

The authors thank Universidad San Francisco de Quito Colegio Ciencias de la Salud, Escuela de Medicina, in Quito, Ecuador, for continued support of the Ecuadorian Lead and Mercury Exposure Project. We thank Dr. Gonzalo Mantilla, Dean of Colegio Ciencias de la Salud, Escuela de Medicina, Universidad San Francisco de Quito, for ongoing support and advice. We thank nurse Gladys Pacheco of the Subcentro de Salud, La Victoria, Ecuador, for assistance. We also thank Rosa Mercedes Cruz, auxilliary nurse, and Fabiola Herrera, Erika Herrera, and Jenny Bonifaz, health care providers at La Victoria Subcentro de Salud. We are grateful to Anthony B. Jacobs for excellent technical assistance. The authors thank the David Rockefeller Center for Latin American Studies at Harvard University for support of this project. We are thankful for the support of Dr. Jeremy Bloxham, Dean of Science at Harvard University; Boston Children’s Hospital, Department of Laboratory Medicine; John Butz and associates at Mayo Medical Laboratories in Rochester MN; Harvard Biological Laboratories/MCB; Harvard University Health Services; and the Eunice Kennedy Shriver Center/University of Massachusetts Medical School.

FUNDING

LHB is supported in part by National Institutes of Health (NIH) grant P30 HD04147.