Lead in milk and infant blood: a dose-response model

As part of a longitudinal study of the sources and developmental effects of current urban lead exposure, lead was measured in tap water from the homes of 249 infants, in 100 breast milk samples, and in 73 samples of the infant formula used by non-nursing mothers. Also, the blood lead levels of the infants who received these fluids were determined at birth and at 6 months of age. Among the infants who were breast fed, the lead content of their milks correlated very well with their 6-month blood lead levels (r = .42, P = .0003). The mean lead content of infant formulas and breast milk were not significantly different, nor was the blood lead of children fed one or the other. Lead levels in maternal milk correlated poorly with umbilical cord blood lead (r = .18, P = .10). Tap water and infant blood lead levels correlated minimally (r = .11, P = .10). Since milk represents much of the diet of young infants and because breast milk lead levels are stable, it is possible to relate blood lead and daily dosage in this population.