Temporal trends in the lead concentrations of umbilical cord blood.

Umbilical cord blood specimens from 11,837 births between April 1979 and April 1981 have been analyzed for lead by anodic stripping voltammetry. The mean was 6.56 +/- 3.19 (standard deviation) micrograms per deciliter of blood, and the range was 0.0 to 37.0 micrograms per deciliter. The mean decreased annually by 0.77 +/- 0.03 microgram per deciliter, about 11 percent. Lead concentrations were higher in infants born in summer than in infants born in winter (7.17 versus 5.99, probability less than .001). A Fourier model of the data is presented, and possible reasons for the decline are discussed.