Comparison of the rates of exchange of lead in the blood of newly born infants and their mothers with lead from their current environment

Newly born infants (n = 15) were monitored for 6 months after birth or for longer periods to evaluate the changes in isotopic composition and lead con centration in infants as compared with that in women from the same populati on groups and to determine the clearance rates of lead from blood in the in fants. These data represent the first published results for serial blood sa mpling in a relatively large cohort of newly born infants. Blood lead conce ntrations decrease from the cord to samples taken at 60 to 90 days and then increase by amounts varying from negligible to 166%. In spite of concern a bout individual susceptibility to lead pharmacokinetics, changes in isotopi c ratio followed a smooth decrease over time for 9 of the 11 infants born t o migrant parents, and the patterns of variation were quite reproducible. D ata for 2 of 4 infants born to multigenerational Australian parents exhibit ed little change in isotopic ratio over time, and in the other two cases, t he changes were attributed to diet. The rate of exchange (t(1/2)) for the m igrant infants of lead in blood derived from the mother during pregnancy an d the lead from the current environment was calculated by using a linear fu nction and ranged from 65 to 131 (91 +/- 19, mean +/- SD) days. The half-li ves for the exchange of skeletal and environmental lead for 7 of the 8 wome n before significant mobilization of lead from the maternal skeleton ranged from 50 to 66 (59 +/- 6) days. One explanation for the longer half lives f or infants as compared with the mothers may be the proportionally higher co ntribution of current environmental (Australian) lead in the infants at par turition. Exchanges of lead in infants are more complex than for the adults , reflecting inputs from sources such as maternal skeletal lead during brea st feeding.