Absorption and Retention of Lead by Infants

Abstract

Summary: Eighty-nine metabolic balance studies were performed with 12 normal infants ranging in age from 14–746 days. Intake and fecal and urinary excretions of lead were determined and net absorption and net retention were calculated. Subjects were fed milk or formula and commercially prepared strained foods. Intakes of lead ranged from 0.83–22.61 μg/kg/day with a mean of 9.43 μg/kg/day. Urinary excretion averaged 1.02 (SD 0.68) μg/kg/day and was positively correlated with lead intake (Fig. 1). Fecal excretion was highly correlated with intake of lead (Fig. 2); fecal excretion exceeded intake in 10 studies. In 61 balance studies with lead intakes greater than 5 μg/kg/day, net absorption averaged 41.5% of lead intake and net retention averaged 31.7% of intake.

Retention of lead was highly correlated with lead intake (Fig. 3). Urinary plus fecal excretion of lead exceeded intake in 19 of 28 balances in which lead intakes were less than 5 μg/kg/day. Absorption and retention of lead were inversely correlated with intake of calcium (Fig. 4). Absorption and retention of lead accounted for greater percentages of intake of lead in this study of infants and young children than have been reported in studies of older subjects.

Speculation: Highly efficient absorption and retention of ingested lead by young children may be partly responsible for the high prevalence of lead intoxication in this age group.