THE INTERACTION OF IRON DEFICIENCY AND LEAD POISONING IN NORMAL CHILDREN. AN EPIDMIOLGICAL STUDY

Abstract

In children the levels of erythrocyte porphyrins (EP) increase exponentially with the blood lead (BPb) above a threshold of 18 μg/dl (P.N.A.S. 79: 3335, 1982). The EP levels are also elevated by iron deficiency. This study was directed to assess the response of normal and Fe deficient children to low levels of Pb. In addition to BPb and EP, serum ferritin (SF) and mean corpuscular volume (MCV) were measured in 3459 children age 1 to 6 years. The normal range for SF and MCV were first established for each year of age. Children with SF < 2 σ below the mean or both SF and MCV < 1 σ below the mean were considered certainly Fe deficient; those with both SF and MCV > 1 σ below the mean were considered certainly Fe sufficient. Children who did not fulfill any of these criteria were left unclassified and excluded from the analysis. The threshold BPb for EP elevation was established by the segmented line technique. The threshold BPb for the entire group of 3459 children was 18 μg/dl; for the 331 Fe deficient children it was 12.5 μg/dl and for the 2314 Fe sufficient children it was 20.3 μg/dl; all slopes of elevation were parallel. Because of the lower threshold BPb, Fe deficient children have a greater increase in EP in response to Pb than Fe sufficient children. These findings demonstrate the greater sensitivity of Fe deficient children to the effect of Pb, probably mediated by the competitive inhibition between Pb and Fe at the ferrochelatase step (Blood 66: 47a, 1985). Fe deficiency increases the sensitivity of children to Pb; Fe supplementation may protect them from the adverse effects of Pb on heme synthesis.

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