Association of erythrocyte protoporphyrin with blood lead level and iron status in the second National Health and Nutrition Examination Survey, 1976-1980.

Both iron status and body burden of lead influence heme biosynthesis. Measurement of protoporphyrin IX in the circulating erythrocyte (EP) has been used to index the extent of lead exposure and iron deficiency. The association of iron status and blood lead level with the level of EP in whole blood for persons ages 6 months through 74 years in the general U.S. population has been investigated by using data obtained in the second National Health and Nutrition Examination Survey (NHANES II). Iron status was defined as a function of percentage transferrin saturation (%TS) and total iron-binding capacity (TIBC). Both low iron status (%TS less than or equal to 16.0 or TIBC greater than or equal to 450 micrograms/dl serum) and elevated blood lead levels (greater than or equal to 30 micrograms/dl) were associated with increased EP concentrations. The analysis of the proportions of persons in the U.S. population with EP levels above the 95th percentile (30 micrograms EP/dl of whole blood in the NHANES II data) support the concern that iron status has considerable influence on interpretation of EP levels recommended for use in screening programs aimed at identifying children with lead toxicity. With screening techniques based on EP only, currently used in various public health programs, a considerable number of children with blood lead levels of greater than or equal to 30 and less than or equal to 50 micrograms/dl are not referred for further diagnostic evaluation.