The continuing hazard of lead exposure and its effects in children

Recent epidemiological data have shown in U.S. children aged six months to five years, that an estimated four percent, or approximately 675,000 children, have increased lead absorption (i.e., blood lead concentration (PbB) greater than or equal to 30 micrograms Pb/dl (microgram%) whole blood). The rate was highest among low income, inner city black children, among whom 18.6% or approximately 159,000 show PbB greater than or equal to 30 micrograms%. There have been substantial reductions in the use of lead in gasoline and in lead in food during the past four years. Although the use of lead in residential paints was banned in the U.S. in 1977, a large stock of lead painted old housing remains in use today. Until this substandard old housing is completely renovated or replaced, it will remain the principle environmental lead hazard for young children. Regarding effects of lead in the CNS, there is agreement on the following: 1) sustained PbB greater than or equal to 60 micrograms% during the early preschool years substantially increases the risk of later learning impairment in school, 2) sustained PbB greater than or equal to 40 micrograms% may increase the risk significantly but moderately, 3) the clinical significance of sustained PbB during early childhood in the range of 25-40 micrograms% remains uncertain, and 4) prospective longitudinal studies are essential to delineate the CNS effects of low level lead exposure. The primary screening test for increased lead absorption is the free erythrocyte protoporphyrin (FEP) micro test. This test will detect 95% or more of children with PbB greater than or equal to 50 micrograms%; however, less than 50% are detected by the FEP test when PbB = 30-50 micrograms%.