Maternal blood lead level during pregnancy in South Central Los Angeles

Twenty-five years of public health efforts produced a striking reduction in lead exposure; the blood lead average in the United States has decreased t o less than 20% of levels measured in the 1970s. However, poor minority gro ups that live in large urban centers are still at high risk for elevated le ad levels. In this study, our data showed that pregnant immigrants (n = 1 4 28) who live in South Central Los Angeles-one of the most economically depr essed regions of California-have significantly higher (p <.0001) blood lead levels (geometric mean = 2.3 mu g/dl [0.11 mu mol/l]) than 504 pregnant no nimmigrants (geometric mean = 1.9 mu g/dl [0.09 mu mol/l]). The most import ant factors associated with lower blood lead levels in both groups were you nger age; more-recent date of blood sampling (i.e., decreasing secular tren d); and blood sampling in mid-autumn, instead of mid-spring (i.e., seasonal trend). Blood lead levels of immigrants were strongly dependent on time el apsed since immigration to the United States; each natural log increase in years of residence was associated with an approximately 19% decrease in blo od lead levels. Although blood lead means for both groups were almost the s ame as the estimated national average, 25 of the 30 cases of elevated blood lead (i.e., greater than or equal to 10 mu g/dl [0.48 mu mol/l]) occurred in the immigrant group. The odds ratio (95% confidence intervals within par entheses) for having elevated blood lead levels (a) was 9.3 (1.9, 45.8) if the immigrant engaged in pica; (b) was 3.8 (1.4, 10.5) if the immigrant had low dietary calcium intake during pregnancy; and (c) was .65 (.43, .98) fo r every natural log unit increase of years of residence in the United State s. The control of pica and dietary calcium intake may offer a means of redu cing lead exposure in immigrants.