Racial difference in lead (Pb) varies as a function of manganese (Mn) level. Mn tertiles as follows: 2nd trimester: <1.25, 1.25–2.26, >2.26; 3rd trimester: <0.70, 0.70–1.28, >1.28; postnatal: <0.27, 0.27–0.56, >0.56; childhood: <0.002, 0.002–0.03, >0.003. Models are adjusted for batch, tooth type, and attrition. Raw data are in metal-to-calcium ratio.