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We found inverse relations between IQ at the age of seven years and both antenatal and postnatal blood lead concentrations.After adjustment by multiple regression for sex,parents'level of education,maternal age at delivery,parents'smoking status,socioeconomic status,quality of the home environment,maternal IQ,birth weight,birth order,feeding method(breast, bottle,or both),duration of breast-feeding,and whether the child's natural parents were living together,the relation with lead exposure was still evident for postnatal blood samples,particularly within the age range of 15 months to 4 years.For an increase in blood lead concentration from 10 ug per deciliter(0.48 umol per liter)to 30 ug per deciliter(1.45 umol per liter),expressed as the average of the concentrations at 15 months and 2, 3,and 4 years,the estimated reduction in the IQ of the children was in the range of 4.4 points(95 percent confidence interval,2.2 to 6.6)to 5.3 points(95 percent confidence interval,2.8 to 7.8).This reduction represents an approximate deficit in IQ of 4 to 5 percent.Low-level exposure to lead during early childhood is inversely associated with neuropsychological development through the first seven years of life. |
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