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Since 1990, blood lead concentrations have been considered to be elevated at 10 µg/dL, based on data on cognitive and behavioral development. Two recent articles address the effects of lead levels below this presumably safe threshold.
In a study involving 172 children, researchers measured blood lead levels from age 6 months to 5 years and IQ at ages 3 and 5 years (complete data were obtained for 87% of participants). Children with low birth weight for age, prematurity, speech defects, and prenatal risk factors for low IQ were excluded. Analyses controlled for multiple variables (e.g., maternal IQ, socioeconomic status, and tobacco use during pregnancy). Higher lifetime average lead levels were significantly associated with lower IQ (4.6-poi…