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Lead exposure has been linked to lower IQ in children and adolescents, but effects later in life have not been studied on a large scale.
Researchers reported on 565 individuals from a 1972–73 New Zealand birth cohort whose blood lead level had been measured at age 11 years. At age 38 years, IQ was reassessed and socioeconomic status scored by job type using a standard national formula (range [low to high], 10 to 90). Adjustments were made for child and maternal IQ, as well as childhood socioeconomic status.
Blood lead levels ranged from 4 to 31 μg/dL, with a mean of 11 μg/dL. Forty-six percent of children had levels >10 μg/dL. After adjusting for potential covariates, every 5-μg/dL increase in blood lead level at age 11 was associated with a …