A 1-unit increase in lead levels is associated with worse academic performance throughout school grades, according to a study published online May 28 in JAMA Network Open.

George L. Wehby, M.P.H., Ph.D., from the University of Iowa in Iowa City, examined the association of a 1-unit change in early childhood blood lead levels below 3.5 µg/dL versus ≥3.5 µg/dL with academic achievement in a cohort study that linked birth certificates of children born from 1989 to 2010 with their math and reading test scores for grades 2 through 11 and to their early childhood blood lead testing data.

Up to 305,256 children and 1,782,873 child-grade observations were included in the analytical sample. Wehby found that at a mean childhood age at lead testing of 1.9 years, 37.7% of children had lead values below 3.5 µg/dL. A 1-unit increase in lead levels below 3.5 µg/dL was associated with lower national percentile rank (NPR) scores in math and reading (by −0.47 and −0.38, respectively).

For lead levels ≥3.5 µg/dL, a 1-unit increase was also associated with lower NPR scores in math and in reading (−0.52 and −0.56, respectively). Across grades 2 through 11, the declines in these scores were persistent.

“Reconsidering and potentially lowering current blood lead reference values for intervention may be needed to better address the associations of low-level lead exposures with cognitive and academic outcomes,” Wehby writes.

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