Redefine low lead levels: Even one unit increase in Low Lead Levels tied to Poorer Academic Performance in Children: JAMA
A recent study found that a 1-unit increase in blood lead levels-within the range currently considered low (<3.5 microgram/dL) is associated with consistently lower academic performance across school grades. This study was published in JAMA Network Open by George L. and colleagues. This large cohort study from Iowa, reveals that blood lead level increases below the Centers for Disease Control and Prevention (CDC) intervention level are associated with measurable decreases in math and reading scores. These findings imply that the current level is too high to serve as a threshold that protects children's cognitive development and learning outcomes.
In 2021, the CDC reduced the reference value for blood lead level in children to 3.5 μg/dL or greater, marking the level at which public health action is indicated. But researchers have raised questions about whether even lower levels of lead in the blood might be harmful. This research, undertaken between May 2024 and March 2025, aimed to redress this issue by assessing the academic achievement of children with lead levels below and at or above this cut-off.
With a cohort design, the research associated the birth certificates of 305,256 Iowa children born during 1989 through 2010 with their grades 2 through 11 standardized reading and mathematics test scores and with early childhood blood lead tests. The primary outcome assessed was the National Percentile Rank (NPR) reading and math scores.
Children's data were joined within 1,782,873 child-grade observations, offering a large sample to analyze. Of the children investigated:
• 51.0% were boys
• 41.1% were first-born
• 43.9% were born to mothers with a high school education or lower
• The average age at blood lead testing was 1.9 years (SD: 1.5), and 37.7% of children had blood lead levels below 3.5 μg/dL.
The study employed regression modeling to control for sociodemographic, child and maternal health, and school variables in analyzing the relationship between blood lead levels and academic performance.
Key Findings
The analysis demonstrated that even minor increases in blood lead levels—below the 3.5 μg/dL intervention level—were linked to diminished academic performance:
In children with blood lead levels less than 3.5 μg/dL, a 1-unit increase was linked with:
• −0.47 NPR points in mathematics (95% CI: −0.65 to −0.30)
• −0.38 NPR points in reading (95% CI: −0.56 to −0.20)
In children with blood lead levels ≥3.5 μg/dL, with each 1-unit increase, there was associated:
• −0.52 NPR points in mathematics (95% CI: −0.58 to −0.47)
• −0.56 NPR points in reading (95% CI: −0.62 to −0.51)
Notably, these decreases were consistent through grades 2 to 11, reflecting long-term impacts on cognitive and academic achievement independent of the timing of exposure during early childhood.
These findings suggest a need for reconsidering existing thresholds of intervention and increasing public health measures to prevent lead exposure in all settings in which children reside, learn, and play.
Reference:
Wehby GL. Early-Life Low Lead Levels and Academic Achievement in Childhood and Adolescence. JAMA Netw Open. 2025;8(5):e2512796. doi:10.1001/jamanetworkopen.2025.12796
