A new study from George Wehby, professor and head of the Department of Health Management and Policy at the University of Iowa College of Public Health, has found that low levels of lead exposure in early childhood—below the current CDC recommended intervention threshold of 3.5 micrograms per deciliter (μg/dL)—are associated with reduced academic achievement during childhood and adolescence.

Published in JAMA Network Open, the cohort study analyzed data from over 305,000 children born in Iowa between 1989 and 2010. Researchers linked early childhood blood lead test results to standardized math and reading scores collected from grades 2 through 11. The findings revealed that for each 1-unit increase in blood lead levels below 3.5 μg/dL, math scores dropped by 0.47 points and reading scores by 0.38 points on national percentile rankings—declines overall comparable to those seen with a 1-unit increase in blood levels above the 3.5 μg/dL threshold.

“This study provides further evidence on the importance of continuing public health policy efforts to reduce and eliminate lead exposure,” says Wehby. “Reconsidering the current threshold for additional management and interventions might be needed given that an increase in lead levels below this threshold is associated with declines in academic achievement.”

The study’s large sample size enabled Wehby to assess variations in low lead levels. “The study sample and scale allowed for evaluating variation in low lead levels below the threshold currently recommended for additional interventions,” Wehby added.

The findings provide further evidence that there are no safe lead levels and that even low-level lead exposure may have lasting academic consequences. “Encouraging lead testing early in life and continuing to raise awareness of parents about lead harms—including at relatively low levels—can help in identifying children at risk and understanding sources of exposure,” Wehby says. “Continuing to enforce policies aimed at reducing lead exposure at homes and childcare centers and through water would also be important.”