Higher Lead Levels Linked to Decrease in Childhood Academic Performance: Study

Even children with “acceptable” lead levels that are under the current CDC threshold of 3.5 μg/dL, still face measurable declines in academic performance.

A new study indicates that children with elevated blood lead levels score lower on math and reading tests from second grade through their junior year of high school.

Lead is a toxic heavy metal that can cause permanent brain damage or other severe, long-term health consequences, especially among children, who are still developing and often do not show immediate signs or symptoms of lead exposure. 

Even short-term exposure may lead to headaches, abdominal pain, vomiting and anemia. With prolonged exposure, children can experience irritability, fatigue, muscle aches, constipation, difficulty concentrating, tremors and weight loss. In more severe cases, lead poisoning can result in nervous system injury, seizures, developmental delays, and in extreme cases, coma or death.

While the U.S. Centers for Disease Control and Prevention (CDC) lowered the blood lead reference value to 3.5 μg/dL in 2021, as part of an effort to identify and intervene earlier in cases of lead exposure, a new study published in JAMA Network Open suggests that even this threshold may be too high to fully protect children from the cognitive and developmental harms associated with lead.

While previous research has linked lead exposure during childhood to lower test scores, the new study by researchers from the University of Iowa focused on blood lead levels much lower than typically analyzed.

The study, led by Dr. George L. Wehby, looked at 305,000 children and nearly 1.8 million test results. Researchers linked birth records for children born in Iowa between 1989 and 2010 to their math and reading scores from grades 2 through 11, as well as to blood lead test results typically taken around age 2.

The researchers found that, overall, 38% of children tested had blood lead levels below 3.5 μg/dL, the rest had levels above the CDC reference range.

The study found that even small increases in blood lead levels were linked to lower academic performance in math and reading for students from grade 2 through grade 11. The declines were seen both below and above the CDC’s current reference threshold of 3.5 μg/dL.

• For blood lead levels below 3.5 μg/dL:
  • Math scores dropped by 0.47 national percentile points per 1 μg/dL increase
  • Reading scores dropped by 0.38 national percentile points per 1 μg/dL increase
• For blood lead levels above 3.5 μg/dL:
  • Math scores dropped by 0.52 national percentile points per 1 μg/dL increase
  • Reading scores dropped by 0.56 national percentile points per 1 μg/dL increase

Researchers said test scores were much lower in the group with lead levels in the low “safe” range currently designated by the CDC. This range typically does not call for further testing or interventions when detected because it is considered “safe.”

The data indicated the drop in academic scores was consistent across all grade levels.

Researchers concluded the test scores indicate a need to lower current blood lead reference values beyond the CDC mandated levels, to help “better address the association of low-level lead exposures with cognitive and academic outcomes.”

Childhood Lead Exposure Risks

In addition to the current findings, a study published by Duke University in 2020 concluded lead exposure during childhood can change the structural integrity of the brain later in life, which may lead to long lasting side effects, including mental health disorders, attention deficit hyperactivity disorder (ADHD) and others.

While children are commonly exposed to lead through paint in older homes, recently more than 500 cases of lead poisoning were linked to recalled applesauce pouches manufactured by brands like Schnucks, WanaBana and Weis. The majority of the cases of lead poisoning were among children younger than two years old.

Additionally, many baby food products have tested positive for lead, arsenic, mercury and cadmium. The tainted baby food was manufactured by major brands such as Gerber, Beech-Nut, Nurture and others.

The consumption of these products has led to a number of children suffering from neurological conditions, ADHD, autism and other side effects of heavy metal poisoning. As a result of these findings, dozens of toxic baby food lawsuits have been filed against the manufacturers.