Health Effects of Lead Exposure on Children

There is no known level of lead exposure that is considered safe.  The human body cannot tell the difference between lead and calcium, which is a mineral that strengthens the bones. Like calcium, lead remains in the bloodstream and body organs like muscle or brain for a few months. What is not excreted is absorbed into the bones, where it can collect for a lifetime. 

As lead exposure increases, the range and severity of symptoms and effects also increases, even blood lead concentrations as low as 5 µg/dl (micrograms per deciliter, which converts to 50 parts per billion), once thought to be a “safe level”, may result in decreased intelligence in children, behavioral difficulties and learning problems.  Over the past 50 years, a growing body of scientific evidence has documented the connection between elevated childhood blood lead levels (EBLLs) and neurological damage, decreased IQ, increased blood pressure, anemia, gastrointestinal issues, stunted growth, seizures, coma, and—at very high levels— death.  

Recent research has found that even very low levels of lead exposure can have a detrimental impact on a child’s IQ, likelihood of having a learning disability, educational attainment, and reading readiness at kindergarten entry.  Compared to adults, children are at greater risk for two main reasons: First, they are more likely to ingest lead and absorb a higher percentage of ingested lead. Secondly, their rapidly growing minds and bodies are more susceptible to lead’s harmful effects. No safe blood lead level in children has been identified, and there is a direct relationship between childhood blood lead levels (BLLs) and the severity of resulting health and educational problems. 

Tens of millions of U.S. children have been adversely affected by lead exposure in the years since its negative effects were first discovered.  It is also a costly disease, with recent estimates putting its price tag at over $50 billion in a single year due to lost economic productivity resulting from reduced cognitive potential.  Low-level chronic exposure may have an even greater effect on IQ than a single instance of very high BLL.  Considering the costs to the special education system along, one study conservatively estimated that it costs $38,000 over three years to educate a child with lead poisoning. 

Recent studies confirm that the connection between blood lead and poor educational outcomes remains true for BLL as low as 3–4 μg/dL (micrograms per deciliter, 30-40ppb); these recent findings on the relationship between childhood BLL, educational potential, and performance on school tests puts IQ research in perspective.

--A series of North Carolina studies of over 57,000 children found that children with a BLL as low as 4 μg/dL (40 parts per billion (ppb)) at three years of age were significantly more likely to be classified as learning- disabled than children with a BLL of 1 μg/dL (10 ppb). Researchers also found a dose-response relationship between end-of-grade test scores and BLL: BLLs of 3 μg/dL(30 ppb) and above were associated with decreases in test scores.  Furthermore, children with a higher BLL were less likely to place into advanced and intellectually gifted programs. These results held true even when researchers accounted for factors such as race, family income, and other factors that might affect learning-disabled status. These results have been replicated in Connecticut, and researchers observed the same associations between elevated BLL and decreased achievement on reading and math tests.

--In a study of over 48,000 school children in Chicago, BLLs as low as 5 μg/dL (50 ppb) were associated with lower scores on third grade reading and math tests.  Researchers determined BLL had a strong relationship with test scores, similar to factors such as birth weight, maternal education, and race/ethnicity. Non-Hispanic black students in this study had an average BLL more than twice that of non-Hispanic white students.

--A study of 3,400 kindergarten students in Providence, Rhode Island demonstrated that increased BLLs were associated with decreased scores on the Phonological Awareness Literacy Screening for Kindergarten (PALS-K), a standardized assessment of children’s cognitive development and literary skills. Children with BLLs of greater than 10μg/dL (100 ppb) had PALS-K scores that were 13 points lower than children with BLLs less than 2μg/dL (20 ppb). The negative relationship between BLL and reading readiness persisted even after adjustment for demographic factors, primary language, and socio-economic status. Only one in four black children included in one study had a BLL of 3 μg/dL (30 ppb) or less, while almost half of white children had a BLL at or below 3 μg/dL. 

--In the Chicago study of BLL and third grade test scores, non-Hispanic black students had a mean blood lead level of 7.7 μg/dL(70 ppb)—more than twice thatof non-Hispanic white students at 3.7 μg/dL (30 ppb). One of the North Carolina studies found that once BLL was taken into account, race was no longer a predictor of being classified as learning-disabled.

How lead affects childrens' health.