Exposure to lead levels during childhood negatively affects language function and may even cause brain cells to reorganize to compensate, say researchers from Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine in Ohio.
Starting in 1979, researchers enrolled pregnant women living in neighborhoods with high rates of childhood lead poisoning and followed their offspring from birth through early childhood. The kids underwent regular blood tests to determine exposure to lead as well as intelligence, neurological, and behavioral tests. Researchers also tracked each child's academic achievement during the school years.
During young adulthood, 42 of the study participants underwent magnetic resonance image (MRI) testing while answering questions designed to assess verbal ability. Using images from each participant's MRI, researchers determined the relationship between childhood blood lead levels and the parts of the brain activated during language tests.
The results? Young adults who had higher blood lead levels during childhood tended to have less activity in the areas of the brain typically associated with semantic language function (which determines the meanings of words and sentences). The study authors suggest that exposure to lead early in life disrupts normal brain development and permanently affects the brain's ability to learn language.
The MRI results also revealed that young adults who'd been exposed to high levels of lead as kids tended to have more activity in another part of the brain typically not involved in language function. The brain may actually compensate for language learning difficulties caused by lead exposure by engaging other areas of the brain and creating new neural pathways to facilitate learning.
What This Means to You. The results of this study show that language abilities may be permanently affected by exposure to lead in childhood. Lead-based paint is the most common source of childhood lead exposure, and kids who live in older homes are particularly at risk. Symptoms of lead exposure include irritability or behavioral problems, difficulty concentrating, headaches, and loss of appetite, among other symptoms. If you believe your child may have been exposed to lead or has symptoms of lead exposure, talk to your doctor.
Source: Weihong Yuan, PhD; Scott K. Holland, PhD; Kim M. Cecil, PhD; Kim N. Dietrich, PhD; Stephanie D. Wessel, MS; Mekibib Altaye, PhD; Richard W. Hornung, DrPH; M. Douglas Ris, PhD; John C. Egelhoff, DO; Bruce P. Lanphear, MD, MPH; Pediatrics, September 2006.
Reviewed by: Steven Dowshen, MD
Date reviewed: October 2006