Exposure to lead before birth is associated with lower performance 60 years later on tests of thinking and memory skills in female participants, according to a study published in Neurology. The study does not prove that lead exposure is the cause of the lower scores on tests of thinking and memory skills; it only shows an association.
“Lead exposure in the United States peaked during the 1960s, ’70s and ’80s, and children born during those years are now entering midlife and older adulthood, when these early-life exposures could have long-term effects on their cognitive health,” said study author Ruby C. Hickman, Ph.D., who conducted the research while at Harvard T.H. Chan School of Public Health in Boston, Massachusetts.
Researchers tested lead levels in an unusual way. For a study of radiation exposure, parents in the St. Louis, Missouri, area donated their children’s baby teeth from 1958 to 1972. The study team at Harvard Chan School worked to track down these children six decades later and asked them to take cognitive tests on their home computers or devices.
Researchers still had the baby teeth and tested them for lead levels. Because teeth pick up lead as they are forming, baby teeth can show what levels of lead someone was exposed to before they were born and in early life.
A total of 715 people with an average age of 62 were located, took the tests and had their baby teeth analyzed for lead.
Participants had a median tooth lead concentration of 1.34 parts per million.
For female participants, each one part per million higher concentration of lead during the second trimester was associated with test scores that were lower by 0.16 of a standard deviation, which was the equivalent of three years of aging in their data.
These results took into account other factors that could affect test scores, such as parents’ education level and their family’s financial status.
“While lead exposure has declined over recent decades, the Flint water crisis and recent lead contamination in cinnamon applesauce marketed to young children are examples of ongoing exposure problems in the United States, and lead exposure remains an issue globally as well,” Hickman said.
A limitation of the study is that the participants were mainly white people with high levels of education and higher socioeconomic level as children, so the results may not apply to other groups.
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