(Reuters Health) – Kids exposed to high levels of lead decades ago may now be approaching middle age with lower IQs and earning potential than they would have had otherwise, a new study suggests.
These days, doctors warn parents that there’s no safe level of lead exposure. This toxin can damage the developing nervous system in young children, and blood lead levels as low as 5 micrograms per deciliter may lower intelligence quotient (IQ), according to the World Health Organization.
Participants in the current study had average blood lead levels more than twice that high when they were 11 years old in the early 1980s: 10.99 micrograms/dl.
Every 5 microgram/dl increase in blood lead levels early in life was associated with a 1.61-point lower IQ by the time these children reached age 38, as well as reductions in perceptual reasoning and working memory, researchers report in JAMA.
“This suggests at the very least that individuals don’t fully recover from lead-related cognitive injuries received in childhood,” said lead study author Aaron Reuben of Duke University in Durham, North Carolina.
“It also suggests that lead exerts a downward pull on an individual’s cognitive abilities over time regardless of where they start out in life,” Reuben said by email.
For the study, researchers examined data on cognitive function, IQ and socioeconomic status for 565 adults in Dunedin, New Zealand when they were 38 years old, as well as results from blood tests for lead done in childhood.
Childhood blood lead levels ranged from 4 to 31 micrograms/dl.
There were no meaningful differences in lead exposure based on socioeconomic status, and elevated blood lead levels were found in children from poor and affluent families alike.
Participants with childhood blood lead levels above 10 micrograms/dl had average adult IQ test scores 4.25 points lower than their peers with lower blood lead levels.