Medical professionals have long known that lead exposure is dangerous for one’s health—but according to a new study, this exposure could have lifelong costs.
Researchers analyzed more than 500 children who had been exposed to leaded gasoline in their youth. The study revealed that children who had been exposed to lead scored several points lower on IQ tests and had a lower socioeconomic status than those who had not been affected or had less exposure.
“What we found was that higher levels of lead exposure in childhood were associated with lower cognitive abilities at age 38," said Aaron Reuben, a psychology graduate student. "And this sort of lower cognitive ability was accompanied by lower socioeconomic status."
The study examined a group of children born during the early 1970s in Dunedin, New Zealand. Vehicles in New Zealand at the time still used leaded gasoline, making the location an optimal site to study childhood lead exposure. Blood samples were collected from 565 participants when they were 11 years old.
“We knew that lead exposure is detrimental to development, but what we didn’t know is to what extent those detriments have lifelong consequences or if there’s sort of a recovery effect,” Reuben said.
Reuben clarified that not only did lead-exposed children's IQ scores fall behind those of their peers, but some of the participants’ IQ scores were also lower in adulthood. Additionally, many affected children had lower salaries compared to those of their parents.
Terrie Moffitt, Nannerl O. Keohane University professor in the Center for Cognitive Neuroscience, noted that even minor differences in IQ can vastly change salaries.
“Among baby-boomer Americans who have about-average mental abilities, an IQ difference of 100 versus 105, which is similar to the 4.25-point deficit in individuals who had elevated lead levels, were compared on net worth near their age of retirement,” she wrote in an email. “Net worth was about $60,000 for adults with IQ of 100, and net worth was about $80,000 for adults with IQ of 105.”
Reuben noted that prior lead exposure studies had difficulty separating the effects of lead from other debilitating circumstances such as poverty. Additionally, few prior studies had attempted to conduct a life-long study given the logistical challenges of following study participants.
He added that the study is useful for analyzing lead exposure in the United States, although the situation in the U.S. is different from that in New Zealand. The New Zealand group had long-term consistent exposure to leaded gasoline, he said, while children in the U.S. have less frequent lead interactions.
“We feel that our findings are going to be relevant for lead-exposed people anywhere, but they’re not going to necessarily tell us what the consequences of very low exposure are,” Reuben said.
However, he expressed hope that the information could be extended to help those in the developing world who encounter leaded gasoline on a daily basis.
Clinicians who are treating lead-exposed children could also benefit from this investigation, Reuben explained. He said he hopes that this study will alert policymakers to the severity of lead exposure and emphasized that lawmakers must examine long-term solutions to the problem.
“Our findings suggest that people don’t recover," he said. "You can detect cognitive impairment associated with childhood lead exposure years later."
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