Study shows lead exposure alters children’s lives decades later
Children with elevated blood-lead levels at age 11 ended up as adults with lower cognitive function and lowerstatus occupations than their parents, according to research that offers one of the clearest looks yet at the potential long-term health impact of the potent neurotoxin.
The findings, published Tuesday in JAMA, were based on a study that followed about 1,000 children born in the early 1970s in the coastal city of Dunedin, New Zealand. More than half were tested for lead in 1983, and nearly three decades later, those who’d had higher blood-lead levels as children were more likely to have lower IQs and to wind up lower on the socioeconomic ladder. Both associations remained even after researchers accounted for the children’s IQs, their mothers’ IQs and their social-class backgrounds.
“Lead damages brain health. We know what it does,” said study co-author Aaron Reuben, a graduate student in clinical psychology at Duke University. “What we didn’t know until this study was, how long do those effects last? … There’s no reason to believe they ever go away.”
Public health officials have repeatedly said that there is no safe level of lead in a child’s blood and that lead exposure can seriously affect the IQ and attention span of children, as well as cause other problems. But the new study adds another layer of evidence to what many scientists have long suspected — that environmental exposures to lead not only risk an array of physical, behavioral and cognitive problems but can change the very trajectory of a child’s life.
It also raises questions about how best to respond to catastrophes such as the water crisis in Flint, Mich., in which thousands of young children were exposed for months to lead-tainted water. Although many of those children are eligible for a range of interventions, including nutritional and educational programs, Reuben and his co-authors note that short-lived public responses may not be enough given the potential lifelong effects.
“The thing that surprised me is that the impairment you experience once exposed to lead doesn’t go away,” Reuben said. “Even mild cognitive impairment really seemed to have a knock-on effect to the social trajectories people’s lives took. We know from other studies that even small changes in IQ can have large implications for earnings potential and wealth over time.”
The study has clear limitations. The children growing up in 1970s New Zealand likely experienced ongoing lead exposures during childhood, mainly from emissions in the air. The way that affected them over an extended period could differ from the consequences of relatively short but severe exposures, as happened in Flint.
Researchers also had only a snapshot of lead levels from the tests taken when the children were 11, and there was no way to measure their cumulative lead exposures by the time they were 38, Reuben said. In addition, the conclusions were based on only one group of primarily white children in one city, so generalizing the findings to other populations and settings could be problematic.
Still, the findings were stark enough to prompt David C. Bellinger, a professor of environmental health at Harvard, to write in an accompanying JAMA editorial that much more needs to be done to eliminate lead exposures in every form. That includes more stringent lead-abatement efforts, more rigorous screening, more determined cleanup of the “vast reservoirs of lead that remain” in the environment, in everything from paint to plumbing, he said. Bellinger also argues for finding educational interventions to help improve outcomes for lead-exposed children, in the hope that their futures won’t be defined by the environmental threats of their childhood.
“Until these steps are taken, problems such as those in Flint are almost certain to occur periodically,” Bellinger warns. “Children will continue to experience the greatest harm from lead exposure, and disadvantaged children will bear a disproportionate share of the burden.”