Children with elevated blood-lead levels at age 11 ended up as adults with lower cognitive function and lower-status occupations than their parents, according to research that offers one of the clearest looks yet at the potential long-term health effects 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, mothers’ IQs and social-class backgrounds.

“Lead damages brain health. We know what it does,” said study co-author Aaron ­Reuben, a graduate student 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, Reuben and his co-authors note that short-lived public responses may not be enough given the potential lifelong effects.