Poisoning’s lifelong toll includes lowering social mobility, research shows

Cynthia Brownfield was lucky. When her daughter, then 2 years old, tested for high levels of lead in her blood, she could do something.

Brownfield, a pediatrician in St. Joseph, Miss., got her home inspected and found lead in the windows. She replaced them and had her pipes fixed, too. Her daughter, now 12, was probably affected, says Brownfield. But quick action minimized the exposure. Her daughter is now a healthy, fully functioning preteen.

“We were in the financial position where we could hire a plumber and change the windows,” she said. But others—even her own patients—may not be so fortunate. This reality may have implications even more far-reaching than generally accepted. Findings published Tuesday in JAMA break new ground by suggesting the effects of childhood lead exposure continue to play out until adulthood, not only harming an individual’s lifelong cognitive development, but also potentially limiting socioeconomic advancement. Specifically, Duke University researchers tracked a generation of kids based on data collected through a nearly 30-year, New Zealandbased investigation known as the Dunedin Multidisciplinary Health and Development Study.

They studied the development of more than 1,000 New Zealanders born between April 1972 and March 1973. Because at that time gasoline still contained lead, exposure was common, creating a sizable sample that included people across class and gender. More than half in that data set had been tested for lead-exposure at age 11, and the study tracked brain development and socioeconomic status over the years—making for “a natural time” to use them to study lead’s health effects, said Aaron Reuben, a Ph.D. candidate in neuropsychology at Duke University and the study’s first author.

By the time study participants reached age 38, a pattern emerged: Children who were exposed to lead early in life had worse cognitive abilities, based on how their exposure level. The difference was statistically significant. They were also more likely to be worse off, socioeconomically, than those who had not been exposed to lead. The study found that no matter what the child’s

IQ, the mother’s IQ, or the family’s social status, lead poisoning resulted in downward social mobility.

That was largely thanks to cognitive decline, according to the research.

“Regardless of where you start out in life, exposure to lead in childhood exerts a downward pull to your trajectory,” Reuben said.

Though this research was set in New Zealand, it offers insight into a problem experts said is fairly ubiquitous in the United States and across the globe. The CDC estimates that as many as half a million children between ages 1 and 5 had blood lead levels high enough to cause concern: 5 micrograms per deciliter and up. At least 4 million households across the country have children experiencing significant lead exposure.

“If you want to talk about ‘breaking out of poverty,’ kids who have lead exposure are probably going to have more difficulties,” said Jerome Paulson, an emeritus professor and pediatrician at George Washington University.