Lead Poisoning’s Lifelong Toll Includes Lowering Social Mobility, Researchers Find

Children watch lead removal
Children watch while soil is removed the yards of several homes in the Boyle Heights area where high levels of lead were found due to contamination by the Exide Technologies battery plant Aug. 2014. (Mark Boster/Los Angeles Times via Getty Images)

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 got them replaced 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. In California, health officials are acutely aware of the dangers posed by lead, and state lawmakers are considering a bill that would require all children between six months and six years old to be tested routinely for exposure to the toxic metal.

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 Zealand-based 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 sizeable 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 socio-economic status over the years — making for “a natural time” to use them to study lead’s health effects, said Aaron Reuben, a PhD 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.

Last year’s water crisis in Flint, Mich., brought lead exposure front and center as a public health concern. Meanwhile, a Reuters investigation published this winter found elevated lead levels in almost 3,000 communities around the country. In California, the investigation found that more than 7 percent of children screened in the Fruitvale neighborhood of Oakland had elevated levels of lead in their blood. In Selma, a city located about 15 miles southeast of Fresno, more than 6 percent of children who were tested had high lead levels.

By comparison, about 5 percent of children tested in Flint showed high levels of lead in their blood after the city’s drinking water was found to be contaminated, according to the Reuters report.

In 2012, 650,402 California children under the age of 21 were tested for lead, and about 13,000 of them — 2 percent — had lead levels above the threshold considered potentially unsafe, according to data from the state’s Department of Public Health.

The Centers of Disease Control and Prevention recently changed its guidelines to suggest that any childhood exposure to the chemical is harmful, and is pushing to get rid of lead poisoning in kids by 2020.

In the U.S., children at risk are typically poorer and racial minorities — in part because they more often live in older houses with lead paint. This is a stark difference from the research population, which tended to be white. However, because the study spanned a period of time in which lead was still used in gasoline, the lead exposure measured in the study spanned a wider class spectrum.

That adds greater consequence to these findings, many said.

“Kids who are poor, or who have some of these other social determinants of health that are negative — they end up with a double whammy. Whatever health consequences they have from being poor, those are added to the additional consequences of being exposed to lead,” said Jerome Paulson, an emeritus professor and pediatrician at George Washington University. Paulson has researched lead’s effects on children, although he wasn’t involved with this study.

“If you want to talk about ‘breaking out of poverty,’ kids who have lead exposure are probably going to have more difficulties,” he added.

That said, these conclusions aren’t perfect. For instance, the research doesn’t account any variation in how the children who were tested may have been previously exposed to lead, or how their continued lead exposure through adulthood may have differed. Those who worked in jobs like construction, for instance, may have had greater lead exposure than those in white-collar jobs, Paulson noted. But on the whole, he said, it makes a strong case for the long-term impact of childhood lead exposure.

Pennsylvania, Maryland and Massachusetts, which all have cities with concentrated areas of older housing, have identified lead poisoning as a major child health hazard. The CDC has also embraced “primary prevention” — testing homes for lead and removing it before people move in and risk exposure. But securing resources for lead testing, screening and abatement poses its own set of challenges.

The JAMA study illustrates, in part, one such difficulty. Lead poisoning happens over years, not overnight. So illustrating the impact, even if it’s ultimately significant, is hard to do.

“Prevention doesn’t have a lot of pizzazz. If you prevent something from happening, it’s a wonderful thing, but it’s hard to measure and take credit for,” said David Bellinger, a neurology professor at Harvard Medical School and a professor in the environmental health department of the university’s public health school, who wrote a commentary that ran alongside the JAMA paper.

And funding for such programs is often unreliable, said Donna Cooper, the executive director of Public Citizens for Children and Youth, a Pennsylvania-based nonprofit that advocates on behalf of young people. For instance, the White House’s initial budget plans would boost some lead abatement funds but slash other grants used for similar purposes. And for many states, she said, even what’s long been available isn’t enough to meet the scope of the concern.

“We have very clear CDC guidance on what should be done, and no money to back it up,” Cooper said. “It ebbs and flows with the headlines.”

California Healthline reporter Ana B. Ibarra contributed to this report.

This story was produced by Kaiser Health News, an editorially independent program of the Kaiser Family Foundation.

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