Study: Being Exposed to Lead as a Child May Alter Personality

Despite regulations put in place to reduce lead exposure, the Centers for Disease Control and Prevention (CDC) estimates that last year 3.6 million U.S. families were at risk of lead poisoning. Now, a new study demonstrates this exposure could potentially negatively affect children's personalities in adulthood.

For the study, researchers collected personality questionnaire results from over 1.5 million people who grew up in various areas—reaching 269 different U.S. counties and 37 European nations. They also reviewed historical data from the Environmental Protection Agency (EPA) on atmospheric lead levels where responders grew up, adjusting for age and socioeconomic status.

They found that those who grew up in areas with higher levels of atmospheric lead showed "less adaptive" personalities in adulthood. This means they were less agreeable and conscientious. And if younger, they tended to be more neurotic.

To cross-check their findings, the researchers replicated the study using data from 37 European nations, where lead was phased out later than in the U.S. The results were similar—those with higher lead exposure in childhood were also less agreeable and more neurotic in adulthood, but not less conscientious.

Study author Ted Schwaba, PhD, a postdoctoral researcher at the University of Texas at Austin, tells Verywell, that he and colleagues also found that people born in the U.S. after the Clean Air Act of 1970 was passed were more mature and psychologically healthy. This law requires the Environmental Protection Agency (EPA) to establish nationwide air quality standards in accordance with the latest science.

Schwaba adds that he started studying lead exposure effects on personality to motivate change. "It's not like we have to be exposed to lead," he says. "If we continue to remove lead from the environment, we can potentially have happier, healthier, more organized, friendlier people."

The study was published in Proceedings of the National Academy of Sciences of the United States of America (PNAS) in late July.

How Does Lead Affect the Brain?

Simply put, Tomás R. Guilarte, PhD, dean of Robert Stempel College of Public Health and Social Work at Florida International University, tells Verywell, "lead inhibits a very important receptor in the brain that is critically important for brain development for learning and memory."

Guilarte was not involved in the study, but his own research looks at the neurotoxicity of chemicals like lead. Over time, he adds, this leads to weaker connections between neurons and a decrease in brain volume. As a result, the individual just isn't able to execute certain cognitive functions as well as others.

With such a large sample size, the data from this study shows power in numbers, Guilarte says.

"We've been studying lead neurotoxicity for about thirty years," he says. "To me, what is impactful about this study is the magnitude of the number of subjects."

However, Guilarte adds, we must recognize an important limitation of this study: It's only focused on the United States and Europe. "In many other parts of the world, the problem is even bigger," he says. "Africa, South America, the Middle East, Asia—that's where you get even higher levels of exposure."

Disparities in Who Is Exposed

For as much as policies like the Clean Air Act have reduced lead in the environment, it's still an urgent issue, particularly for people marginalized in society.

This kind of research can help us understand just how sinuous environmental justice issues are, Schwaba says. If you grow up to be less organized and more neurotic in part due to lead poisoning, for example, "that's a meeting you're going to miss today, maybe an assignment you're going to miss in school—there are effects that just snowball because these little things are affecting us constantly," he says.

"Back in the day, [leaded] gasoline was exposing everyone to lead," Schwaba says. "But the big issue now is that there are disparities in blood lead levels." Looking at recent data, one study found that Black children are at least 2.8 times more likely to have a clinically significant blood lead level than White children.

"It really sets up different groups of people, especially those who are already disadvantaged, to continue to have disadvantage across their whole lifespan," Schwaba adds. "So we really need to pay attention to these issues, even when they're not affecting the wealthier communities anymore, until there's lead removed for everybody."

Guilarte adds that if you look at the international data, you'll find that around 1 in 3 children, or up to 800 million globally, has blood lead levels at or above the clinically significant level of 5 micrograms per decilitre (µg/dL).

Lead Poisoning Can Be Prevented and Treated

The message to take away from this research, both Schwaba and Guilarte add, goes beyond individual risk and responsibility. It shows that entire societies are shaped by the consequences of exposure, until our systems collectively do something to stop it.

To prevent another downfall, Schwaba says that we can dedicate resources to removing lead pipes and lead paint from older homes, for instance.

On the other hand, Guilarte acknowledges that policy changes take a while. Fortunately, his 2003 research has shown that careful intervention can reverse some of the effects of lead poisoning in children. "There was a dogma that the effects of lead on the brain were irreversible," he says. "But we showed in fact that that's not the case. If you provide an enriched environment to lead-exposed children, you could improve their performance."

Guilarte and his colleagues have also developed research on a nutrient that mimics brain-derived neurotrophic factor (BDNF). When given to animals that have been lead-exposed, it reverses some of the neurological deficits produced. This chemical can be found in certain fruits like berries and is both safe and cheap.

"There are millions and millions of tons of lead, dispersed throughout the environment," Guilarte adds. "We need to reduce exposure, but sometimes that's not possible. So, we need to find other ways to help the individual become a better, more well-rounded person, and not be left behind because they've been exposed to this neurotoxin."