Scientists link childhood lead exposure to adult mental health problems

Lead contamination in drinking water has been linked to a host of health problems, from anemia and hearing loss to learning disabilities — especially in children. And now a growing body of evidence shows a connection between water polluted with lead and mental health problems.

Scientists have consistently found that there is no safe level of exposure to lead, yet roughly 186 million Americans are drinking water with lead levels above 1 part per billion — the level set by the American Academy of Pediatrics to protect children from lead in school water fountains.

Investigative reporter Kristina Marusic has been digging into the relationship between lead exposure and mental illness as part of a series on mental health and pollution for Environmental Health News. She focused her reporting on Western Pennsylvania, one of the worst regions in the country for lead contamination in water.

Related: An investigation has found lead in 2,000 US water systems

Marusic says scientists are beginning to figure out that, in addition to the learning, behavioral and cognitive problems in kids who are exposed to lead, the effects of lead exposure can show up as mental illness much later in life.

“[O]ne researcher who led a 2021 literature review…found increasing evidence that childhood lead exposure is a risk factor for psychiatric disorders in adulthood — including anxiety, depression, obsessive compulsive disorders.”

“I spoke with one researcher who led a 2021 literature review that looked at several dozen human and animal studies on lead exposure, and it found increasing evidence that childhood lead exposure is a risk factor for psychiatric disorders in adulthood — including anxiety, depression, obsessive compulsive disorders — and then also for neurodevelopmental disorders like ADHD, autism and Tourettes syndrome,” Marusic says.

The largest of those studies in this literature review looked at 1.5 million people in the US and Europe. It found that “people with higher lead exposure as children were more likely to have negative personality traits, like lower conscientiousness, lower agreeableness and higher neuroticism once they reach adulthood — all of which contribute to mental illness,” Marusic says.

Scientists have recently begun to pinpoint how lead exposure impacts the brain, Marusic notes. Lead exposure effects a protein receptor in the brain known as the NMDA receptor, which is critically important for brain development, learning and cognitive function, Marusic says.

“Improper functioning of the NMDA receptor is also seen in the brains of people with certain mental illnesses, including schizophrenia. The NMDA receptor influences the development of inhibitory neurons that help keep the brain balanced, and when it’s damaged by lead exposure, it creates too few of those neurons,” she explains.

Related: Childhood lead poisoning remains a widespread problem in America

In a healthy brain, excitatory neurons and inhibitory neurons occur in an “exquisite balance where there are an equal amount of both,” Marusic says. If this balance is disturbed or interrupted, that can manifest as mental illness.

Communities where childhood lead exposure is a problem are also likely to experience other issues that can disproportionately affect people’s health, Marusic notes. These include environmental exposures like air pollution and other hardships like community violence, racism and poverty.

“[T]here’s also emerging evidence that one harmful exposure from something like air pollution changes the brain in a way that can magnify the effects of another harmful exposure later on.”

“All of these factors kind of overlap to create combined physical and mental health impacts that can be really detrimental,” Marusic says. “But there’s also emerging evidence that one harmful exposure from something like air pollution changes the brain in a way that can magnify the effects of another harmful exposure later on.”

“It definitely is an environmental justice issue,” Marusic adds. “If you look at many of the communities that have made headlines for having lead in the drinking water, many of them are majority Black communities. So this is a story we see play out again, and again in the United States.”

Related: Newark, NJ, has a lead contamination problem in its water

Replacing lead pipes in a community or across an entire city is hugely expensive. Cities and municipalities are often strapped for cash and don’t have the budget to do it. And replacing just part of a lead line, and not the entire water line leading to a home or other structure, can temporarily result in more lead in the water, Marusic points out. Most water authorities are therefore required to do a full lead line replacement at no cost to the homeowners.

“If they’re replacing the line under the street, they also have to replace the lines that go into everyone’s homes at the same time,” Marusic explains. “And if there’s a delay, if initially they replaced the part in the street, they also have to notify people that they should use a filter to make sure that they’re not getting exposed to extra lead when it’s kind of jostled loose during that process.”

President Biden initially sought $45 billion from Congress to help cities and municipalities replace lead pipes, but only $15 billion made it into the infrastructure bill he signed into law late last year.

Biden included additional money for lead pipe replacement in his Build Back Better plan, but that plan is currently stalled in Congress, due to the opposition of all 50 Republican senators and Democratic Senator Joe Manchin of West Virginia.

This article is based on an interview by Bobby Bascomb that aired on Living on Earth from PRX.