STUDY: Lead Exposure Decades Ago Could Be Causing Memory Problems Now

Lead is toxic to the human brain, even at low levels. Decades ago, scientists saw that high levels of lead in the atmosphere had an impact on childhood brain development. Now, it’s becoming clear that impacts of lead exposure may stick around for decades, bringing about memory problems and broader cognitive health issues later in life. That’s what’s emerging from the data in three new studies presented at the 2025 Alzheimer’s Association International Conference in Toronto this week. 

Early research shows it may even predispose the brain to Alzheimer’s disease. 

Lead became prevalent in the environment after leaded gasoline was introduced in the 1920s, up to its peak use in the 1960s and ‘70s. Products like leaded gasoline and lead paint have since been phased out. But some manufacturing processes still release lead into the environment today. And recent policy rollbacks mean lead exposure could become more of a public health threat.

The long-tail effects of lead exposure on brain health

Eric Brown, a psychiatrist who specializes in treating older adults at the Center for Addiction and Mental Health in Canada, mapped out historical lead levels across the U.S. during the peak of leaded gasoline usage. He and his colleagues linked the levels of lead exposure to the prevalence of self-reported memory problems using census data of 644,684 older adults who had lived in the same state since childhood. (The researchers could not control for the effects of people moving between cities within the same state, which might have vastly different lead levels.)

What they found was that people who lived in areas with moderate, high, or extremely high atmospheric levels of lead during their childhood had a 17- to 22-percent higher chance of self-reporting memory problems.

People concerned about lead levels in their
area can check if they live near an
active lead-releasing facility here.

“Exposures from the past may have long and latent impacts on people decades down the road,“ Brown told Being Patient. “With dementias and cognitive impairment, we need to think about someone’s entire life course to understand the risk factors and the places to intervene.”

There are other factors that may have influenced the results: Alongside lead, vehicles also released other small pollutants found in gasoline or diesel exhaust into the air. Brown and his colleagues are planning an additional study to understand how these pollutants affect memory.

How lead exposure could make way for Alzheimer’s disease

Large, population-level studies have linked lead exposure to worse cognitive outcomes. Researchers are taking a closer look at brain cells to see how these metals might make the brain more vulnerable to cell death and Alzheimer’s. 

Junkai Xie, a researcher at Purdue University, measured how brain cells in a dish responded to different levels of lead. Unlike previous studies, he and his colleagues actually exposed human brain cells in a dish to low doses of lead, mirroring the exposure levels people might experience. The U.S. Environmental Protection Agency (EPA) considers any lead amount in water higher than 15 parts per billion (15-ppb) a cause for concern. Xie’s team exposed the cells to 0, 15, and 50 ppb to see how they responded.

The 15- and 50-ppb doses led to profound changes in the brain cells: They became abnormally electrically active and couldn’t produce energy efficiently, which might impair their ability to function, and contribute to cell death. Lead exposure also increased the levels of tau and beta-amyloid plaques, both markers of dementia, in the brain cells. Even after researchers removed the lead, the cells remained more vulnerable to future damage and stressors — which means the unhealthy effects of lead may linger long after exposure ended.

“There are certain chemical exposures that can cause harm to human health later on,” said Xie. Studying how chemicals like lead affect brain function could help scientists identify new targets for treatment. For example, if lead affects a specific protein in the brain that’s required to make energy efficiently, scientists could test treatments that fix the problem by boosting the function of this protein.

Lead-releasing facilities and health risks

Lead exposure isn’t just a problem of the past. In cities like Flint, Michigan, older pipes leach lead into drinking water. There are also more than 7,500 lead-releasing facilities — such as those involved in manufacturing glass, ready-mixed concrete, or computers and electronics — that were active in the U.S. in 2023.  

Kathryn C. Conlon, epidemiologist at the University of California, Davis followed 2,379 ethnically diverse older adults living in Northern California. Those who lived within five kilometers (around three miles) of these facilities scored worse on tests measuring memory and cognitive function than those living farther away. 

While most people might imagine that these facilities are located in remote areas, far from population centers, that isn’t the case: “Most of the lead-releasing facilities were located in communities that were greater than 100,000 people,” Conlon told Being Patient. 

But the study only captured one snapshot in time: Conlon and her colleagues intend to follow up and see whether living near one of these facilities could accelerate cognitive decline. 

“We don’t have to be exposed to lead,” said Conlon. “It’s something that can be eliminated from most of our environment if we had policies in place that protected us.”

Policy rollbacks and lead exposure

As researchers present studies on the harms of lead exposure, the EPA is planning to roll back and narrow regulations that limit the release of lead and other heavy metals into the environment by power plants. Researchers and policy experts are concerned that these actions would increase exposure.

Another one of these regulations facing rollbacks and modifications is the Clean Water Act, which reduces pollutant release into wastewater by coal-fired power plants by “584 million pounds per year.” The EPA intends to limit which waterways are protected by this act.

Kate Robb, the deputy director of the Center for Public Health Policy at the American Public Health Association, told Being Patient that the APHA and other environmental health professionals are “concerned.” Staffing cutbacks to the National Center for Environmental Health at the Centers for Disease Control, she said, will also affect the ability of the lead prevention team to address lead exposure in communities.  

“I think people would be surprised to learn that they likely live within close distance to a facility that is releasing lead,” said Conlon.

Beyond changes in policy or moving to a new neighborhood, there are limited ways to mitigate lead exposure on an individual level. Conlon suggests people who live near these facilities should keep their house clean of dust that might become contaminated with lead, remove their shoes when coming inside, and use doormats to avoid tracking in lead-contaminated dust.

“There’s no safe level of lead exposure,” said Robb. These regulatory rollbacks are “sending a message to polluters that they won’t be held accountable for endangering lives in our community.” People concerned about lead levels in their area can check if they live near an active lead-releasing facility here.