TORONTO, July 27, 2025 — Adults who grew up breathing airborne lead are about 20% more likely to experience memory issues later in life, according to three studies presented at the Alzheimer’s Association International Conference. These findings suggest a lingering impact of environmental lead exposure on cognitive health across the lifespan.
- Adults exposed to airborne lead as children are about 20% more likely to have memory problems.
- Living near lead-releasing facilities correlated with lower memory and cognitive scores in adults.
- Lead exposure in neurons showed signs of dysfunction and vulnerability to Alzheimer’s-related stressors.
“Research suggests half the U.S. population, more than 170 million people, were exposed to high lead levels in early childhood,” said Maria C. Carrillo, PhD, chief science officer and medical affairs lead for the Alzheimer’s Association, in a press release. “This research sheds more light on the toxicity of lead related to brain health in older adults today.”
### Leaded Gas and Lingering Effects
One study analyzed historical atmospheric lead levels (HALLs) across the United States from 1960 to 1974, a period coinciding with extensive leaded gasoline use. Leaded gasoline was phased out in the U.S. starting in 1975.
“When I was a child in 1976, our blood carried 15 times more lead than children’s blood today,” said Esme Fuller-Thompson, PhD, director of the Institute for Life Course and Aging at the University of Toronto. “An astonishing 88% of us had levels higher than 10 µg/dL, which are now considered dangerously high.”
Researchers categorized HALLs into low (<0.4 µg/m³), moderate (0.4-0.79 µg/m³), high (0.8-1.19 µg/m³), and extremely high (≥1.2 µg/m³). Data from the American Community Survey (2012-2017 and 2018-2021) on self-reported memory problems among adults aged 65 and older showed that those living in areas with moderate to extremely high HALLs were approximately 20% more likely to report memory issues compared to those in low-exposure areas. The findings suggest that the significant decrease in atmospheric lead exposure in the late 20th century may contribute to declining dementia rates today. "Our study may help us understand the pathways that contribute to some people developing dementia and Alzheimer’s disease," stated Eric Brown, MD, MSc, FRCPC, associate chief of geriatric psychiatry at the Centre for Addiction and Mental Health in Toronto. ### Proximity to Pollution A second study focused on the cognitive function of 2,409 individuals (average age 74) and their proximity to lead-releasing facilities. Participants lived, on average, 6.6 kilometers from such facilities. The research found that for every 5-kilometer decrease in distance from a facility, participants showed a 0.07 decrease in verbal episodic memory and a 0.09 decrease in semantic memory two years later. Those living within 6 kilometers of a facility experienced even greater declines. "Our results indicate that lead exposure in adulthood could contribute to worse cognitive performance within a few years," said Kathryn Conlon, PhD, MPH, an associate professor of environmental epidemiology at the University of California, Davis. "Despite tremendous progress on lead abatement, studies have shown there is no safe level of exposure, and half of U.S. children have detectable levels of lead in their blood." Conlon emphasized the importance of keeping homes clean to reduce lead dust exposure for those living near the approximately 7,507 facilities that released lead in the U.S. in 2023. ### Neuronal Impact The third study delved into the cellular mechanisms, examining lead concentrations in cortical neurons derived from human-induced pluripotent stem cells. Researchers observed that while neurite morphology remained largely intact, lead-exposed neurons exhibited significant hyperactivity and mitochondrial dysfunction. Specifically, neurons exposed to 15 ppb and 50 ppb of lead showed increased electrical activity, indicating early dysfunction, and damage to energy-producing cells. "These findings help explain how lead exposure, especially in early life or from occupational and environmental sources, might leave a lasting molecular imprint on the brain, making it more vulnerable to age-related diseases like Alzheimer’s," noted Junkai Xie, PhD, a postdoctoral research associate at Purdue University. The study also found that lead exposure was linked to increased levels of phosphorylated Tau, Tau aggregates, and amyloid-beta 42/40 ratios—key biomarkers for Alzheimer's disease. Additionally, lead-exposed neurons were more susceptible to stressors associated with Alzheimer's, such as paired helical filament-Tau and the mitochondrial toxin 1-methyl-4-phenylpyridinium. These vulnerabilities persisted even after lead removal. "Our results show that lead exposure isn’t just a short-term concern," Xie added. "It may set the stage for cognitive problems decades later." The researchers suggest that understanding these molecular pathways could lead to interventions for individuals exposed to lead.
