For those who grew up in the 1960s or 1970s, a new study highlights a troubling link between past environmental exposure and brain health: high levels of atmospheric lead during that era may raise the risk of memory problems in later life by 20%.
Leaded gasoline, widely used in the U.S. from the 1920s until its gradual phase-out starting in the 1970s (and full ban in 1996), was once prized for improving engine performance and reducing “knocking.”
However, decades of research have uncovered its severe toxicity—particularly to developing brains and nervous systems, causing developmental, learning, and behavioral issues in children, as well as neurological and reproductive problems in adults. Soil and water contamination from leaded gas also persists as a legacy issue.
The new study, presented at the Alzheimer’s Association International Conference (AAIC) in Toronto, builds on this understanding.
Researchers from the University of Toronto mapped historic atmospheric lead levels in the U.S. between 1960 and 1974—a period when leaded gas use peaked—and compared them to self-reported memory difficulties among over 600,000 adults aged 65 and older from 2012 to 2021 (only those living in their birth state were included).
Their findings are stark: 17% to 22% of individuals in areas with moderate, high, or extremely high atmospheric lead levels reported memory problems. This aligns with broader data: Maria C. Carrillo, chief science officer of the Alzheimer’s Association, noted that research suggests over 170 million Americans—half the population—were exposed to high lead levels in early childhood.
Esme Fuller-Thomson, senior study author and director of the Institute for Life Course and Aging at the University of Toronto, emphasized the scale of past exposure: “When I was a child in 1976, our blood carried 15 times more lead than children’s blood today. An astonishing 88% of us had levels higher than 10 micrograms per deciliter, which are now considered dangerously high.”
Compounding concerns, other research presented at AAIC revealed additional risks: even low lead exposure can contribute to the buildup of tau and amyloid beta proteins—hallmarks of Alzheimer’s disease—in brain cells.
Another study found that older adults living within 3 miles of lead-releasing facilities (such as glass, concrete, or electronics manufacturers) face greater odds of memory and thinking issues than those farther away.
Unfortunately, measuring long-term lead exposure is challenging. Blood lead levels reflect only recent or ongoing exposure, while lead stored in bones—measurable via K-X-ray fluorescence—is primarily a research tool, not widely available clinically.
For those worried about past lead exposure, researchers recommend mitigating other dementia risk factors, such as high blood pressure, smoking, and loneliness. As Kathryn Conlon, an associate professor of environmental epidemiology at UC Davis and senior author of a related AAIC study, noted: “Despite tremendous progress on lead abatement, studies have shown there is no safe level of exposure, and half of U.S. children still have detectable levels of lead in their blood.”
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