Scientists at the University of Utah have used preserved hair samples to trace a dramatic decline in lead exposure among Americans over the past century, linking it directly to environmental regulations introduced in the 1970s. The study shows lead levels in hair were about 100 times higher before the EPA's formation than after. This historical record underscores the public health benefits of curbing lead from sources like gasoline and paint.
Lead pollution was once ubiquitous in the United States, stemming from vehicle exhaust, factories, lead-based paint, and water pipes. A new study published in the Proceedings of the National Academy of Sciences (PNAS) in 2026 documents how exposure to this toxic metal plummeted following stricter environmental rules.
Researchers analyzed hair samples from 48 individuals along Utah's Wasatch Front, an area with a history of heavy industrial activity, including smelting. The samples, some preserved in family scrapbooks dating back to 1916, provided a timeline of lead accumulation. Using mass spectrometry, the team measured lead concentrations, finding levels as high as 100 parts per million (ppm) before 1970, dropping to about 10 ppm by 1990 and less than 1 ppm by 2024.
"We were able to show through our hair samples what the lead concentrations are before and after the establishment of regulations by the EPA," said Ken Smith, a demographer and distinguished professor emeritus at the University of Utah. "We have hair samples spanning about 100 years. And back when the regulations were absent, the lead levels were about 100 times higher than they are after the regulations."
The decline mirrors the phase-out of leaded gasoline, which contained around 2 grams of lead per gallon before 1970. This resulted in nearly 2 pounds of lead entering the environment per person annually through exhaust. The EPA, established under President Richard Nixon in 1970, enforced limits on lead in gasoline, paint, and plumbing, leading to sharp reductions despite rising fuel use.
Co-author Thure Cerling, a professor of geology and biology, emphasized the regulations' impact: "We should not forget the lessons of history. And the lesson is those regulations have been very important." He noted that while lead offered practical benefits, such as improving engine performance and paint durability, its health risks—including developmental issues in children—necessitated action.
The study highlights hair's value as a preserved record of environmental exposure, though it reflects overall levels rather than precise blood concentrations. Funded by the Huntsman Cancer Foundation and the National Cancer Institute, the research originated from aging studies involving Utah residents.
