Researchers examined old hair specimens, involving those taken from an infant (right) and an adult (left), to ascertain their lead content.(Image credit: Diego Fernandez)Share by:
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Humankind has deemed lead beneficial for millennia, yet the metal’s detrimental consequences weren’t widely acknowledged until the 20th century. Now, leveraging prior hair examples, scientists have demonstrated that regulations aimed at controlling heavy-metal contamination were greatly successful in minimizing the public’s susceptibility to lead once its hazards became known.
“We possess hair samples covering approximately 100 years,” conveyed study co-author Ken Smith, a population expert at the University of Utah, in an announcement. The research concentrated on people residing in Utah.
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In the fresh research, distributed Monday (Feb. 2) in the PNAS journal, the scientists expounded on their examination of hair strands from 47 subjects who dwelt in the Greater Salt Lake City locale both during their childhood and adult periods. Study volunteers furnished portions of their infantile hair, preserved within family albums, in conjunction with a present-day hair sample. The scientists scrutinized the hair’s lead content employing mass spectrometry, a methodology for recognizing chemical elements within a specimen.
Lead assimilation poses a detriment to human wellness, triggering harm to the neurological structure, potentially leading to developmental setbacks, convulsions, and scholastic impediments, while concurrently elevating the susceptibility to fertility complications and elevated blood pressure. As the scientists documented in their article, there exists no known safe benchmark for lead vulnerability.
A noteworthy origin of noxious lead exposure in the initial segment of the 20th century involved leaded fuel. In the 1920s, tetraethyl lead — a compound uniting carbon and lead — was incorporated into gasoline to curtail engine “knocking,” the tapping sound resultant from premature fuel ignition. Despite the U.S. Public Health Service realizing as early as 1925 that leaded fuel was engendering health issues, the fuel additive wasn’t definitively prohibited in the U.S. until 1996.
Nonetheless, pivotal mandates concerning lead were instituted before the 1990s. The U.S. Environmental Protection Agency (EPA), conceived by then-President Richard Nixon in 1970 to tackle diverse airborne and pollution quandaries, precipitated a swift diminution in lead contact, as the scientists observed in their current study.
Lead densities within human hair hailing from the Salt Lake City expanse registered as exceedingly high from 1916 to 1969, partly due to the absence of EPA regulation and partially owing to a pair of operational lead smelter locations within the vicinity. However, spanning from the 1970s to the 1990s, subsequent to the EPA’s formation and the smelters’ closure, the average indices receded by a factor of one hundred.
The U.S. Mining and Smelting Co. facility in Midvale, Utah, captured photographically in 1906.
“Prevailing lead levels in hair from this populace register, on average, nearly 100 times below those predating the establishment of the Environmental Protection Agency,” the scientists documented.
One reservation pertains to the lack of precise correlation between the lead concentrations in hair and the levels circulating within the bloodstream, which constitutes doctors’ standard parameter for pinpointing subjects necessitating lead toxicity intervention.
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As highlighted by study co-author Thure Cerling, a geologist affiliated with the University of Utah, a hair sample “doesn’t definitively register that internal blood concentration perceived by your cerebrum, although it elucidates that comprehensive environmental exposure.” Consequently, the research generally indicated that people were absorbing a substantially augmented lead quantity antecedent to 1970.
“It simply ejects from the exhaust pipe, ascends into the atmosphere, and subsequently descends,” Cerling clarified. Lead persists within the atmosphere for extended durations, “assimilating into your hair, infiltrating your lungs through inhalation.”
The scientists indicated that while their analysis corroborates the efficaciousness of ecological mandates in curbing detrimental contaminants like lead, these very regulations now confront the potential for retraction.
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Specifically, the scientists highlighted a March 12, 2025, pronouncement by the EPA and President Donald Trump that would relax numerous EPA stipulations currently safeguarding the provision of pristine air, terrain, and hydration for U.S. inhabitants. Despite the absence of explicit lead pollution mention, specialists have posited that the pronouncement furnishes a “blueprint” for rescinding regulations concerning atmospheric contamination stemming from the manufacturing domain and wastewater sourced from coal installations, among other aspects. Already, a minimum of one federal suit has been lodged aiming to overturn “presidential waivers” concerning the EPA’s Clean Air Act.
“We shouldn’t overlook the historical context,” Cerling advised. “These ordinances have carried substantial significance,” as underscored by the EPA’s demonstration of “truly, genuinely favorable impacts” soon following its inception.
The prior hair examination showcases that relaxed ecological benchmarks in previous eras culminated in unhealthful lead thresholds, yet these levels remain manageable through “science-derived guidelines,” the scientists concluded.
Article Sources
Cerling, T.E., Fernandez, D.P., & Smith, K.R. (2026). Lead in archived hair documents a decline in lead exposure to humans since the establishment of the US Environmental Protection Agency. PNAS, 123, e2525498123. https://doi.org/10.1073/pnas.2525498123
IN CONTEXT
IN CONTEXTNicoletta LaneseHealth Channel Editor
At present in the U.S., lead susceptibility typically embodies the greatest menace within low-income neighborhoods and in Northeast and Midwest metropolitan areas possessing older habitations — specifically, edifices erected prior to 1978, the timeline for the prohibition of lead-centered paints. Additional prevalent origins of contact encompass soil tainted by earlier lead sources, such as mining operations; compromised pipes and plumbing materials; polluted jewelry, playthings, or sweet treats; in conjunction with lead residue tracked into domiciles originating from workplaces. Offspring under the age of 6 exhibit amplified vulnerability to lead affliction, attributed to their developing systems absorbing the metal exceedingly efficiently.
Periodic table of elements quiz: How many elements can you name in 10 minutes?TOPICSunited states
Kristina KillgroveSocial Links NavigationStaff writer
Kristina Killgrove functions as a staff scribe at Live Science, emphasizing reports pertaining to archaeology and paleoanthropology. Her compositions have additionally surfaced in locations encompassing Forbes, Smithsonian, and Mental Floss. Kristina maintains a Ph.D. in biological anthropology alongside an M.A. in classical archaeology derived from the University of North Carolina, coupled with a B.A. in Latin secured from the University of Virginia; furthermore, she previously held positions as a university instructor and researcher. Her acknowledgements encompass accolades bestowed by the Society for American Archaeology as well as the American Anthropological Association for her science-oriented writings.
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