For much of the 20th century, Europeans and Americans have been surrounded by lead. Our drinking water ran through lead pipes, we played with toys covered in lead paint and we put it in cars which pumped it out onto our streets.
Now, a new study from University of Utah offers evidence of just how dramatically that exposure has fallen: lead levels in human hair have dropped by roughly 100 times over the past century.
The findings are based on hair samples from Utah residents spanning more than 100 years, some dating back to 1916.
Ken Smith, a distinguished professor emeritus at the University of Utah and a lead author on the study. said: ‘We were able to directly compare lead levels before and after environmental regulations were put in place. Before those rules existed, the lead levels were about 100 times higher than what we see today.’
Lead is a powerful neurotoxin that builds up in the body and is especially harmful to children, where it has been linked to developmental and cognitive problems.
Lead was widely used because of its useful chemical properties and was added to petrol to improve engine performance, the direct consequence of which was that tons of the metal was sent into the air through exhaust.
That began to change in the 1970s, when growing evidence of lead’s dangers prompted a widespread phase out from its use in petrol and other consumer products.
To see how those policies translated into lower exposure for people, the Utah researchers turned to hair. Using highly sensitive mass spectrometry, they measured lead concentrations in samples provided by 48 people. Some samples came from participants’ childhoods, while others were recovered from family scrapbooks and keepsakes preserved by relatives decades earlier.
Diego Fernandez, a research professor of geology and geophysics who oversaw the laboratory analysis said: ‘The surface of hair tends to accumulate lead, and importantly, it doesn’t lose it over time. That makes hair a surprisingly reliable record of environmental exposure.’
The study focuses on Utah’s Wasatch Front, an area that once hosted a major smelting industry in cities such as Midvale and Murray. Those facilities, along with vehicle emissions, contributed to heavy local pollution through much of the 20th century.
The results show a sharp decline after the 1970s. Lead levels in hair fell from as high as 100 parts per million before regulation to about 10 parts per million by 1990. By 2024, levels were below 1 part per million.
Co-author Thure Cerling, a distinguished professor of geology and biology, said the findings offer a clear reminder of the impact of environmental rules. ‘Sometimes regulations feel burdensome,” he said, “but the benefits to public health have been enormous.’
The full research can be read here.
Photo: Austrian National Library
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