Hair samples over a century show how regulations cut lead exposure

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Lead is one of those public-health hazards that became “normal” for decades, until regulation forced it out of everyday products. Ars Technica reports that researchers at the University of Utah analyzed hair samples spanning nearly a century and found lead concentrations fell roughly 100-fold—evidence that the phase-out of leaded gasoline and other lead controls did what they were supposed to do.

The striking part isn’t just the trend line. It’s that the data comes from something mundane and personal: a strand of hair preserved in a family scrapbook.

Why lead was everywhere (and why it was so harmful)

For much of the 20th century, lead was used because it was useful:

  • In gasoline as tetraethyl lead, an “anti-knock” additive that improved engine performance
  • In paint and plumbing because it made materials easier to work with

But lead is a neurotoxin. Even low exposure can harm children’s cognitive development, and higher exposures can contribute to serious health problems across the lifespan.

Hair as a record of environmental exposure

Blood is the gold standard for measuring lead in the body, but hair has an advantage: it can capture exposure over time and can persist for decades.

Ars notes that lead can linger in air and settle on hair, where it accumulates—especially on the hair surface. Because modern mass spectrometry is very sensitive, researchers can analyze tiny samples, even single strands.

That makes hair useful for historical reconstruction. If families saved hair (or if samples were collected in earlier studies), you can build a timeline that blood tests can’t.

What the researchers found

According to Ars, the team saw very high hair lead levels in samples from roughly 1916 to 1969. After the 1970s, levels dropped steeply—down from around 100 parts per million to about 10 ppm by 1990, and under 1 ppm by 2024.

Those declines line up with the creation of the EPA in 1970 and subsequent restrictions that drove the phase-out of leaded gasoline and tightened controls on other lead sources. Ars also notes that the closing of regional smelting facilities likely contributed.

The policy lesson: “onerous” rules can have measurable payoffs

Environmental regulation often feels abstract until you can measure its impact on real bodies.

This study makes a concrete point: removing lead from the environment wasn’t just an ideological shift—it changed what people literally carried around in their tissues.

It also reframes debates about “deregulation.” Once exposure drops, it’s easy to forget how bad it was. Historical measurements are one of the few ways to keep that memory honest.

What this doesn’t prove (and what it still can’t answer)

Hair measurements are not the same as blood lead measurements. They don’t tell you exactly what the brain was exposed to at a given moment, and they can be influenced by external deposition.

But that limitation cuts both ways: if external deposition is part of the story, that’s still meaningful, because it reflects environmental lead in the air and dust people lived with.

Bottom line

A century of hair samples makes the success of lead regulation visible: after decades of high exposure, lead levels fell dramatically once leaded gasoline and other sources were restricted. The lesson is simple—when you remove a toxin from the environment, people stop carrying it around.

Sources

n English