A Century of Hair Samples Proves Leaded Gas Ban Worked
hubie writes:
The Environmental Protection Agency (EPA) cracked down on lead-based products-including lead paint and leaded gasoline-in the 1970s because of its toxic effects on human health. Scientists at the University of Utah have analyzed human hair samples spanning nearly 100 years and found a 100-fold decrease in lead concentrations, concluding that this regulatory action was highly effective in achieving its stated objectives. They described their findings in a new paper published in the Proceedings of the National Academy of Sciences.
We've known about the dangers of lead exposure for a very long time-arguably since the second century BCE-so why conduct this research now? Per the authors, it's because there are growing concerns over the Trump administration's move last year to deregulate many key elements of the EPA's mission. Lead specifically has not yet been deregulated, but there are hints that there could be a loosening of enforcement of the 2024 Lead and Cooper rule requiring water systems to replace old lead pipes.
"We should not forget the lessons of history. And the lesson is those regulations have been very important," said co-author Thure Cerling. "Sometimes they seem onerous and mean that industry can't do exactly what they'd like to do when they want to do it or as quickly as they want to do it. But it's had really, really positive effects."
[...] But his [Clair Patterson] many experimental findings on the extent of lead contamination and its toxic effects ultimately led to the rapid phase-out of lead in all standard automotive gasolines. Prior to the EPA's actions in the 1970s, most gasolines contained about 2 grams of lead per gallon, which quickly adds up to nearly 2 pounds of lead released via automotive exhaust into the environment, per person, every year.
Lead can linger in the air for several days, contaminating one's lungs, accumulating in living tissue, and being absorbed by one's hair. Cerling had previously developed techniques to determine where animals lived and their diet by analyzing hair and teeth. Those methods proved ideal for analyzing hair samples from Utah residents who had previously participated in an earlier study that sampled their blood.
[...] "The surface of the hair is special," said co-author Diego Fernandez. "We can tell that some elements get concentrated and accumulated in the surface. Lead is one of those. That makes it easier because lead is not lost over time. Because mass spectrometry is very sensitive, we can do it with one hair strand, though we cannot tell where the lead is in the hair. It's probably in the surface mostly, but it could be also coming from the blood if that hair was synthesized when there was high lead in the blood."
The authors found very high levels of lead in hair samples dating from around 1916 to 1969. But after the 1970s, lead concentrations in the hair samples they analyzed dropped steeply, from highs of 100 parts per million (ppm) to 10 PPM by 1990, and less than 1 ppm by 2024. Those declines largely coincide with the lead reductions in gasoline that began after President Nixon established the EPA in 1970. The closing of smelting facilities likely also contributed to the decline. "This study demonstrates the effectiveness of environmental regulations controlling the emissions of pollutants," the authors concluded.
Journal Reference: PNAS, 2026. DOI: 10.1073/pnas.2525498123
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