"Hair is really a vault of information, says Ken Smith, a demographer at the University of Utah. He should knowhe's among a team of scientists that analyzed chemicals found in hair samples collected over the course of more than a century in research published on February 2 in Proceedings of the National Academy of Sciences USA. Incredibly, Smith and his colleagues found that exposure to leada dangerous heavy metalhas fallen by a factor of more than 100 since the 1960s."
"The analysis didn't distinguish between lead in the sheathlike cuticle that surrounds a hair and that found in the hair itself. The former would have been picked up from contaminated air, and the latter would have stemmed from the consumption of contaminated food or water. The trend over time is stunning. Peak lead rates occurred in samples from the 1960s, when lead was enriched by some 120 times compared with 20202024 samples."
Researchers analyzed 47 hair samples dated 1916–2024 from the greater Salt Lake City region to measure lead content. Analysis did not distinguish between lead on the cuticle from air contamination and lead inside hair from ingested food or water. Peak lead levels occurred in samples from the 1960s, with enrichment roughly 120 times that of 2020–2024 samples. Lead exposure rates steadily declined after the 1960s. The decline occurred alongside formation of the Environmental Protection Agency in 1970 and passage of the Clean Air Act and Clean Water Act in that decade. Locks of hair stored for decades can reveal environmental change over time.
Read at www.scientificamerican.com
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