Study of Lead in Hair Shows Big Decline Since 1970s ^{CEFR B2}

Researchers analysed human hair to reconstruct lead exposure in people who lived along Utah's Wasatch Front over roughly a century. They collected samples from 48 individuals, combining contemporary hair and older strands kept in family scrapbooks dating back to 1916. The region once hosted smelting plants in Midvale and Murray that produced heavy local emissions, and the team linked much early exposure to leaded gasoline.

The analysis was done with mass spectrometry at a University of Utah facility directed by Diego Fernandez. Mass spectrometry is sensitive enough to detect lead in a single hair strand, though it cannot always distinguish lead on the hair surface from lead incorporated during hair growth. Blood remains a better measure of recent internal exposure, but hair is easier to collect and preserves older exposures.

The paper, published in PNAS, reports that hair lead concentrations fell from as high as 100 parts per million to 10 ppm by 1990 and to less than 1 ppm in 2024. The authors note that before EPA regulations, lead levels were about 100 times higher than after the rules. They point out that, before 1970, leaded gasoline contained about 2 grams of lead per gallon, which the authors say amounted to nearly 2 pounds of lead released into the environment per person each year.

Coauthor Thure Cerling and demographer Ken Smith said the results show the value of environmental regulation. The paper also notes that lead rules were weakened by the Trump administration. Support for the study came from the Huntsman Cancer Foundation and the National Cancer Institute through a grant to the Utah Population Database and the University of Utah.