In this episode, Thure Cerling, professor of geology at the University of Utah, discusses new research showing that environmental lead exposure in the United States has declined dramatically over the past century. The findings, published in the Proceedings of the National Academy of Sciences, demonstrate how policy decisions translated directly into measurable public health improvements.
Cerling and his colleagues analyzed hair samples dating back to 1916 and found steep declines in lead levels beginning in the 1970s, coinciding with Environmental Protection Agency regulations that phased out leaded gasoline and reduced lead in paint, pipes and consumer products. Even as fuel consumption increased over time, human lead exposure dropped sharply.
Hair acts as a long-term environmental record, preserving evidence of past exposure. In Utah, preserved locks of hair kept in family scrapbooks and heirlooms provided researchers with a rare historical archive. The samples allowed scientists to trace how communities along the Wasatch Front — once affected by smelting operations and tailpipe emissions — experienced a century of changing environmental lead levels.
The research underscores the effectiveness of environmental regulation and offers a clear example of how science and public policy can work together to protect public health.
