BOB HIRSHON (host):
Prehistoric lead pollution. I’m Bob Hirshon and this is Science Update.
Researchers in Spain have found evidence of man-made lead pollution – as far back as 3,900 years ago. The evidence comes from sediments in an alpine lake. According to paleontologist Gonzalo Jimenez Moreno, the sediments’ chemistry reveals periodic spikes in atmospheric lead – starting in the Bronze Age, when humans there first started mining. To isolate metals, they’d burn away the surrounding rock, releasing other elements like lead in the process.
GONZALO JIMENEZ MORENO (University of Granada, Spain):
So in order to obtain the copper, which is what they really wanted to obtain, there’s always lead that goes into the atmosphere. This process is called smelting.
Other peaks occurred during the Roman Empire, and of course, the modern Industrial Revolution. One bit of good news: after hitting record highs, lead levels recently started declining again, presumably because of measures like banning leaded gasoline. I’m Bob Hirshon for AAAS, the Science Society.