Lead mining began during the 7th century in Derbyshire, England. Magpie Mine was the last facility to operate in the region. It opened in 1735 and finally closed in 1954. Credit: Peter Thompson / Heritage Images / Getty Images

Thanks to some medieval human teeth , archaeologists have pinpointed when lead production first expanded across Europe during the Middle Ages. By examining dental enamel collected from graves located in central England, researchers now know the post-Roman society started mining and smelting again during the mid-7th century. As the team explains in a study published today in the journal Antiquity , the consequences of exposure to the toxic were stark—but distributed unequally among locals.

Humanity’s complicated relationship with lead dates back over 9,000 years, and our environmental exposure to the toxic metal is traceable as far as two million years ago .…