One of the major findings of this project, and others preceding it, was that there was a distinct increase in atmospheric pollutants starting around 500 BC. Atmospheric quantities of lead, silver, and copper then increased steadily, reaching a peak in the first century AD. Remarkably, this atmospheric quantity of lead is reached again only in the thirteenth century. These findings show how intense, compared with what came before and after, Roman mining was. This upsurge in mining clearly indicates economic expansion.
