When do you think the earliest man-made air pollution was? Most think it was during the industrial revolution, but in actuality, there is evidence from before then of air pollution by man. Research done by Ohio State found residue of pollution in 2003, on the Quelccaya ice cap. In the 16th century, during the Spanish’s conquest of South America, the Spanish empire forced thousands of Inca’s to extract silver from the mountaintop mines of Potosí. In 1572, the Spanish invented a machine that would increase production. It did just that, though at the same time send thick clouds of lead dust into the sky. An online edition of Proceedings of the National Academy of Sciences reports a layer underneath the Quelccaya ice cap that dates back to the conquest of the Inca. This layer supports that there was human-produced air pollution before the industrial revolution.