Apr. 30, 2013 — A team of scientists find in the Laguna de Rio Seco lagoon, at an altitude of 3,020 m., evidence of atmospheric pollution caused by lead and linked to metallurgical activities from 3,900 years ago (Early Bronze Age). Lead pollution increased gradually during the Late Bronze Age and Early Iron Age, coinciding with the development and expansion of metallurgy in southern Europe.
http://www.sciencedaily.com/releases/2013/04/130430092325.htm