Exploitation of the extensive polymetallic deposits of the Andean Altiplano in South America since precolonial times has caused substantial emissions of neurotoxic lead (Pb) into the atmosphere; however, its historical significance compared to recent Pb pollution from leaded gasoline is not yet resolved. We present a comprehensive Pb emission history for the last two millennia for South America, based on a continuous, high-resolution, ice core record from Illimani glacier.

Carbon-based liquid fuels are highly valued for transportation; they are the world's largest form of commercial energy and second largest source of anthropogenic carbon dioxide (CO2) emissions. Strategies to address their CO2 emissions have been shaped by fuel cycle analysis (FCA), a version of lifecycle assessment that examines fuel products and their supply chains. FCA studies have diverse findings and large uncertainties. Disagreements are particularly sharp for biofuels, which are seen as key replacements for petroleum fuels.