Most people think of lead pollution as a modern problem.
A result of adding the toxic metal to the petrol we burn in our cars or the pigments added, until recently, to paint and other products. In fact lead pollution is nothing new. Over the last decade, scientists have been studying natural systems that preserve a record of past air quality to try to chart the build up of toxic metals like lead in the atmosphere as a result of human activity. Investigations have considered records preserved in lake sediments and peat bogs and, perhaps most comprehensively, in cores taken through the ice of Greenland's frozen interior. The Greenland ice cores allow us to measure the background of natural lead in the atmosphere thousands of years ago, before humans had developed the art of metallurgy and the use of metals.