R. P. Mason, in Still Only One Earth: Progress in the 40 Years Since the First UN Conference on the Environment, ed. R. M. Harrison and R. E. Hester, The Royal Society of Chemistry, 2015, pp. 107-149.
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While both lead (Pb) and mercury (Hg) are not abundant in the Earth's crust, they are two trace elements that have largely impacted human health because of their enhancement in the biosphere due to human activity. Their global cycles have been altered by humans as both Pb and Hg have been used for thousands of years. Current inputs to the atmosphere for Hg are a factor of 5–6 times higher than pre-anthropogenic emissions. The inputs at the time of heightened use of Pb in gasoline (1960–1980's) were much larger relative to the pre-industrial flux. However, as emissions of Pb have been strongly curtailed due to regulation of their use in gasoline, paints and many other applications, the current inputs to the atmosphere are much lower, even given the heightened recent industrial activity in Asia and elsewhere. This is not the case for Hg, as emissions have not decreased over the last 20 years, although now the major emissions are from Asia, whereas previously they were from the western world. The impact of anthropogenic activity is recorded in various archives, and impacts have been documented by changing concentrations in the oceans and terrestrial environment. The success of various policy initiatives are highlighted as well as the impact of emissions and also regulation of these activities on human health.
