Quantifying and assessing the impacts of heavy metal flows: Fate, transport, and impacts of lead use in United States product manufacturing.

摘要

Heavy metals, such as lead, are toxic, yet despite awareness of this toxicity, they are used throughout the global economy. Eliminating their use would reduce risk, but they have useful physical and chemical properties and suitable substitutes have proven difficult to find. For example, due to previous investigations of lead's toxicity, it was removed as a gasoline additive in the US and other countries beginning in the 1980s. However every automobile and truck shipped contains a lead-acid battery, and many other products still contain lead. For decision makers, being able to better link the flows and uses of lead with the potential human health and ecotoxicity impacts of its release is an important goal.; This dissertation seeks to contribute to this need by developing methods to dynamically track lead flows throughout the economy, and also to link the flows with eventual impact. This is accomplished by the creation of various mixed-unit input-output models of lead and lead compounds in the US economy, at various levels of aggregation (from 12 to approximately 100 sectors). For the latter, a dynamic lead flow model was created to aid in tracking the flows of lead to various media over a 15 year timeframe, 1990 to 2004. The United States' Toxics Release Inventory (TRI) tracks releases to various media of both lead and lead compounds, and this data is a key input into the methods used. These models allow decision makers to recognize which sectors are the sources of the greatest direct and total lead and lead compound emissions.; Beyond tracking lead flows, this dissertation also links lead flows with impacts. To this end, impact assessment values for lead and lead compounds from two well known impact assessment methods, CalTox and the U.S. Environmental Protection Agency's Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) model, were used.; The results of the impact assessment suggest that the parameters of CalTox, as used in TRACI, may lead to underestimates of the actual concentrations of lead in the environment. Thus decision makers focused on lead and other heavy metals should explore other impact assessment methods to ensure that the impacts of these substances are better understood.