This report summarizes the approach to be rollowed when evaluating the natural attenuation or MTBE and other fuel oxygenate and considers the consequences or the unique physical and chemical characteristics and their resultant behavior in the environment.

This slide presentation summarizes the approach to be followed when evaluating the natural attenuation or MTBE and other fuel oxygenate and considers the consequences or the unique physical and chemical characteristics and their resultant behavior in the environment.

In the past decade, officials responsible for clean-up of contaminated groundwater have increasingly turned to natural attenuation-essentially allowing naturally occurring processes to reduce the toxic potential of contaminants-versus engineered solutions. This saves both money and headaches. To the people in surrounding communities, though, it can appear that clean-up officials are simply walking away from contaminated sites. When is natural attenuation the appropriate approach to a clean-up? This book presents the consensus of a diverse committee, informed by the views of researchers, regulators, and community activists. The committee reviews the likely effectiveness of natural attenuation with different classes of contaminants-and describes how to evaluate the "footprints" of natural attenuation at a site to determine whether natural processes will provide adequate clean-up. Included are recommendations for regulatory change. The committee emphasizes the importance of the public's belief and attitudes toward remediation and provides guidance on involving community stakeholders throughout the clean-up process. The book explores how contamination occurs, explaining concepts and terms, and includes case studies from the Hanford nuclear site, military bases, as well as other sites. It provides historical background and important data on clean-up processes and goes on to offer critical reviews of 14 published protocols for evaluating natural attenuation.

This book evaluates the risks to human health and the environment posed by exposure to methyl tertiary-butyl ether (MTBE). Used almost exclusively as a fuel additive, MTBE is blended with gasoline to provide both octane enhancement and an increase in oxygen content. MTBE currently numbers among the 50 chemicals produced in the highest volume worldwide. Production and use are expected to increase, particularly in countries where oxygenated or reformulated gasolines are required in national programs aimed at reducing ambient air levels of carbon monoxide and ozone or benzene and other volatile hydrocarbons. A summary of sources of human and environmental exposure is followed by an assessment of what is known about the chemical's environmental behavior and fate. Studies demonstrate that, after discharge into air, MTBE largely remains in the air, with smaller amounts entering soil and water. Although atmospheric MTBE can partition into rain, data indicate that atmospheric transformation by hydroxyl radicals is a more important pathway of removal.