An Evaluation of Tertiary‐Butyl Alcohol for the Development of a Drinking Water Action Level in Delaware

Abstract

AbstractFor regulators to develop risk‐based screening levels (RBSLs) for a petroleum constituent, a maximum allowable concentration at an exposure point, such as a drinking water action level, must be established. Of particular interest to regulators of leaking underground storage tank (LUST) sites in Delaware is the development of RBSLs for the oxygenated compounds that are added to gasoline to increase octane rating and promote cleaner burning fuel. Whereas methyl‐tertiary butyl ether (MTBE) became the first of the oxygenated compounds to gain regulatory attention in Delaware, tertiary‐butyl alcohol (TBA) is not far behind. TBA has been detected at LUST sites throughout Delaware and in some cases has been detected in private water supplies. However, Delaware does not currently have a drinking water action level, or maximum allowable exposure concentration, on which to base regulatory decisions regarding TBA.Toxicological data is inconclusive in classifying TBA as a carcinogen. However, carcinogenic responses are reported in rat and mice studies at extremely high doses. To address TBA in Delaware's Risk‐Based Corrective Action Program, the Delaware Division of Public Health must calculate drinking water action levels based on the results of the toxicological data. However, the establishment of TBA action levels could have a tremendous impact on the costs associated with investigating and remediating a LUST site. TBA may add $2000 to $5000 per year in analytical costs alone for an average LUST site in Delaware.