Overview of Methyl Tertiary Butyl Ether (MTBE) Detections in Public Drinking Water Supplies in the United States

Abstract

We provide a review and summary of methyl tertiary butyl ether (MTBE) water monitoring data that have been collected as part of national, multi-state, and state-wide assessments in the United States. Specifically, we summarize the key attributes of 24 publicly available studies or data sets and characterize the detection frequency and detected concentrations of MTBE for different water types based on these studies. The original sampling data from each study were obtained and independently analyzed wherever possible. For each study, the detection frequency of MTBE was calculated assuming any concentration above the reporting or analytical limit of detection and at three different concentrations (1, 5, and 20 μg/L). Detected concentrations of MTBE were based on all reported drinking water samples and were computed using summary statistics such as the median, mean, range, and distribution percentiles. The primary focus of this assessment is on MTBE detections in public drinking water served by groundwater or surface water, although several published studies also contain sampling data from domestic (private) drinking water wells. Some non-drinking water data sets (e.g., sampling data from ambient groundwater) are also included because it was not always possible to identify or separate these data by water type due to the manner in which they were coded or reported. These latter studies therefore contain some sampling data that are not informative for assessing MTBE drinking water exposures to consumers.

Keywords:

• MTBE
• oxygenate
• groundwater
• drinking water

Acknowledgement

We thank Ken Unice and Jeffrey Knutsen for their assistance reviewing and analyzing the MTBE drinking water data sets. This work was partially funded by Exxon Mobil while the authors were employed at ChemRisk Inc. with the remaining work completed by the authors without any financial assistance.

Notes

¹Note that the oxygen content requirement for reformulated gasoline in the Clean Air Act Amendments (Sect. 211(k)) was eliminated by the Energy Policy Act of 2005 (Sect. 1504).

^a Source: USEPA 2006: Reformulated Gasoline: Where You Live. Available at http://www.epa.gov/otaq/rfg/whereyoulive.htm (accessed November 20, 2006).

^b Source: Delta Environmental Consultants, Inc. 2005. Groundwater Oxygenate Cleanup Levels for LUST Sites. Available at http://www.epa.gov/OUST/mtbe/oxytable.pdf (accessed November 20, 2006).

^c Source: USEPA 2006. State Actions Banning MTBE (Statewide). Personal communication dated February 2006 received from Kurt Gusfasson October 3, 2006.

^d Source: Energy Information Administration 2006. Motor Gasoline Outlook and State MTBE Bans. Available at http://www.eia.doe.gov/emeu/steo/pub/special/mtbeban.html (accessed on November 20, 2006).

^e Other oxygenates include methanol, isopropanol, n-propanol, n-butonal, sec-butanol, tert-butanol, tert-pentalol (tert-amylalcohol), etheyl tert butyl ether (ETBE), disapropyl ether (DIPE), tert butyl alcohol (TBA), iso-butanol, tertamylmethylene ether (TAME).

²Michael J. Moran is a hydrologist for the United States Geological Survey who has analyzed and interpreted groundwater quality data for the National Water-Quality Assessment (NAWQA) program.

∗Raw data obtained and analyzed.

∗Raw data obtained and analyzed.

∗Raw data obtained and analyzed.

∗Raw data obtained and analyzed.

§> 99% of the non-detect samples reported a detection limit within this range.

†Appear twice within the table in both Public and Private Drinking Water Sections.