The impact of the gasoline additive methyl tertiary-butyl ether (MTBE) on groundwater: a German perspective

Methyl tertiary-butyl ether (MTBE) has been introduced into gasoline for the purposes of octane enhancement and oxygenation. As an octane booster, it replaced lead-based compounds in the USA and Europe, from the late 1970s on. Use as the preferred fuel oxygenate at concentrations of 10 to 15% (by volume) in "cleaner burning gasoline" brought a major increase in MTBE demand in the USA during the 1990s. In Europe, MTBE contents in gasoline vary between about 0.2 and 14% (by volume), depending on country and grade, but are expected to rise as new EU regulations require the reduction of octane-enhancing aromatics. MTBE can enter groundwater from either point sources or non-point sources. The occurrence of MTBE in groundwater and surface water has raised great concern in the USA, where the oxygenate is now intensively monitored for. Monitoring for MTBE in European countries has been very limited and publications are scarce. Our own studies in Germany indicate that MTBE is present at considerable concentrations in groundwater in the vicinity of gasoline contaminated sites (up to 80 mg l(-1)). We believe that assessment of the possible risks of MTBE use in Germany and other European countries is impossible without having sufficient actual data. It is necessary to start monitoring programmes with regard to MTBE contamination.