Following leaks or spills of gasoline into the ground, ether oxygenates are more mobile in groundwater than gasoline-range hydrocarbons (GRH) and the potential to reach a down-gradient drinking water well is thus greater for ether oxygenates than GRH. The risk posed by gasoline ether oxygenates (GEOs) to potable groundwater resources is one of taste and odour rather than human health.

In 1999/2000, the Energy Institute (EI)  and the Environment Agency conducted a collaborative study on the occurrence of GEOs in UK groundwater to assess the risk to potable water resources. The study was initiated following several States in the US banning the use of methyl tertiary butyl ether (MtBE) in gasoline, because of its occurrence in groundwater and the perceived risk to drinking water resources.

The study concluded that MtBE did not pose a widespread risk to potable groundwater resources in the UK and modelling predicted that the risk was unlikely to change in the future, so long as there was not a major increase in MtBE usage.

In accordance with recommendations from the 1999/2000 report this study was repeated in 2007/2008 to monitor the situation and test the predictions. This report contains the findings of the recent study and compares them to those from the original study. Also included is a comparison of occurrence of MtBE in the US.