This study draws two key conclusions:

• "Widespread MTBE contamination on the same scale as in the USA (especially California) is unlikely. The risk of groundwater contamination is unlikely to increase, given important differences between the USA and the EU, although robust enforcement of the existing Member State regulatory framework is required to ensure this risk remains low in the future."

• "Adequate enforcement of Member State requirements for the construction and operation of UST systems is the key to safeguarding water quality in the EU".