MTBE was originally added to unleaded fuels to meet octane requirements. It is now mainly used to improve fuel efficiency, thereby reducing vehicle emissions, or to reduce the use of regulated substances such as benzene.
Though human health risks are low, the substance makes water taste foul at very low concentrations. In the USA, where it has been used for longer and in greater quantities than in Europe, it is being blamed for widespread groundwater contamination. Denmark, which depends almost entirely on groundwater for drinking water supplies, recently called for an EU ban on MTBE in fuel (ENDS Daily 9 November).
The agency considers Anglo-Welsh drinking water to be relatively well protected because MTBE usage is low by EU standards and because only 30% of drinking water comes from groundwater - although that figures rises to 70% for the densely-populated south east of England. According to the report, there has so far been only one case of drinking water contamination in England and Wales.
However, the report stresses that MTBE usage is expected to increase when stricter EU controls on the sulphur and aromatic content of fuels take effect in 2005 under the 1998 fuel quality directive. It warns that contamination of private wells could increase significantly if MTBE concentrations reach 5%.
In anticipation of this trend, the agency recommends annual monitoring, leak prevention measures at petrol stations near drinking water sources and a national or European study into underground petrol storage tanks. A European Commission official told ENDS Daily that plans were afoot at EU level to investigate the environmental implications of greater MTBE use.
Anglo-Welsh environment agency, tel: +44 14 54 62 44 00. The report is entitled "A review of current MTBE usage and occurrence in groundwater in England and Wales".
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