§ Ms Walley
To ask the Secretary of State for the Environment, Transport and the Regions what the recommended limit is of methyl tertiary butyl ether (ug/L) in drinking water, and what monitoring the Drinking Water Inspectorate has made of drinking water supplies to detect methyl tertiary butyl ether. 
§ Mr. Mullin
There is no standard for methyl tertiary butyl ether (MTBE) in drinking water. MTBE is detected in drinking water by its odour/taste at concentrations 435W much lower than concentrations that would be a risk to health. Because MTBE has the potential to contaminate groundwater sources used for drinking water supply, the Drinking Water Inspectorate has checked the monitoring for MTBE carried out by water companies. Apart from one site specific incident in 1990 which resulted in the water company treating water to remove MTBE, this monitoring has not revealed a problem. The water companies are aware of the potential problems and remain vigilant. The Inspectorate is liaising with the Environment Agency on MTBE.