§ Mr. Matthew Taylor
To ask the Secretary of State for the Environment, Transport and the Regions what research his Department has(a) commissioned and (b) evaluated on the impact of reducing the sulphur content of petrol and diesel on vehicle emissions of pollutants. 
§ Ms Glenda Jackson
The Department has not commissioned any research specifically aimed at determining the impact of the sulphur content of fuel on vehicle emissions since a number of studies have been carried out by a range of organisations that already enable assessments to be made. A comprehensive study was carried out by the European automotive and oil industries as an element of the Auto-Oil study undertaken by the European Commission. This has lead to proposals for170W tighter fuel quality and vehicle emissions standards to come into effect from the year 2000. The studies show that sulphur can have an adverse effect on vehicle pollutants arising primarily through its detrimental effect on catalyst efficiency. For petrol vehicles fitted with catalytic convertors reductions in CO, HC and NOx can be achieved when using reduced sulphur fuels. For diesel vehicles, reduced sulphur fuel can lead to a reduction in particulate emissions, but the effect is enhanced in vehicles fitted with catalysts by reducing sulphate formation within the catalyst.