After strongly backing the Euro-I and Euro--II auto norms, environmentalists are now gunning for the diesel fuel saying that engines powered by it produce significant amounts of Respirable Suspended Particulate Matter (RSPM), the main culprit behind health-related problems. Pending a final decision on the ban on diesel vehicles, the Centre for Science and Environment (CSE), has sought for a restriction on the number of diesel cars. The Supreme court has also fixed the number of fresh registrations at 250.