"The EPCA in a report in 2012 has stated that benefits of CNG transition are not visible due to growth in diesel vehicles, because diesel vehicles are known to emit higher smoke particles and Nitrogen Oxides than petrol cars," Environment Minister Jayanthi Natarajan said during Question Hour.
Earlier in 2007, the EPCA had expressed this concern in a detailed report filed by it in the Supreme Court titled "Controlling Pollution from the growing number of diesel cars in Delhi".
"In the report, EPCA had recommended to the Court that there is a need to ban the use of diesel in cars in Delhi," the minister said.
The Central Pollution Control Board had carried out a study in 2007 in six cities - Bangalore, Chennai, Delhi, Kanpur, Mumbai and Pune.
"As per the studies, the ambient air quality data of these cities in respect of Particulate Matter revealed that contribution due to all vehicles is ranging from 2 per cent to 48 per cent," Natarajan said.
Government is taking several steps to control pollution caused by vehicles.
These include implementation of Bharat Stage-IV emission standards for all category vehicles, reducing sulphur content in petrol and diesel, implementing pollution under control norms, promoting use of alternative fuels like CNG, electric vehicles, bio-diesel; building more by-passes to avoid unnecessary entry into the city, and strengthening mass transport system.