NEW DELHI: While Delhi gets moving on its ambitious plan to restrict the number of passenger vehicles on its roads in a desperate bid to improve its air quality, the move has also sparked a debate on just how much of the problem is caused by the burgeoning vehicular population in the National Capital Region.While recent studies point fingers at vehicular emissions as a key contributor to the high air pollution levels in the city—especially the Particulate Matter 2.5 (PM2.5 levels) —there are others who believe that the focus on passenger vehicles may be excessive.A 2007-10 six city study done through National Environmental Engineering Research Institute ( NEERI ) at the behest of the Central Pollution Control Board ( CPCB ) had made some surprising claims then which have been hotly contested.This study—Air Quality Monitoring, Emissions Inventory& Source Apportionment studies for Delhi— said the high PM 10 levels in Delhi were caused more by dust and industries rather than vehicles.The report said while road dust contributed up to 52% of Delhi’s PM 10 levels, vehicles contributed 6.6% and industry share was 22%. Open burning and other area sources contributed 18%.“One has to separate perception from science and data. The study showed road dust was the biggest contributor to Delhi’s high PM levels. Vehicles are also very visible sources of pollution and hence also a perception about how much they contribute. Our assessments have shown it is mostly heavy duty vehicles like trucks and LCVs that cause more pollution,” an expert associated with the CPCB study told ET on condition of anonymity.CPCB studies have repeatedly said vehicular emissions are to blame for high NOx levels.Centre for Science & Environment had rejected the CPCB report in 2011 questioning the methodology used and its allegedly faulty conclusions. “That is an old study with serious methodological issues. All recent studies point to vehicular pollution as a major sources as also supposedly the latest report by IIT Kanpur . Road dust is in the air and overwhelms with its weight and mass but vehicular emissions is what requires priority action due to proximity of individuals to this source and its direct health impact”, Anumita Roy Chowdhury, Executive Director, Research & Advocacy, CSE told ET.Chowdhury’s views are echoed by many others but limitations of data available are also acknowledged. An Emission Inventory of Air Pollutants for NCR by Pramila Goyal of Centre for Atmospheric Sciences, IIT Delhi, had also noted in her 2014 study: “The largest contributor of air pollutant emissions is found to be vehicles followed by industries, power plants and domestic sources”.