In the West, air pollution monitoring authorities measure the concentration and size of the particles those with a diameter of 10 microns or less, or PM 10, and those of 2.5 microns or less, or PM 2.5 ( see chart ). In March 98, the Central Pollution Control Board ( CPCB ) shifted to these measures and came out with startling findings the level in Delhi is five to six times higher than normal. Says Roychowdhury: "About 90 per cent of the total PM in diesel emissions is of one micron size which is not only toxic but dangerously carcinogenic too." But the diesel lobby feels the fuel is being unfairly singled out. Says an official from a major diesel car maker: "Yes, theres air pollution; but when policy planners discuss ways of bringing the situation under control, they invariably focus on automobiles, diesel cars in particular. Ironically, according to CPCB s own surveys, 81 per cent of Delhis SPM and toxic load comes from manufacturing industries and power plants. The transport sector accounts for only 10 per cent. Instead of checking industrial pollution, theyre trying to take the easy way out by axing diesel." Automotive engineering consultant A. S. Subramanium agrees. "There is no conclusive medical evidence to suggest that diesel exhaust is carcinogenic. And out-side Delhi, petrol contains lead which is known medically to damage the brain and kidneys apart from clogging respiratory organs. Its a paradox really. Also, no one is pointing out that the two- stroke engine, with a mixed lubrication system, is one of the major sources of particulate matter." Says Dr B.S. Murthy, a retired IIT professor who has conducted extensive research on the issue: "In Europe, the diesel engine is being used increasingly for its thermodynamic fuel efficiency. And in Europe, diesel has no price edge as in India or Brazil. Companies there are making large investments in developing sophisticated, low emission diesel engines. Peugeot- Citroen is launching a new car fitted with a particulate trap that reduces particulate matter emission by 100 per cent." Another reason, say experts, for turning to diesel is high CO2 emissions from a petrol engine. Todays typical petrol engines emit 245 gm per km, while the emission for a standard diesel engine is 157 gm. This, set against a backdrop of Euro emission norms of 140gm/ km by 2008 and 120 gm/ km by 2012, has compelled conversion to diesel. But, according to CSE , most countries, like the US, UK, Japan, France and Australia, have already begun to revert to petrol and are trying to discourage use of diesel. In India, a diesel ban was vital because not only is it at the root of pollution, but its also of extremely poor quality. In August last year, the California Environmental Authority designated diesel as the strongest air pollutant and asked companies to undertake corrective measures. Says Shankar Prasad, advisor, California Air Resources Board, who was in Delhi recently: "If small particulate pollution level in California ever reached the same levels as in Delhi today, the authorities would have declared an emergency, taken all vehicles off the road and shut down all emission sources in the city." Clearly, the debate is set to go into the next millennium even as air pollution keeps claiming more and more lives. In 1991- 92, according to a CSE study, about 7,500 people in Delhi died of air pollution related diseases. In the last two years, this has become over 20,000, even as consumption of petrol rose by 31 per cent and diesel by 69 per cent between 91 and 97. And as the number of car- owners rises, this growth rate can only go north. The Supreme Court has asked the Delhi Government to move its entire bus fleet to CNG by April 2001. A decision on diesel- run taxis is also under consideration. But more concerted efforts to fight air pollution than merely banning a single fuel are necessary to give Indias choked capital a timely breather.