One of them, Iqbal Malik contends that using lead-free fuel in vehicles not equipped with catalytic converters will result in the emission of poisonous gases like benzene. All the four public sector oil companies - Indian Oil Corporation, Bharat Petroleum Corporation, Hindustan Petroleum Corporation and Indo Burma Petroleum have from September 1 onwards arranged for all gas stations in the city stock only unleaded petrol. ``We want to ensure that a major lethal substance (lead) is out of the air," insists Dilip Biswas, chairman, Central Pollution Control Board (CPCB).

Malik however maintains that the pollution due to lead has not been totally eliminated as its content is still more than the international level. ``The lead content in the unleaded petrol now available is .013 per cent, still 2.5 times higher than the accepted international level, which is .005 per cent,'' she says. Malik also charges that the introduction of unleaded petrol has in a way affected the efficiency of cars. ``Out of the 500 Ambasssadors, 250 Fiats and 200 Standard Gazelles we surveyed, 95 per cent had problems using unleaded petrol,'' she says, adding that it usually causes `knocking' in old cars. The Maruti cars surveyed, however, had no problem with the new petrol, she noted.

Besides, a vehicle without a catalytic converter emanates fumes toxic in nature which increase the benzene content in the atmosphere, she says. ``With benzene content still remaining at five per cent as it was earlier, the transition to unleaded petrol, even though a well-thought of move, is still half-baked," she charges.