A boon or a bane ? : After the traffic police, it is now the turn of enviromentalists and pollutin control officials to worry about the slash in car prices. The number of cars on city roads will increase, therby magnifying the air pollution problem, they fear. Environment ministry officials expect the number of cars in Delhi to virtually double in a few years, a cause for concern because vehicles are responsible for 70 per cent of the city's air pollution.