THE fact that we have a World Environment Day, is telling on the deep reaching impact of pollution in our lives.

Of all the types of environmental pollution, the one that is most visible in our day-to-day lives is the pollution caused by vehicular emissions. Millions of tonnes of particulate matter and poisonous exhaust gases are released into the air every day by the vehicles that we use.

Vehicular emissions have been the bane of many Indian cities, where thick smog and acid rain have not just wrecked havoc on the infrastructure, but have also severely affected the health of the city's residents. Thankfully, today, we can safely say that the worst level of vehicular air pollution is behind us.

Rising public awareness about the ill effects of vehicular pollution, increase in corporate responsibility amongst automobile companies and the timely intervention of the courts ensured that legislation governing the formulation of emission standards was put in place.

The involvement of the country's apex court also ensured that a road map for future emission standards was drawn and legislation did not end with just stipulating the current norms.

Much has been achieved in the field of controlling vehicular emissions. The emission reduction achieved from pre-1989 levels is over 85 per cent for petrol driven vehicles and over 61 per cent for diesel vehicles from 1991 levels. And yet, since India embarked on a formal emission control regime only in 1991, there is a gap in comparison with technologies available in the US or Europe. At present, we are trailing mature automobile markets such as the US, Japan and Western Europe in terms of the equivalent Euro norms in force in these countries.

In India, it was only in 1991 that the first stage emission norms came into force for petrol vehicles and in 1992 for diesel vehicles. From April 1995, new laws were effected mandating the fitment of catalytic converters in new petrol passenger cars sold in the four metros of Delhi, Calcutta, Mumbai and Chennai, along with the supply of unleaded petrol.

Availability of unleaded petrol was further extended to 42 major cities later and now Euro II grade unleaded fuel is available throughout the country.

Emission standards were further raised in the year 2000 when passenger cars and commercial vehicles had to meet the Euro I equivalent - India 2000 norms, while two-wheelers were also similarly made to meet tighter emission norms. At present, the emission norms stipulated for two-wheelers in India is the most stringent in the world.

Euro II equivalent Bharat Stage II norms have been in force from 2001. After instituting Bharat Stage II emission norms, the next milestone in the vehicular emissions roadmap was the introduction of the more stringent Bharat Stage III (BS III) norms for passenger vehicles, which is in turn based on the relevant Euro III standards.

The aggressive implementation of emission norms has already led to a visible improvement in air quality in cities such as Delhi and Mumbai. The new BS III norms will take the process one step forward with the coming into force of the standard for all new vehicle registrations after April 1, 2005.

The new emission standard will be mandated in about 11 cities initially, which will include the National Capital Region of Delhi, Mumbai, Chennai, Kolkata, Bangalore, Hyderabad, Ahmedabad, Pune, Surat, Kanpur and Agra.

The Government late last year notified the new Bharat Stage III norms and automobile manufacturers have managed to meet the standard only because oil companies have simultaneously improved fuel quality. Improvements in fuel quality included a reduction of sulphur content and an increase in octane levels for the two fuels diesel and petrol.

Vehicles that run on traditional fuels such as petrol and diesel produce highly toxic oxides of sulphur and nitrogen, in addition to carbon monoxide and hydrocarbons.

In the case of diesel, a large portion of the exhaust fumes also includes soot and suspended particulate matter. The emission standards that are being formulated progressively reduce the maximum allowable limits of these elements in the exhaust emission.

As a result, the BS III norms will lead to a near 50 per cent reduction in emission of hydrocarbons and nitrogen oxide. In all, new BS III petrol cars will be emitting about 28 per cent lower emission than the current Bharat Stage II cars and 89 per cent lower exhaust gases than cars manufactured in 1991.

Similarly, there will be a reduction in emission of about 30 per cent in new diesel BS III cars compared to BS II cars and that will also be about 72 per cent lower than diesel cars produced in 1992.

Upgrading the existing fleet of cars in order that they are BS III compliant has needed new technology inputs in the form of new components to treat exhaust emissions and to improve fuel injection efficiency.

Some of the changes that petrol engines have been put through include new, more powerful electronic control systems for the fuel injectors, changes to the exhaust systems, including new generation catalytic converters, upgradation of sensors, reduction of evaporative emissions and in the case of diesel driven vehicles, it has included adopting new generation common rail direct injection (CRDI) type engines and exhaust gas recycling mechanisms.

Leading the front by providing new technologies for lowering emissions are companies such as MICO-Bosch and Delphi, which have introduced the latest common rail diesel injection systems in India.

Vehicle population is growing at the rate of over 12 per cent per annum and today the number of vehicles plying on Indian roads is approximately 44 million. The vehicle mix is also unique to India in that there is a very high proportion of two-wheelers (over 75 per cent).

With such a rapid rate of growth in vehicular population and with such a diverse mix of vehicles, the future of emissions control hinges on the adoption of an integrated approach where improvement in vehicular technology and fuel quality are simultaneously effected. Further, the Government has to supplement emission control legislation with a systematic programme for inspection and maintenance of in-use vehicles and better traffic management in the major cities of the country.

At present, while legislation to control emissions have been successfully implemented and compliance is ensured, there is very little monitoring of the weak system of inspection and maintenance of in-use vehicles presently in place. This is a very important issue that needs to be addressed since at any point in time new vehicles only constitute about seven to eight per cent of the total vehicular population.

The country's road infrastructure needs to be improved and a more widespread, forceful inspection of in-use vehicles is required for making the current emission control efforts more effective.

The Government could also consider legislation stipulating the maximum number of years of usage for public transport vehicles and mandate replacement of vehicles to ensure lower emissions.

Thanks to stringent emission standards and the adoption of other measures such as the switch over to alternative fuels such as compressed natural gas (CNG) for public transport vehicles in cities like Delhi, air pollution is down dramatically in the major metros. And yet, unless the tempo is kept up with new, tighter norms and better monitoring, the sheer volume of vehicles that is being added each year to Indian roads will smoke out the Industry's and Government's efforts at containing vehicular pollution.