Pollution from Motor Vehicles and Its Control.

The motor vehicles in the world have a large amount of pollution rate. The harmful gases coming out from the engine or the exhaust or the fuel tank are harmful to the environment. These gases or pollutants can be controlled by some systems. In this article, I will discuss the topic “Pollution from Motor Vehicles and Its Control”.


Pollution from Motor Vehicles and Its Control

Vehicular emissions contain the following pollutants :

  1. Carbon monoxide.
  2. Unburnt hydrocarbons.
  3. Oxides of nitrogen.
  4. Lead oxides.
  5. Sulfur.
  6. Smoke.

Of these pollutants, carbon monoxide is the most undesirable. The effects of carbon monoxide inhalation are headaches, sickness, or loss of mental alertness. Carbon monoxide reacts with hemoglobin (Hb) in the blood to give carboxyhemoglobin(COHb).  Because of the formation of carboxyhemoglobin not only is the Hb unavailable for oxygen transport but also the dissociation of oxygen from the other Hb molecules is shifted to a slower rate.

A combination of strong sunshine and stagnant air allows unburnt hydrocarbons and oxides nitrogen to combine chemically to produce “photochemical smog”. Smog causes damage to rubber, clothing paints, and exposed surfaces. Ozone present in the smog can cause cross-linkage of molecules, mutations, and apparent premature aging. Peroxy acetyl nitrate(PAN) present in photo-chemo cal smogs makes eyes water. Certain polycyclic hydrocarbons like benzo (a) pyrene and benzo (e) pyrene are also harmful.

Lead, present as Lead oxides in the automobile exhaust can be harmful particularly for children in the age group I to 5 years. Sulfur dioxide causes visibility attenuation. It is also a phytotoxicant. Increased mortality due to bronchitis and lung cancer is also caused by dioxide.

There are four sources from which pollutants are emitted into the atmosphere in a vehicle. These are:

  1. Crankcase. From the crankcase, hydrocarbons are emitted. This constitutes 20 percent of hydrocarbon emissions from a vehicle.
  2. Tailpipe of the exhaust system. All pollutants namely carbon monoxide, Hydrocarbons, oxides of nitrogen, and Lead oxides are emitted from the exhaust.
  3. Carburettor. From the carburetor, only hydrocarbons are emitted.
  4. Fuel Tank. Due to evaporation, hydrocarbons escape into the atmosphere in vapor from the fuel tank.

Read More- Diesel Smoke Problem in India | Read the Full Article. 

Control of Pollution from Motor Vehicles

There is an urgent need to limit the emission of carbon monoxide, unburnt hydrocarbons, and oxides of Nitrogen by legislation in the interest of public health. Similarly, there is no need to limit the smoke density of the emissions from automobiles by laying down limits.

Once limits are laid down by legislation, the same will have to be enforced. To enforce the standards laid down, we need measurement instruments and measurement techniques.

Emission standards for smoke from diesel vehicles and Carbon monoxide from petrol vehicles have already been laid down by the Indian Standards Institutions. Under these standards, for vehicles operating in urban areas, the smoke density shall not exceed 65 Hartrid ge Smoke units (as measured by free acceleration method) or 5.2 Bosch or 75 Hartridge Smoke units (as measured by full load method).

In non-urban areas, the limits laid down are 70 Hartridge units (free acceleration method) or 5.5 Bosch or 80 1lartidge units (full load method) respectively. Carbon monoxide shall not exceed 3 percent by volume of exhaust gases during idling.

In the case of vehicles, which are over 5 years old or which have run over 80,000 km, the carbon monoxide emission shall not exceed 4.5 percent by volume of the total exhaust.

Emission standards for other pollutants have still not been laid down in our country. Similarly, noise pollution standards have also not been laid down as yet in our country.

Noise pollutes the environment as surely as chemical waste or smoke and th us demands equal attention. There is considerable evidence that prolonged noise exposure may be both physiologically and psychologically harmful.

Noise causes annoyance, difficulty in speech/communication, degradation of task performance, interference with sleep, and generation of stress. For measuring traffic noise, the “A” weighted decibel is the appropriate unit dB (A). A standard of 60 dB (A) for daytime noise level (L 50) due to traffic may be suitable for our country. As already standard has as yet been laid down.

Smoke density can be measured by an instrument called a Smoke meter. The two Smoke meters used throughout the world are the Hartridge Smoke meter and the Bosch Smoke meter. The Indian Institute of Petroleum, Dehradun, has developed a simpler smoke meter, which is suitable for checking black diesel smoke and is to be used in conjunction with an Evaluation chart.

The Indian Standards Institution has laid down a measurement procedure for measuring Carbon monoxide in their IS:5182 (Part X)-1977 (Methods for measurement of air pollution: Part X carbon monoxide). Today more sophisticated exhaust gas analysers are available.

The principal instrument in current use is the rapid response non-dispersive infrared gas analyzer (NDIR). This instri•ment will need to be ‘installed in Air Pollution laboratories and vehicle manufacturing units. It is not suitable for the use of Enforcement Staff on the roads.

Crankcase emissions can be minimized by providing positive crankcase ventilation(Positive Ventilation System). Emission from the exhaust can be controlled by a combination of methods:

  1. Exhaust gas re-circulation for control of the oxide of Nitrogen.
  2. Catalytic or non-catalytic conversion of hydrocarbons.
  3. Oxidation of carbon monoxide and unburnt hydrocarbons in the exhaust system by low-pressure air injection into the exhaust.
  4. Engine modification to reduce the volume of contaminants released from the cylinders.

The emission of fuel vapor from the carburetor and fuel tank may be reduced by installing fuel vapor recovery systems. For example. an Evaporative Loss Control  Device (ELCO) has been developed by ESSO.

Regarding all the above-mentioned control devices, it will be necessary to initiate a dialogue with the prominent vehicle manufacturers in the country before deciding on the appropriate regulations. Because the petrol engine is so important to the general economy, legislation on pollution cannot be so rigorous as to force it out of use. While it is clear that any source of pollution should be reduced as much as practicable. We can only act as far as a combination of economic factors and the common good a low.

The standards laid down by the Indian Standards Institution in respect of smoke density and carbon monoxide emission level can be accepted and incorporated by amending Rule 159. A further provision will have to be added under Rule 159 to empower officers of the Motor Vehicles Department and Police Department to direct the drivers/owners of vehicles to undergo tests to determine the smoke level and level of other pollutants emitted by the vehicle.

Read More- Crankcase Ventilation | What does a Crankcase Ventilation do?

Emission Standards For Pollution Control

Emission standards are the standards set by the governments to control the air pollution. The vehicle manufacturer has to make sure that their vehicles do not cause pollution more than the standards specified if the vehicle is run with good quality fuel and a properly maintained engine.

The government of India introduced certain legislative measures for emission control from automobiles, such as the Air Prevention and Control of Pollution Act-1981, Environment Protection Act-1986, and Motor Vehicles Act-1988. The notification of National Ambient Air Quality Standards and vehicle emission norms such as Bharat-I, and Bharat-II on the model of Euro-I and Euro-II, provide a benchmark for regulatory authorities like the central and state pollution control boards.

Bharat-I was introduced for petrol vehicles in 1991, and for diesel vehicles in 1992. In the year 2000 passenger cars and commercial vehicles will be meeting Euro-I equivalent India 2000 norms while two-wheelers will be meeting one of the tightest emission norms in the world. Bharat-IT no1ms equivalent to Euro-IT are in force from 200 I in 4 metros of Delhi, Mumbai, Chennai, and Kolkata.

Euro-I and Euro-II are the international emission standards as given by the European Research Organization. These standards have to be followed by the vehicle manufacturers so that their vehicles do not cause over-pollution. A comparison of Euro -I, II, and III norms is below in Table

Exhaust Emission


Euro-I  Euro-II Euro-III
(Effective from 1.7.92 in Europe) (Effective from 1.9.96 in Europe) (Europe from 1999 onwards in Europe)
(Effective from 1.1.99 to 31.3.2000 in India) (Effective from 1.4.2000 in India) (Effective from 1.1.2005 in India 1.50)
CO 3.16 2.20 for petrol

1.00 for disel


HC+NOx 1.13 0.5-1.0 for petrol

0.7-0.9 for diesel


S 0.02% 0.003%
Suspended particles 0.08-0.01 0.025
Total Smoke 3.38 1.70

Conclusion on Pollution from Motor Vehicles and Its Control

Efforts to control pollution from motor vehicles require a multi-faceted approach involving government regulations, technological advancements, public awareness, and individual behavior changes. It is crucial to address this issue comprehensively to protect both human health and the environment.

Frequently Asked Questions(FAQ’S)

How does motor vehicle pollution affect human health?

Exposure to pollutants from motor vehicles can lead to respiratory and cardiovascular problems, aggravate existing health conditions, and pose risks to vulnerable populations, such as children and the elderly.

How do emission standards work in controlling motor vehicle pollution?

Emission standards are regulations that set limits on the amount of pollutants vehicles are allowed to emit. Manufacturers must comply with these standards, leading to the development and use of cleaner vehicle technologies.

Are electric vehicles a solution to motor vehicle pollution?

Electric vehicles (EVs) are considered a cleaner alternative as they produce zero tailpipe emissions. The promotion of EVs, along with advancements in battery technology, contributes to reducing the environmental impact of motorized transportation.


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