Responding to the landmark judgement of the National Green Tribunal against diesel vehicles more than 10 years old, VivekChattopadhyaya, the programme manager of the Air Pollution Control Unit of the Centre for Science and Environment, New Delhi, pointed out that the pre-2005 diesel vehicles were causing 7.5 times higher pollution than petrol cars.

Thus, one diesel car is equivalent to 7.5 petrol cars when it comes to pollution. New studies in Europe indicated that the particulate matter pollution load caused by the diesel cars were at least 27 times higher than petrol cars regarding Particulate Matter (PM) emission, he said.

UNEP study

A United Nations Environment Programme (UNEP) document on ‘Developing diesel pollution, reduction strategies for cities,’ pointed out that diesel combustion was a significant source of harmful pollutants that were damaging to human health in urban areas.

“While diesel engines are more efficient than gasoline engines, they are a disproportionate contributor to exposure of people to fine particulate matter (PM), the pollutant of primary concern in Asia and in the majority of Latin American cities,” it said.

The document pointed out that the “diesel emissions are complex, containing fine particulate matter, toxic organics, and harmful gases including precursors for secondary particulate and acid rain formation. A key air quality concern in developing countries is the health impact of fine and ultra-fine particulate matter,” it said.

The PM “emitted by diesel engines is very small, predominantly sub-micron in size, which is the size fraction considered most damaging to health. These particles have hundreds of toxic chemicals adsorbed onto their surfaces, including many known or suspected mutagens and carcinogens leading to cancer, pulmonary and cardiovascular diseases,” it said.

“Diesel emissions, and their corresponding health effects, are higher in developing countries than in industrial countries due to poor or lack of vehicle maintenance, improper vehicle repair, use of older vehicle technology, low fuel quality, fuel adulteration, lack of monitoring and enforcement of standards, and poor institutional capacity for coordination of policies across sectors that affect diesel emissions,” the document noted.

Mr. Chattopadhyaya pointed out that the diesel-fired Multi Utility Vehicles (MUV) were considered more polluting than their smaller cousins. While one MUV would emit 0.68-gram nitrogen oxide /kilometre, it would be 0.28g/km in a pre-2005 diesel car.

The diesel MUV emits two times higher nitrogen oxide than a diesel car. In case of PM emissions, a diesel MUV emits three times higher PM compared to a diesel car.

“It’s also the case with the release of suspended particulate matter, and MUVs are the major pollutants,” he said.

“Pre-2005 diesel vehicles are causing 7.5 times higher pollution than petrol cars”