The Hindu : New Delhi News : Delhi's air quality improving

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Friday, Dec 22, 2006
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Delhi's air quality improving

Staff Reporter

But gains lost due to rising number of cars: Study by `Resources for the Future'

NEW DELHI: There is some mixed news for the Capital on the air front. While the good news is that air quality in the city is better, according to a study conducted by Washington DC-based think tank "Resources for the Future", mostly due to introduction of compressed natural gas (CNG), the gains made are being lost with many more cars hitting the roads.

Looking at the air quality of the city, the study has analysed the levels of pollution over a 15-year period and seeks to answer what has led to these changes. The results of the study were released at a press conference at the Centre for Science and Environment office here on Thursday.

"Of all the interventions made to clean up Delhi's air, conversion of diesel-run buses into CNG mode has been the most important. The CNG's programme has made a huge difference to air quality. The results suggest that the conversion of buses to CNG has helped reduce carbon monoxide and sulphur dioxide. The study did not suggest that CNG has contributed to the increase of nitrogen dioxide," said Urvashi Narain who conducted the study along with her colleague Alan Krupnick.

With the levels of carbon monoxide and sulphur dioxide on the decrease in the Capital, it seems that there has been an increase in nitrogen dioxide, which is a worrying sign. The other major contributor to a health hazard, respiratory suspended particulate matter seems to have stabilised.

The study attributes the rise in nitrogen dioxide in the air to increase in the number of diesel-run cars and light trucks. The change from two-stroke to four-stroke engines in two-wheelers is also contributing to the increase in this pollutant.

"The conversion of buses to CNG is important because they travel more kilometres in the city and contribute more to the pollution load. But irrespective of the fuel type, the increase in the number of cars on the roads and the number of kilometres travelled by all fuel type, is leading to an increase in nitrogen dioxide,'' she pointed out.

CNG may be declared "guilt free" for an increase in the levels of nitrogen dioxide, but there is an urgent need for the Capital to put a limit to the number of vehicles on the roads. And apart from the avoiding overcrowding of roads, there is also a need to re-look at the technology used in auto-rickshaws.

"The CNG-switching gain, which is apparent in the case of buses, is not seen in auto-rickshaws. This is possible because of the poor technology and needs to be investigated. There is also a need to put in place stricter emission standards for diesel cars.''

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