Flawed, but accepted

Flawed, but accepted

A recent study by the Central Pollution Control Board has exonerated vehicles of being the worst polluters in Delhi and Mumbai. Instead, it has pinned down liquefied petroleum gas (LPG) as the biggest source of fine pollutants. Experts have contested the study, saying the findings are unsubstantiated and scientifically untenable. The study will set the basis for the post-2010 emissions standards for vehicles and fuels.

The board (CPCB) had asked premier institutes IIT Madras, IIT Kanpur, National Environmental Engineering Research Institute (NEERI) in Nagpur, The Energy and Research Institute in Delhi, and the Automotive Research Association of India in Pune to conduct the study in Delhi, Mumbai, Pune, Kanpur, Chennai and Bengaluru. Researchers analysed the load of major air pollutants like PM10 and PM2.5 (particulate matters less than 10 and 2.5 micrometres), oxides of nitrogen (NO_x) and sulphur dioxide (SO₂), identified their sources and suggested action plans to achieve clean air.

It is the NEERI study analysing sources of PM2.5 in Delhi and Mumbai that has come under fire. These fine pollutants cause diseases like lung cancer. They are mostly emitted by vehicles. But NEERI’s study claims LPG combustion is the biggest contributor to PM2.5 load in Delhi’s air; it contributes 61 per cent in industrial areas, 49 per cent in residential areas and 41 per cent along roadside.

Sarath Guttikunda, developer of SIM-air, an air quality monitoring tool used at the Commonwealth Games in Delhi, questioned the figures. Fine particulates are not emitted directly from LPG combustion. Besides, how can the results be logically possible given the number of diesel-fuelled trucks that pass through the city every day, the use of gensets and the number of industries in the region, he said. CPCB studies in Chennai, Bengaluru, Kanpur and Pune show vehicular exhaust as the biggest contributor of PM2.5 pollutants.

Apart from being dubious, NEERI’s report was also incomplete. “We pulled back the findings on PM2.5 in Mumbai as they were erratic,” Rakesh Kumar, head of NEERI Mumbai, said. It was based on limited samples, he added. Prashant Gargava, scientist at CPCB, said the conclusions for PM2.5 in the final report are “preliminary” and further research should be done to ascertain the contribution of point sources.

PM2.5 is an emerging pollutant and researchers were asked to analyse its sources at a later stage of the study. Hence, the samples were limited, he added. Kumar said CPCB should have mentioned in its final report that PM2.5 data was based on limited studies.

The report will set the basis for the post-2010 emissions standards for vehicles and fuels

It is not clear how the report passed the technical scrutiny and peer review process of the Union environment ministry despite such discrepancies, said Anumita Roychowdhury, executive director of the Centre for Science and Environment, a Delhi non-profit.

The industry has already turned the NEERI study to its own advantage. At two recent public seminars, the Society of Indian Automobile Manufacturers and the Indian Oil Corporation Limited cited NEERI’s findings to establish that vehicles are not major contributors of pollution and that diesel vehicles pollute even less. Several studies have shown that diesel cars emit 2.5 times more particulate matter than petrol cars.

The study, however, clinched enough evidence to call for urgent and aggressive actions to curb tailpipe emissions. It notes vehicles are responsible for NO_x load in air by 45 to 94 per cent. When inhaled, NO_x aggravates heart diseases. It shows vehicles contributed 41 per cent and 22 per cent of the total PM10 load in Bengaluru and Kanpur. PM10 causes respiratory diseases.

The study recommends progressive introduction of emission standard Bharat Stage IV from this year onwards and tighten it further from 2015. The standards should be fully implemented by 2017. It also recommends that electric vehicles should be at least 2 per cent of the city fleet, all commercial three- and four-wheelers should be fuelled by natural gas and public transport should be promoted to achieve the clean air.

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