The automobile industry has a way of being economical with the truth. Take the recent study by the Automobile Research Association of India (ARAI), which underlines that vehicles using diesel are far cleaner than they used to be. There is no doubt that they are, but the question is: do diesel vehicles pollute more than petrol ones? One could do worse than ask Sonia Gandhi, who recently had to be hospitalised (with newspaper reports alleging that the pollution had done her in) because she was feeling breathless in the national capital, where winter causes inversions and pollutants hover much closer to the ground.

According to the Society of Indian Automobile Association Manufacturers (SIAM), the ARAI study shows that since 2001, diesel technology has improved considerably, with nitrogen dioxide emissions falling by a third which, it claims, is one step better than the situation prevailing in Europe. In much the same way, particulate matter has fallen by eight times between 2001 and 2005. Since the tests were conducted on a diesel Tata Indigo, not a foreign car, SIAM has been quoted in the media as saying, that diesel technology has come of age, and that India's diesel vehicles were meeting the government emission norms by more than 300 per cent.

Even if the emissions per car are lower, if the capital and rest of the country are flooded with cheaper diesel cars, that's bad news for people's health.

 •  Cleaning the air in our cities
 •  Tomorrow citizens, imperiled today
 •  Grey skies over colourful roads

The thorn in the flesh of the automobile manufacturers is the Centre for Science and Environment (CSE) in Delhi which for over a decade has been drawing public attention to how diesel is a dirty fuel. Anumita Roy Chowdhury, Associate Director, who specifically monitors air pollution issues, admits that the industry has made strides in this direction. However, she clarifies: "The [ARAI] study clearly shows that the diesel vehicles are still seven times more polluting than petrol cars." Environmentalists are aware that the tiny particulates lodge in the chest and cause respiratory problems and, on occasion, cancer.

A recent study by SIAM shows that Delhi has 85 cars for every thousand people, which works out to one for every 12 people, which must rank with the proportion in many advanced or middle-income countries. Two years ago, SIAM put the number of diesel cars at just under a third in Delhi, and this is expected to rise to half by 2010. What is more, the annual rate of increase in these cars in the capital was twice that of petrol models. (Registration data for the Tata Indica as far back as the first quarter of 1999 showed that 90 per cent of the demand was for the diesel version, because the fuel is cheaper.) Environmentalists would argue that it is the abysmal lack of public transport which is driving Delhi residents to private motorised transport. Just to get a nation-wide perspective, for the country as a whole, there are only eight cars per thousand people. Thus the capital has the distinction of possessing ten times as many cars as the national average.

The CSE shows that the sulphur content of diesel in India is 350 particles per million (ppm), compared with 15 ppm in the US and 50 ppm in Europe. This puts a totally different spin to SIAM's claims and shows that far from being clean, diesel transportation is very dirty. Of course, as SIAM emphasises, it is meeting the national emission norms, but the problem is that these are too lax and industry should be proactive on this score, particularly a house like the Tatas. For instance, in other sectors, such as funding environmental organisations, the Tata Trusts have always been ahead of other industrial groups even, on occasion-when it has threatened their own interests.

There was an almost exact parallel when it came bottled water and colas. The CSE launched a massive campaign to inform the unsuspecting public that both contained high doses of pesticide. The respective industries - some of them overlapped - claimed that they were well within the norms and that the problem was the "raw material", the water used was contaminated. The CSE clarified at the time that its fight was not with the industries but with the government for not imposing stricter norms.

Diesel buses out, but diesel cars still run

On air pollution, it was only on account of the sustained campaign conducted by the late CSE founder, Anil Agarwal and his colleagues, that through the orders of the Supreme Court, all pubic vehicles - buses, autorickshaws and taxis - in Delhi have been forced to switch to the clean compressed natural gas (CNG) and that has made the capital's air far easier to breathe. In 1996, the CSE published its path-breaking study titled Slow Murder: The deadly story of vehicular pollution in India. No less a person than the Vice President, K R Narayanan released the book, which provoked a national debate.

In 1998, the CSE published data from the Central Pollution Control Board (CPCB) to show that on certain days, the suspended particulate matter (SPM) levels in Delhi were 7.6 times the permissible limit. While there was a conspiracy of silence on the part of automobile and two-wheeler manufacturers, the CSE informed the public how very small particles emitted by diesel vehicles, less than 10 microns in size and referred to as PM¹º particles, could penetrate deep into one's lungs and cause permanent damage. The WHO describes these as particles for which there can be no safe limits.

At the time, PM¹º was not being regularly monitored in Delhi. The CPCB did a quick assessment that year and found that in November, the level was five times higher. A UK study showed that 90 per cent of diesel particles are below 1 micron, which gives an idea of the danger posed by this fuel. Diesel exhaust is coated with carcinogens. In 1998, the California Air Resources Board designated diesel particulates as toxic air contaminants.

The automobile industry fought back fiercely, because the market was about to be taken over by diesel vehicles, particularly by what was then the Tata Electric and Locomotive Co (Telco, now Tata Motors). In 1999, the CSE showed, the sulphur content in Delhi's diesel was 2,500 ppm; the cleanest diesel worldwide at the time was below 50 ppm. To compound matters, the technology of diesel cars was poor. As the CSE noted sarcastically: "Under the emission norms already agreed upon (after much dilution), the 'world-class' automobile industry in India was to meet Euro I standards - already enforced in Europe in 1992 - not before year 2000." In 1999, the CSE produced a monograph on diesel vehicles titled Engines of the devil, which didn't amuse the industry.

The industry produced articles and ads to claim that they were safe and clean. Telco even issued a legal notice to Anil Agarwal and his then Deputy, Sunita Narain, for a Business Standard article where a sub-editor had inadvertently illustrated their argument with a picture of a Tata car model. Tenaciously, the CSE top brass challenged the Tatas to file the suit, but wiser counsel prevailed and the company climbed down and withdrew the notice. The CEO of Mercedes Benz actually went on record in an article in the CSE's fortnightly, Down to Earth, that "it may sound like an exaggeration that our exhaust is cleaner than the surrounding air."

In the Supreme Court committee which was set up to provide technical advice on this issue, Agarwal repeatedly emphasised the threat from diesel vehicles and because the manufacturers were unable or unwilling to advance emissions norms, the committee called for a ban on such vehicles after a cut-off date. The Supreme Court noted that according to this committee, 90% of the vehicular nitrogen oxides and particulate matter consisted of diesel exhaust. It went on to state: "It is estimated that chronic exposure to such toxic air contaminants would lead to 300 additional cases of lung cancer per million…The very life of citizens is at stake."

Ultimately, due to the pressure exerted by the industry, diesel was replaced only in public vehicles in Delhi and its use in private vehicles was not restricted. In the recent Auto Expo 2008, SIAM plans to inform visitors that Indian diesel cars are less polluting than European models, while the CSE argues that SIAM should compare this performance with the US Tier II standards, which are far more stringent.

The automobile industry ought to be concerned about the health of citizens - including the head of the ruling party! - rather than make such self-serving claims on behalf of itself.

Buses and cars: not enough space for both on Indian roads

There is no question that despite the conversion of public vehicles to CNG - Delhi is the first such city in the entire world to switch over in this manner - the air of Delhi is far from being breathable and the toll this is taking of health and life itself, even though invisible, is deadly. Even if the emissions per car are lower, if the capital and rest of the country are flooded with cheaper diesel cars, that's bad news for people's health.

In its study of vehicle densities in the country, SIAM has also tried to argue for increasing the number of public buses (this does match it's commercial interests: many automobile manufacturers also make buses) using data to show that Indian cities are by no means densely populated by pubic vehicles. Kochi topped the list as the city with the most extensive public road transport, with nine buses per thousand residents, followed by Jaipur, Chennai and Ahmedabad. Delhi, with 15 million, had only two per thousand population. But the fact that they should be run on natural gas is nowhere mentioned. Or, for that matter, that the obvious corollary is to restrict the private cars on the road, which alone will improve the functioning of buses.

Mumbai's BEST, possibly still the best fleet in the country, is now witnessing a decline in passengers for this very reason. No one who wants to make an appointment can take a bus these days. With the burgeoning number of cars on the roads in future, and with diesel car purchases continuing unchecked, the situation can only get from bad to worse.