The deadly diesel deception: We were bullied into buying diesel cars to help fight global warming. Now experts say this 'green' fuel is killing thousands of us

A motorist filling his van with diesel. Increasingly it seems that we have all been conned (file picture)

Many years ago we upgraded our car for a larger diesel model. Three children, along with pushchairs, travel cots and child seats meant we no longer fitted inside a 'family' car and we ended up with a people carrier.

Our first-ever diesel was a tank. It handled like a bad-tempered elephant, smelt like a dirty chip shop and rattled like a pneumatic drill.

But despite the noise and sluggish performance, we believed the sacrifice was worth it because it was a greener car, emitting less of the global-warming gas carbon dioxide than petrol models, and was kinder to the environment and our wallets.

We weren't alone. Thanks to clever marketing, a dramatic improvement in the performance of diesel engines, and tax breaks from a succession of governments obsessed with reducing carbon dioxide emissions, Britain has experienced an extraordinary 'dash for diesel' over the past 15 years.

Today, half of the two million new cars bought each year in the UK are diesel, compared with just 18 per cent in 2001. There are nine million diesel cars on the road — more than at any time in history — and three million diesel vans.

But increasingly it seems that we have all been conned.

Pollution

For now that the Government has successfully persuaded us to invest in diesel, it has emerged that the fuel is not only less efficient than we were led to believe, but dirtier and more damaging to the environment than petrol. So much so, in fact, that it is killing us in our tens of thousands.

This week, Professor Frank Kelly, chairman of the Department of Health's committee on air pollution, said diesel engines could be responsible for more than 7,000 deaths a year because of the pollutants they emit. He added that governments had taken the 'wrong route' for decades by encouraging drivers to switch from petrol.

It is a view backed up by Martin Williams, professor of air quality at King's College London. 'In hindsight the switch to diesel was a mistake,' he says. 'In the past 20 years we've had far more toxic emissions from cars than we should have done.'

How did such a dirty, noisy and dangerous technology fool so many experts?

The reason appears to be that car makers, governments and environmental groups were so wrapped up in the mania for reducing carbon dioxide emissions that their 'experts' managed to overlook the other highly toxic pollutants that diesel engines produce.

Californian research last year found a link between pollutants in diesel fumes and autism

It is undeniable that diesel engines are around 20 per cent more fuel-efficient than petrol engines, so they generate less carbon dioxide per mile.

That is why governments encouraged everyone to switch over from petrol by using tax incentives. Petrol vehicles with low fuel economy and high carbon dioxide emissions were penalised with a higher road tax, while diesels with low emissions were placed in a lower tax band. Indeed, diesel cars with the lowest carbon dioxide emissions were not subject to road tax at all.

I am no global warming denier. I believe that climate change is taking place and agree that we need to reduce carbon dioxide emissions. But not at any cost.

And the cost of the switch to diesel is terrifying.

Diesel exhaust is a complex mixture of thousands of gases and fine particles that contains more than 40 toxic air contaminants. These include cancer-causing substances such as benzene, arsenic and formaldehyde, as well as other seriously harmful pollutants.

The microscopic particles in diesel exhaust are less than one-fifth the thickness of a human hair, small enough to penetrate deep into the lungs and bloodstream, causing inflammation, asthma attacks, heart attacks and strokes, and worsening lung disease in the elderly and young. The World Health Organisation says long-term exposure to these particles — called PM2.5s because they are just two-and-a-half thousands of a millimetre across — alters the way children's brains grow and could make them less intelligent.

Californian research last year found a link between pollutants in diesel fumes and autism.

Other U.S. studies have shown that adults exposed to PM2.5s suffer a greater loss of mental faculties than those living away from pollution. The exhausts also spew out nitrogen dioxide, a substance that irritates lungs and reduces our ability to fight disease.

For people living near busy roads, the fumes are a constant nightmare.

Dangerous

There have been attempts to clean up diesel. In 2009, new rules meant every diesel car had to fit particulate filters that trap some of the most dangerous particles. Even tougher rules are coming in the next couple of years.

But the benefits of filters have been overstated. In urban driving they work less well and clog up quickly. And even with the tougher European rules, diesel vehicles will remain far more polluting than petrol.

This is why an increasing number of air-quality experts are calling for a switch back to petrol.

The AA points out that the typical driver can save 10 per cent on fuel and carbon emissions without switching to diesel simply by driving more sensibly, pumping up their tyres and sticking to the speed limit.

The consumer association Which? has also shown that the fuel efficiency claimed by manufacturers of diesel vehicles should be taken with a pinch of salt. When it tested the official EU laboratory-based fuel efficiency figures against the reality of running a car on Britain's roads, the differences were staggering.

Ford claimed that its diesel Ford Fiesta managed 76mpg on a mix of urban and main roads. Which? showed the real figure was 63mpg. The Vauxhall Astra diesel was supposed to do 69mpg. Which? said the actual figure was 13mpg lower.

Again and again, the published figures — particularly for diesels — were too optimistic.

'The quoted figures you see in adverts are based on a European test cycle which all vehicles have to go through,' explains Professor Williams. 'But it's based on driving a car on rollers, not on the road. You don't get the accelerations and decelerations of the real world and they are not realistic.'

The Which? probe unearthed another dirty diesel secret.

It's well known that diesels are typically £2,000 dearer in the showroom, while the fuel costs around 7p per litre more than petrol.

Critical

In the long run, however, they are supposed to save you money, particularly if you use them for long journeys. But Which? found the benefits didn't always outweigh the costs.

For example, the owners of a new Astra who do an average mix of urban and main-road driving would need to keep it for nine years or drive it 100,000 miles before recouping the extra costs. For a Ford Fiesta the figure was eight years.

On top of all this, it has now been discovered that diesel cars could contribute very much more to global warming than scientists first thought. The tiny particles of soot — or 'black carbon' — in diesel exhaust are now believed to be second only to carbon dioxide in their ability to cause global warming.

Sadly, when it comes to the environment, politicians and pundits often lose any grip on their critical faculties. They blindly support the latest supposed panacea for our ills — then force us to adopt it, with often grotesque consequences.