Diesel engines may power most of the vans, trains and cars that transport thousands of commuters in the United Kingdom everyday but experts blame diesel engine pollution for thousands of early death in the UK per year.

Department of Health's committee on air pollution chairman Frank Kelly said that with 2008 figures showing that 29,000 die early from air pollution annually, fumes from diesel engines may be responsible for about one in four air pollution-related deaths which translates to over 7,000 deaths per year.

The government has urged drivers to switch from petrol to diesel since the 1970s because the latter was believed to release lesser greenhouse gases, which are known to trap heat in the atmosphere and contribute to the greenhouse effect and global warming.

Because diesel-powered cars emit lesser carbon dioxide, people are also encouraged to switch to diesel because of tax incentives. As a result, diesel is now used by over half of all registered cars in the UK.

Scientists, however, learned that diesel generates more nitrogen oxides and toxic particles that cause unwanted effects on health. The toxic particles from diesel, for instance, pass through the lungs and then enter other organs in the body which raises risks of stroke, heart attack and asthma problems. Fumes generated by diesel-powered cars also harm the brains of young children raising their risks for schizophrenia and autism.

Catalytic converters, which convert toxic exhaust gas pollutants to less to toxic pollutants, have greatly improved in petrol-powered cars but not as much in diesel cars until lately.

"Clearly they do emit a lot more particulate matter from their exhausts than the petrol equivalent," Kelly said. "And ... one of the technological advances has actually been the exhaust system generating nitrogen dioxide to burn the particulates off."

Kelly, who is also a professor of environmental health at King's College London, said that diesel cars that are five years old and older should be banned in the cities.

Jonathan Grigg, from the Queen Mary University of London, pointed out that diesel pollutants can affect the cognitive function in children and that kids are particularly vulnerable to risks associated with air pollution.

"Long-term exposure to air pollution suppresses lung function and leads to vulnerability through life," Grigg said. "It's a major concern. We are setting up children to sub optimal conditions in later life."