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A welcome, if overdue,  admission  of the dangers of diesel particulates - but where is the reference to the damage done by public transport?  The centres of cities like Edinburgh are jammed packed with un-filtered buses, belching diesel fumes while stuck in traffic congestion caused by 'road calming'. Outside the rush hour they are often under utilised. Add in diesel powered commuter trains, delivery lorries and chelsea tractors on the daily school run and it no wonder that pollution monitoring is sounding alarms.

9,000 UK deaths a year caused by diesel fuel

By RICHARD GRAY. 13.08.2006

Particles that lead to heart attacks are the lethal price of economic motoring
(but what about buses?)


The combination of economy and performance has won the hearts of millions of motorists. But Scottish scientists have uncovered disturbing new evidence that diesel engines are causing thousands of deaths each year.

Researchers have identified tiny soot particles from diesel exhausts - 30 times smaller than the width of a human hair - as the chief culprits in 9,000 fatal heart attacks in the UK annually.

The Edinburgh University team has worked out how the soot particles cross from the lungs into the blood stream, where they cause arteries to harden and clots to form. The findings are the hardest evidence yet of the deadly side-effects of diesel exhausts and will increase the pressure on manufacturers to fit engines with filters as standard.

Scotland on Sunday can reveal that proposed new European rules will compel car makers to fit filters to diesel engines from 2008, but even if the law is passed, the most dangerous particles will probably still escape into the environment.

The number of diesel-engine cars on the roads in the UK has increased dramatically from 1.6 million to more than five million since 1994.

Researchers at Edinburgh's Queen's Medical Research Institute have identified exhaust particles called PM2.5s as the most damaging to the human body. The miniscule soot fragments are caused by incomplete burning of fuel. While petrol engines create PM2.5s, diesel generates vastly higher quantities because it is a heavier fuel.

Professor Ken Donaldson, a toxicologist who helped lead the research team, said: "These particles are so small they pass quite easily through face masks that people often wear to protect themselves from traffic fumes.

"Ironically drivers themselves might be most at risk if they are stuck in traffic, as the exhaust fumes from the car in front are drawn directly into their own cars."

The researchers, funded by the British Heart Foundation, identified the particles using a series of experiments that tested the vascular response of volunteers to air with traces of different pollutants.

They discovered that while microscopic particles found in the air in unpolluted areas, from substances such as sea salt and soil dust, did not cause any response, those from diesel exhausts caused a rise in artery damage.

The scientists believe highly reactive metals and chemical groups in the diesel soot particles interfere with the normal function of blood vessels, reducing their ability to relax effectively, a process that eventually leads to them hardening and thickening.

The levels of exposure pedestrians might expect to encounter while walking along a busy city street were also found to reduce the amount of anti-clotting proteins in the blood by a third.

Heart attacks are most commonly caused by clotting in the main arteries after they have become narrowed or partially blocked by fatty deposits.

It is thought the particles use up nitric acid in the blood which normally helps to prevent blood vessels from constricting and produces anti-clotting proteins.

Dr David Newby, the lead cardiologist on the project, said: "Compared to other risk factors such as cholesterol, high blood pressure and smoking, the role these particles play is less important, but on top of these other things it can be quite significant. The difference is that the whole population is exposed to them unlike these other factors that affect individuals. Air pollution affects everybody as they don't have a choice."

Surging oil prices have seen the popularity of diesel cars rise over the past few years as they are more economical than models that run on unleaded petrol

Last year, diesel cars accounted for more than 35% of total sales compared with just 14% five years ago.

Under the European Commission's EURO5 standards, it is hoped filters fitted to diesel engines will slash particulate emissions by 80%. If approved, the directive will come into force in 2008. Some car manufacturers are already offering optional filters for diesel engines.

But experts and environment campaigners claim that under the European limits requiring particle emissions to be cut in weight, the lightweight PM2.5s could still be emitted in high numbers without breaching the regulations.

The Edinburgh scientists now plan to test commercially available diesel engine filters for their ability to remove these dangerous particles.

Duncan McLaren, chief executive of Friends of the Earth Scotland, said: "It now looks as if proposed anti-pollution legislation will not reflect the latest scientific discoveries about the true health impact of particulate pollution.

"The problem is not helped by the fact that in Europe vehicle manufacturers continue to lobby to have measures designed to protect health watered down even further."

But the car industry last night insisted that it was already taking steps to cut particles released by diesel engines.

Carlo Cucchi, from the European Automobile Manufacturers Association, said that total particle emissions from diesel cars had dropped by 82% since 1992.

He said: "The removal of the PM2.5 particles emitted by diesel engines will be achieved with the introduction of Diesel Particle Filters, a technology today ready for mass production."

See also

Great Smog of 1952
Doing without oil
Energy gap - an essay on options
What energy?
Cities of the future