Demand for diesel-powered cars is soaring.

Diesel produces fewer greenhouse gases than unleaded petrol but it is more dangerous to our health. RICHARD BLACKBURN reports on an automotive dilemma.

Demand for diesel-powered cars is soaring. Australians bought more diesel cars in the first four months of this year than they did in the whole of 2005.

Sales this year are up 135 per cent on the same period last year and the latest figures show that almost 20 per cent of new vehicles sold this year are powered by diesel. In 2000, the figure was just 10 per cent.

However, the explosive growth is a double-edged sword.

The good news is that diesel-powered engines are more efficient than their petrol cousins and therefore emit less CO2 - the major contributor to global warming.

The bad news is that emissions from Diesel engines are harmful to your health. That includes the latest generation of so-called “clean” diesels.

The Federal Government’s Green Vehicle Guide, which ranks vehicles on their greenhouse gas and air pollution performance, doesn’t have a single diesel vehicle in its top 50 list of low polluters.

Just one makes the top 150 and there are only five in the top 200 vehicles.

Jon Real, a spokesman for the Federal Department of Transport, which maintains the guide, says diesel cars are marked down because they have a “much more significant health effect”.

He says diesels produce about the same amount of hydrocarbons as petrol but significantly more nitrogen oxides (NOx) - a precursor to smog - and particulate matter.

Air quality experts estimate that diesel engines produce particles at about 20 times the rate of petrol engines and it is those emissions that are bad for your health.

Particulate matter has been linked with thousands of deaths worldwide. Side effects range from cancer to respiratory and cardiovascular diseases. NOx have also been linked to serious health problems, including asthma, respiratory disease, infections and reduced lung function in children.

A recent NSW parliamentary inquiry into air quality found that motor vehicles produce 71 per cent of NOx emissions in Sydney and just under 20 per cent of particle pollution.

Real says particulate matter emissions carry a hefty weighting in the department’s assessment of pollution effects from different vehicles. It’s easy to see why.

The most recent figures from the Bureau of Transport and Regional Economics - for 2000 - put the annual death toll from vehicle exhaust pollution at between 900 and 2000 people - higher than the national road toll. It is also estimated to contribute to between 700 and 2050 asthma attacks in Australia each year.