Got a cough? Can't laugh it off? Living in Australian cities can be a real pain in the respiratory system. The air alone can kill you - and that's official.

As motor vehicle accident death rates continue their downward trend and little is done to reduce carcinogenic emissions, it is only a matter of time until more people die from vehicle emissions than from road traffic accidents.

While 1995 was a bad year on Australian roads with 2029 deaths (623 in New South Wales), the NSW Health and Air Quality Research Program estimates that more than 400 people in that state died from particle pollution - and one third of those are attributed to vehicle emissions, primarily from dirty diesels.

Vehicle emissions are responsible for a range of respiratory illnesses and deaths and in Victoria the EPA estimates a 60 percent increase in lifetime cancer incidence caused by particulate emissions in the 15 years to 2005.

With no effective restrictions on vehicle exhausts - trucks are allowed to blow thick black carcinogenic smoke in Australians' faces at will - there is little likelihood of improvement. Politicians and officials talk about "realities" of the motor industry's influence and defend themselves by claiming the need of the States and Territories to move in concert on emission levels. But officials of the National Road Transport Commission and the National Environment Protection Council quite clearly state that they are setting national minimum standards and not maximum standards.

Diesel vehicles do not have to blow any smoke at all, let alone the black clouds that they are currently allowed. "Cleaner diesel" - fuel with less than 0.05 percent sulphur content is mandatory in the European Union (Australia has a 0.5 percent sulphur content maximum) and when Scandinavia introduced tough emissions controls, low sulphur diesel soared from one percent of market share to 75 percent of market share in 18 months. The oil companies in Europe, like in Australia, claimed at the time that it wasn't possible to develop the fuel, and then met the demand. But simple routine maintenance is sufficient to dramatically reduce black smoke.

Pollution isn't just poor visibility - respiratory diseases kill. In 1994, 250 Victorians died from asthma (825 Australia wide) and 13 percent of asthma hospital admissions are related to high ozone levels. Asthma allergens such as pollen have been show to adhere to sticky diesel particulates.

Tough action has been taken on the causes of vehicle accidents - speed restrictions, random breath testing and seat belt legislation - but little has been done to curb vehicle emissions. Along with the ozone-asthma and particulate-cancer links, carbon monoxide emissions have an adverse effect on people with heart disease and oxides of nitrogen, volatile organic compounds, benzene, 1,3-butadiene, formaldehyde, poly aromatic hydrocarbons and asbestos are all vehicle emissions that contribute to diseases in humans and animals.

While the data is far from complete - some liken the relationship to the days before the tobacco-cancer link was proven - the road pollution toll is probably as high as the road accident toll or not far from it. And our air quality is expected to worsen.

Victorian EPA documents show that Melbourne has the worst ozone levels in Australia, far worse than London and Toronto. That our ozone levels are lower than Los Angeles, Bangkok and Hong Kong isn't saying much. Melbourne regularly breaks both the Victorian 120 parts per billion "acceptable" and the 150ppb "detrimental" levels for ozone. The World Health Organisation says 76ppb is the level for concern for human health.

A direct causal relationship between transport emissions and asthma has not been proved, but Melbourne is also the top rating capital for deaths by asthma. In five of the 10 years to 1994, Melbourne had Australia's greatest rate of asthma death and has consistently had a higher death rate than the other seven capitals, excepting Sydney.

While the National Asthma Campaign concentrates on specific asthma allergens like house dust mite droppings, Monash University senior lecturer in Epidemiology and Preventive Medicine, Dr Michael Abramson, says the evidence is building that transport emissions are significantly responsible for respiratory illness.

"About 13 percent of hospital admissions from asthma can be attributed to high ozone levels. Motor vehicles, especially diesels, emit particulates and PM10 and they have been shown to be associated with death and respiratory illness in overseas studies," Dr Abramson said. University of New South Wales' Professor Adrian Bauman says air quality is a factor in triggering asthma symptoms, but is a more obvious factor in other respiratory illnesses.

About 1.4 million Australians have asthma, including one in five children under the age of 12. Asthma killed 825 people in 1994. The medical cost of asthma to Australia is about $320 million with a further $400 million lost in work productivity. The cost of respiratory illnesses directly related to transport emissions is unknown, but nearly 10,000 people - including cigarette smokers - died from respiratory diseases in 1994.

The cost of improving Australian air quality needs to be compared to the cost of illness to the community, but that is unlikely as long as the deaths are not as obvious as a car accident. Hold your breath.