Gone in a puff of smoke

Then there's the old favourite: that more lung cancer cases are caused by air pollution and diesel fumes than by smoking.

This belief was fuelled by a caravan of travelling scientific stooges who were brought out on speaking tours by the tobacco industry in the 1970s. They did a fine job because today one in four smokers agrees that air pollution is a bigger killer than tobacco.

The problem with this belief is that the highest rates of lung cancer are found in the remotest parts of the country with the freshest air, not in city suburbs adjacent to factories.

Why? Because smoking rates are highest in the bush.

The second category of excuses are "bullet-proof" beliefs. These rationalise that while smoking is harmful to most people, they are somehow "bullet-proof": that they have protective genes (14 per cent of smokers); that they don't smoke often enough to harm themselves (19 per cent); that scientists will have found a cure for cancer by the time they are old (16 per cent); that exercise and a good diet will help them avoid smoking-related risks (almost 33 per cent).

Sorry, guys, but scientists have been looking in vain for that magic cancer bullet for 50 years. Then there's the small problem of heart disease, which kills more smokers than cancer.

Those who bank on having "good genes" rather than those that make them susceptible to cancer face the same problem smoking causes multiple diseases, with lung and other cancers, heart disease, and chronic obstructive lung disease being the most prevalent. The combination of multiple susceptibility genes and multiple diseases means that all smokers will have at least one susceptibility gene for one or more smoking-related diseases.

So if you win on the cancer swings, you may well lose on the heart disease roundabout.

The third category of excuses are known as "life's a jungle" beliefs. This lumps smoking risks in with all the other dangers of life. An amazing 41 per cent of smokers take comfort in the idea that "everything causes cancer these days", while 56 per cent agree that "it's dangerous to walk across the street', and 46 per cent believe "smoking is no more risky than lots of other things that people do".

In this way, news of the latest reports on smoking scares can be blithely dismissed as just more confirmation that life's a jungle. And you can't go through life worrying about all these risks that doctors go on about, right?

So just how dangerous is smoking compared to walking across the road?

Most of us cross at least one road each day. In the year to July 2004, 246 pedestrians were killed in Australia. In a population of 20 million, that means each of us has a one in 81,300 chance of being killed as a pedestrian each year.