We all notice the smelly, black diesel fumes pumped out by big, dirty vehicles. But cars and lorries emit other air pollutants that we cannot see or smell and which may cause us harm.

Two of the worst pollutants derived from vehicle emissions are nitrogen dioxide (NO2) and particulate matter (PM10). They're responsible for the poor air quality and smog in cities like York. And they also lead to breathing problems and cardiovascular disease.

Although air pollution can affect us all, it is young children and the elderly who are most at risk. Asthma sufferers are also sensitive to poor air quality and attacks can be triggered by raised levels of common air pollutants. As well as producing immediate symptoms with severe ill effects, air pollutants can result in long term effects or premature death. In fact, a Government survey revealed that up to 24,000 people die prematurely each year because of air pollution.

However, vehicle emissions aren't the only way transport can affect our health. Our increased reliance on our cars as a way of getting around has dramatically changed our lifestyles as these facts show:

- 25 per cent of all car journeys in Britain are under two miles - that's only a 30-minute walk or a 12 minute bike ride- Heart disease rates would drop by 5-10 per cent if one third of all short car journeys were made by bike- Almost a third of children who live within a 15 minute walk of school are driven- Road traffic is the largest external cause of noise in housesSo why not leave your car at home for a day and rediscover the benefits of a bit of fresh air and exercise?