The city council wants to declare all of Oxford an Air Quality Management Area (AQMA) because European targets for clean air aren’t likely to be met.

The AQMA would see the county council, as the highways authority, coming up with special anti-pollution measures. Such measures can only be good news for cyclists, as well as anyone in the city who likes breathing.

What is ‘dirty’ air? A century ago, the air in cities was a viscous murk of coal smoke. The Great Smog of 1952 led to the Clean Air At (1956), which dramatically reduced levels of sulphur dioxide.

By the 1980s, the watchword was particulates, found in vehicle exhaust fumes. These tiny pieces of matter suspended in the air are associated with asthma, lung cancer and premature death. Lead was linked to problems such as lowered IQs and schizophrenia, and was phased out from the early 1990s.

In the past ten years, CO2 has taken over the debate about emissions. CO2 is harmless to us in small quantities. But, in spite of the prevalence of catalytic converters that remove some particulates, vehicles still emit a lethal cocktail, including nitrous dioxide.

Nitrous dioxide is a toxic reddish-brown gas with a sharp smell. Not to be confused with innocuous nitrous oxide (laughing gas), nitrous dioxide causes lung disease and is therefore is no laughing matter.

By far the biggest source of nitrous dioxide in the UK is traffic fumes. And levels of nitrous dioxide are a third higher in the St Clements area than in the city centre.

I’m not a bit surprised. With the exception of the buses heaving up and down High Street, the city centre is fairly traffic free. It’s in the queues around the Plain, Cowley Road, Abingdon Road, Frideswide Square, and so on, and where air pollution is at its worst.

The thing about air pollution is that you can’t really see it. Driving is perceived by most as a reasonable and blameless way of getting about. Certainly, few feel guilty about it.

Last week I wrote that governments should mix a harmless coloured dye into fuel to make all exhaust fumes visible to the naked eye. Perhaps it’s time that drivers DO feel bad about driving: if everyone could see the invisible poisons that engines are pumping into the atmosphere, perhaps they, and passers-by, might feel differently about the blamelessness of driving.

Tens of thousands of people in Oxford and the county’s market towns choose to drive. This free choice has serious but unseen effects on the air, and begs the question: whose choice matters? Those who drive, or everyone? For everyone has to breathe. Drink driving was made unpopular not only by the force of law but also by social stigma. It is now time that unnecessary car journeys were viewed as antisocial and unacceptable – because what difference does it make whether you are killed by a drink driver or a sober driver whose exhaust you have no choice but to inhale?

Thousands of travellers to and in Oxford have been persuaded to abandon their car in favour of the bus. With air pollution getting worse, it’s now time to persuade drivers that they can cycle or walk to work and to school instead of fumigating everyone. It is time that the council recognised that most people are capable of cycling five miles on urban journeys.

Come on, get us on our bikes!