Did you, like me, assume that a low CO2 car was a clean car?

We have been encouraged by the company car tax system as well as manufacturer advertising to believe that a car that pumps just 100g of carbon dioxide every kilometre is cleaner than one that pumps out 150g/km.

It is true that a low-CO2 car is going to bring global warming on a little slower.

But other than on our wallets – with lower tax and less visits to the filling station – there is no immediate impact of driving a low CO2 car.

However, this focus on CO2 has diverted our attention away from other tailpipe emissions. And this was brought home in a quite disturbing presentation last week.

At the top of the Gherkin overlooking London – where air quality is getting worse – a presentation detailing the true story of tailpipe emissions and what they do to our health and that of our children was given.

There were a variety of speakers: one from Volvo, one from Environmental Protection UK and one – and by far the most disturbing – from professor Frank Kelly of King’s College London.

He told us that 50,000 people will die this year from respiratory illnesses caused by poor air quality.

If we are lucky and do not succumb to a killer disease brought on by the polluted air we breath, we will still die younger – everyone’s average age expectancy is now down by eight months because of pollutants we breath in.

This polluted air is not just caused by transport emissions, but they are a major factor.

Particulates, which are pumped out only by diesel engines, sit in children’s lungs causing them to under-develop and leaving them prone to respiratory disease.

Just to illustrate the point, we were shown what was essentially a snapshot of a boy’s lung polluted by ultrafine diesel particulates.

Euro 6 will help, but the particulates in this child’s lung were tiny – far smaller than the pollutants that Europe is legislating against.

Then there are the nitrogen oxide emissions (NOx). These can cause cancer as well as create ozone.

The horror story continues.

But the most startling – and worrying – fact from the night was that our focus on CO2, while important, does not give us the true picture of how clean a car really is.

For example, a petrol 2.5-litre Volvo V70 manual estate emits 201mg/km of non-CO2 pollutants while a 1.4-litre Fiat 500 Start Stop, counter intuitively, pumps out 484mg/km or more than twice as much.

So if you do actually care about the environment we all live in, when it comes to choosing your next company car take some time to discover its total emissions and not just those that will save you in BiK.