London's cars the most polluting in the country - but should cyclists be worried?

London is home to the country’s least fuel-efficient and polluting cars, a study has found.

The average car in the capital gives out out 176.95 grams of carbon dioxide per kilometre – equivalent to around 40mpg.

By contrast, in Peterborough, the greenest city according to DVLA data, cars do 50 mpg and emit 142.03g/km.

In towns including St Albans and Brighton, Cambridge and Chelmsford, pollution levels have breached EU safety limits.

It’s bad news for cyclists in these cities who risk their health through breathing toxic fumes, as vehicle emissions in the worst ten cities are far in excess of the 128.3g/km average for new cars sold last year, according to figures from the Society of Motor Manufacturers and Traders.

However it’s even worse news for drivers. As we reported earlier this year, the most polluted part of the street is not on the pavements where pollution monitors are positioned, or at the road edges where cyclists ride. Instead, it's, inside cars themselves, according to a study.

Researchers at King’s College London used five MPs from the Government's Environmental Audit Committee (EAC) as guinea pigs in a study of London air pollution.

The MPs were set up with devices that measured airborne pollution and used GPS to record the location.

“Travelling in vehicles gave the greatest average exposure,” said Dr Ben Barratt, a senior air quality scientist at King’s who oversaw the research. “Among the worst was when the MPs got a taxi across London.”

The monitors measured the amount of microscopic carbon particles - produced largely by diesel engines - that the MPs inhaled. Inside taxis, they were found to have inhaled up to 50 million particles per breath.

Walking around Whitehall and Oxford Street, they inhaled 6-7 million particles per breath. At their destination, London's City Hall, levels fell to 3 million particles per breath.

As we recently reported, diesel vehicles are a major source of air pollution. The UK is  facing fines of up to £300 million per year from the European Commission for its failure to rein in emissions of nitrogen dioxide from diesels.

Governments were supposed to have reduced air pollution to “safe levels” by 2010. A five-year extension was granted to countries with problem areas, as long as they had “a credible and workable plan for meeting air-quality standards within five years of the original deadline” but Britain looks unlikely to hit the target in 2015.

According to a Confused.com OnePoll survey of 2,000 adults that found more than a third – 36 per cent - have no idea what their vehicle emits in CO2.

Despite that, more than half (52 per cent) consider it important to reduce emissions, although a third (33 per cent) cannot afford to buy a low emission car.

According to Confused.com, Department of Health figures estimate that 28,416 deaths in Great Britain in 2010 were attributable to particulate air pollution – largely from diesel vehicle exhaust emissions – including 3,389 in London alone.

“That ranks pollution as a far bigger killer than traffic accidents,' it said.

“To put it into context, Department for Transport figures state that there were 1,713 road deaths in all of Great Britain in 2013.

“It is estimated that, depending on the area, between 6 per cent and 9 per cent of deaths in London are caused by airborne man-made particles.”