Currently there are several European countries in a similar situation so it is not just the UK at fault. Much of it is being blamed on diesel cars, now nearly 40% of the 30.3 million cars on British roads, and there have been discussions on various fiscal and taxation approaches to dealing with this. These include grants towards electric cars, scrappage schemes to encourage drivers to move to newer, more efficient vehicles and taxes or even bans on older diesels in cities.
It is true that diesel cars emit more nitrogen dioxide than their petrol equivalents and they have higher particulate emissions, especially from older vehicles. But this has to be balanced against lower overall fuel consumption, lower unburnt hydrocarbons and longer engine life (saving energy on the manufacturing of replacement cars). Petrol engines are also far less efficient on short runs so this is an added factor.
Electric cars look enticing with the 'zero emission' badge but the electricity has to be produced somehow and unless it is from photovoltaics, hydroelectricity, wind-turbines or nuclear (raising other questions) there are still going to be emissions: much of the electricity in the UK comes from coal-fired power stations, and despite the efforts to reduce the pollution from these plants, they can never be 100% clean and they will always produce carbon dioxide.
In fact the most efficient cars are small-engined diesel ones, especially when the energy loses from power generation, transmission and battery charging are built in to the measurement of electric car efficiency. Hybrids come close but they tend to be heavier and more complex. In recent years there has also been progress with petrol engine designs, leading to smaller turbo-charged units fitted with comprehensive electronic engine-management-systems.
But a simple way to reduce pollution is to make more of our journeys using public transport. Buses do generally run on diesel fuel but it is easier to make several hundred-thousand buses low-emission rather than over 30 million cars. Electric trains are commonplace, not hampered by inefficient batteries and some cities have also introduced tram systems. It's much more effective to move 50 people in one vehicle than have 50 cars with single occupants.
Then again, if we really want to tackle vehicle pollution, and obesity while we are at it, how about redesigning UK towns and cities to make them better places for walking and cycling? Rather than cleaning up cars we can rid ourselves of them and walk into town, to the bus stop or to the railway station.
That really would make a difference.