I think that the right hon. Gentleman has started his speech already. The figure I can give him is that in the hotspots in our inner cities, some 60% of the nitric oxide comes from transport. It is quite difficult to break that down and say how much comes from buses, taxies, lorries, delivery vans and cars, but there is no doubt that tackling the private car, particularly in those spots, will help to make a real difference in reducing NOx emissions. Transport is a particular issue, as is the older diesel engine. We cannot ignore what is going on; we need to take action.
Motorists were encouraged to switch to diesel through changes to the vehicle taxation system. We now know that that was a policy mistake. The uptake of diesel cars rocketed. The proportion of diesel vehicles on British roads increased from 20% in 2005 to 37.8% in 2015. That was a deliberate Government policy. Between 2005 and 2015, we did see cleaner diesel vehicles, but naturally they still give off particulates and NOx.
In turn, the number of extra diesel vehicles has caused a host of air quality problems. Diesel engines emit a higher level of nitrogen oxides. Those gases cause or worsen health conditions such as asthma and bronchitis and even increase the risk of heart attacks and strokes. They are linked to tens of thousands of premature deaths in Britain every year.
As a result, the Select Committee on Environment, Food and Rural Affairs, which I chair, branded poor air quality a “public health emergency” in our recent report to the Government. Four in 10 local authorities breached legal nitrogen dioxide limits last year. That shocking statistic shows the scale of the problem.