It’s shameful that our government had to be dragged through the courts twice by ‘Client Earth’ to make it plan to achieve an air quality standard for nitrogen dioxide (NO2) that it should have met by 2010.

Air quality is estimated to cost £20 billion in damage to health and £2.6 billion in loss of productivity each year.

Ill-health effects implicated include cancer, asthma, stroke, dementia and poor development of children’s lungs.

The main air quality pollutants from vehicles now are NO2 and micro-particles known as PM10 and PM2.5.

Diesels have always been heavy polluters and since 2000 the EU has rightly instituted ever tighter tests for new cars to meet but the manufacturers designed engines which passed the tests but were much more polluting on the road.

The Government was right to encourage diesels because they produce less climate-changing carbon dioxide than petrol vehicles but wrong to trust the manufacturers to reduce the real-world NO2 in line with the standards.

I don’t know whether the manufacturers or the regulators were more at fault, but we now have a lot of dirty diesels on the roads.

It’s not enough for Reading’s streets to meet the standard for NO2 - it’s not a ‘safe’ level and says nothing about the presence of other pollutants.

We urgently need Clean Air Zones in the affected areas by 2018 to ban the dirtiest diesels and charge other diesels entry.

In parallel there should be a diesel scrappage scheme funded by the manufacturers, a new Clean Air Act covering all pollutants, and transport policies to encourage cleaner vehicles, public transport, and cycling and walking.

John Booth, Earley