Question to the Department for Environment, Food and Rural Affairs:

To ask the Secretary of State for Environment, Food and Rural Affairs, what proportion of nitrogen dioxide pollution in the UK is caused by emissions from private cars.

We assess emissions in terms of nitrogen oxides (NO_x) rather than nitrogen dioxide (NO₂) because the proportion of NO₂ varies significantly across vehicle types. Passenger cars (including both petrol and diesel vehicles) contribute 29% of the total emissions of NO_x in the UK. Passenger cars contribute 45% of NO_X emissions from road transport.