Air pollution - the 'invisible hazard' of the air on our streets
The revelation that Volkswagen used software in some of its cars to cheat emissions tests has prompted the European Commission to pressure car makers to agree to bigger reductions in diesel car emissions.
Government figures suggest fine particles from air pollution generally contribute to 29,000 deaths a year in the UK.
Nitrogen dioxide, a gas found in diesel fumes, is linked to 23,500 deaths a year.
Fergus Walsh examines the threat to public health.