Europe is considering tightening air quality standards following the latest analysis of the impact of air pollution on people’s health, it emerged yesterday.

Janez Potočnik, the European environment commissioner, signalled that the bar to combat poor air quality could be raised further as he prepares his decision on whether to grant the UK government an extension on meeting an existing directive on dangerous airborne particles, known as PM10s.

He said the “serious question” now being considered was whether these agreed standards should be strengthened because of new analysis provided by the World Health Organisation.

The minute particles are emitted by traffic and from factories and could cause heart attacks, strokes, asthma and lung diseases.

The UK remains in breach of the limits for PM10s, which came into effect at the end of 2004, because of hotspots in London, prompting a second and final written warning from the European Commission last year to clean up or be taken to the European court of justice where it could be fined up to £300m.

Boris Johnson, London’s mayor, revealed last year that pollution causes more than 4,300 premature deaths a year in London at an annual cost of up to £2bn.

The last Labour government reapplied for a time extension, until June 2011, to comply; the decision is due in the next few weeks. Potočnik said yesterday, before meeting with the environment secretary, Caroline Spelman, that the commission was still considering that submission. The government insists it can deliver.

Potočnik said that 20 of the 27 EU member states had infringements because they were “overshooting” on the standards that had been previously agreed.

He said that if the UK fails, the next step would be the court. “We would do that if we were pretty much convinced we could win that kind of case in the court,” he said.