Air pollution risk to patients with weak hearts
10 July 2013 Last updated at 07:47 BST
People with weak hearts are being harmed - and in some cases killed - by air pollution, an international study has revealed.
The British Heart Foundation, which funded The Lancet work, says the UK must clean up its air. Many British cities often exceed safe levels set by the European Union.
The government has already admitted that in 15 regions air quality will breach EU limits until 2020, but Defra says it is committed to improving air quality.
Sophie Hutchinson reports.