Air pollution reaches high levels in parts of England
2 April 2014 Last updated at 17:13 BST
People shopping in Chelmsford, Essex were experiencing the effects of air pollution which reached high levels in parts of England on Wednesday.
The pollution - a mix of local and European emissions and dust from the Sahara - hit parts of south England, the Midlands and East Anglia.
Defra warned people with health problems to avoid strenuous activity and outside exercise.