Those with lung and heart conditions should avoid strenuous activity outdoors while people suffering symptoms of pollution - including sore eyes, coughs and sore throats - should cut down the amount they do outside, health experts said. Asthmatics might need to use their blue reliever inhalers more often as they could be prone to attacks.
The warnings came after parts of England experienced the highest level of air pollution recorded. The high pollution levels, which are set to spread into south-west Scotland, have been caused by a combination of light south-easterly winds, the continental air flow and dust blown up from the Sahara desert.
Dr Keith Prowse, honorary medical adviser to the British Lung Foundation, said: "Heavy air pollution of the kind we're seeing in places across the UK can have a significant impact on people with pre-existing respiratory conditions, such as chronic obstructive pulmonary disease and asthma, worsening symptoms such as breathlessness."