Defra has warned people to be braced for “very high” levels of air pollution between Wednesday and Friday.
The Department for Environment, Food and Rural Affairs (DEFRA) has explained that the elevated pollution levels have been caused by a combination of light south-easterly winds, the continental air flow and dust which has blown up from the Sahara desert.
The Defra forecast added: “The current elevated pollution levels over parts of the UK are caused by light winds allowing the build-up of pollution, plus dust from the Sahara contributing to pollution levels.”
People with heart and lung conditions have been warned to avoid strenuous activity.
A Defra spokesperson said: “The high level of air pollution this week is due to a combination of local emissions, light winds, pollution from the continent and dust blown over from the Sahara.
“We want to keep improving air quality and have introduced a new five-day forecast service in addition to investing heavily in local and transport initiatives to tackle this issue head-on.”