Londoners should be braced for “very high” levels of air pollution today, the government has said.
Millions of vulnerable people have been warned to stay indoors, as levels of harmful pollutants have already hit the top of the 10 point scale devised by the Department for Environment, Food and Rural Affairs (Defra).
The high level of smog, which is a mixture of local and European emissions combined with dust from the Sahara, is expected to worsen tonight and into Thursday.
Advice on the Defra website says: “Adults and children with lung problems, and adults with heart problems, should reduce strenuous physical exertion, particularly outdoors, and particularly if they experience symptoms.
“People with asthma may find they need to use their reliever inhaler more often. Older people should also reduce physical exertion.”
It adds: “Anyone experiencing discomfort such as sore eyes, cough or sore throat should consider reducing activity, particularly outdoors”.
A Defra spokesperson said to the BBC: “The high level of air pollution this week is due to light easterly winds continuing to bring in pollutants and allow local pollutants to remain close to source. There may also be some component due to Saharan dust.”
The EU has launched legal proceedings against the UK for a longstanding failure to reduce “excessive” levels of nitrogen dioxide (NO2) air pollution, which is mostly from traffic, despite 15 years of warnings, said the BBC’s environment correspondent Roger Harrabin.