Brits with health conditions are being urged to stay indoors, as a rise in pollution levels puts them at risk.
High air pollution warnings have been issued for parts of England, such as the Midlands, the South East, and North West.
The high alert is in place from London to Ipswich and Cambridge, as well as further north to Nottingham and to Hull.
According to the Department for Environment, Food and Rural Affairs (DEFRA), Leicester, Northampton, and Manchester are also among the places affected, along with spots along the south coast, including Brighton, Eastbourne and Hastings.
Advice issued by DEFRA suggests 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,” the group added.
Additionally, anyone experiencing discomfort such as sore eyes, cough or sore throat was advised to consider reducing activity, particularly outdoors.
According to Sky News, Mayor of London Sadiq Khan warned that toxic air “is dangerous”, particularly for those with heart and lung problems.
He urged residents to look after each other by walking, cycling, avoiding unnecessary car trips and stopping engine idling.
He also asked people to withhold from burning wood or garden waste.
Earlier this year Mr Khan said car use had returned to close to pre-pandemic levels and that the effect on residents could be disastrous.
“If we do not double down on our efforts to deliver a greener, more sustainable future, we will replace one public health crisis with another – caused by filthy air and gridlocked roads,” he said.
In January, a candlelit-vigil was held in south London by the mother of Ella Adoo-Kissi-Debrah on what would have been her 18th birthday.
She died in 2013 aged just nine-years-old following an asthma attack.
In December 2020, she became the first person in the UK to have air pollution listed as a cause of death after a second landmark inquest.
Southwark Coroner's Court found that air pollution "made a material contribution" to Ella's death.
She lived with her her family close to the South Circular Road in Lewisham, south-east London Prof Gavin Shaddick, a government adviser on air pollution, called it "a landmark decision".
According to a survey by Kleenex, two thirds of hayfever sufferers believe pollution is the biggest factor that affects their allergies.
