Air pollution warnings have been issued across the UK as local emissions, poor-quality air from the continent, and light winds combine to create potentially hazardous conditions.
Mayor of London Sadiq Khan issued a high pollution alert for the capital in Tuesday, while the government’s air quality information service found particulate matter in the East Midlands and West Midlands to be particularly high.
Similar warnings have been issued this week for towns and cities across the north of England, including Leeds, as well as Scotland and Northern Ireland.
The mayor’s office said there had been poor air quality in London since Sunday evening as a result of local emissions which have failed to disperse and particle pollution from Germany and France.
Pollution in the capital was expected to worsen on Tuesday, prompting an alert will be broadcast across 2,500 bus stop and river pier signs and at entrances to all 270 Tube stations. Roadside message boards on the busiest main roads will flash instructions to drivers to switch engines off when stationary.
It is the 101th time the air quality alert system, which also involves social media and text alerts, has been used since Mr Khan became mayor in May 2016.
Last year he launched an ultra-low emission zone, in which drivers of polluting vehicles pay extra charges, in a bid to tackle toxic air.
Tuesday is forecast to see continued local emissions and the arrival of air from the northern Europe that is even more toxic because it is bringing pollution from a working weekday rather than weekend.
A cloud of Saharan dust was also predicted to worsen air quality in the coming days.
Adults with heart or lung problems and children with lung problems are warned to reduce strenuous physical exertion, particularly outside, during high pollution, while people with asthma may need to use their inhalers more often.
A spokeswoman for the Mayor of London said: “The high levels of pollution expected over the next few days is evidence of the scale of London’s air quality crisis and is exactly why the Mayor is taking hard-hitting measures to clean it up.
“April’s launch of the world’s first Ultra Low Emission Zone (ULEZ) in central London is expected to reduce harmful emissions in the zone by around 45 per cent.
“The Mayor is also cleaning up the capital’s bus and taxi fleets, rolling out rapid charging infrastructure and delivering improvements to schools in some of London’s most polluted areas.”
Mr Khan is to introduce a scrapped scheme to help lower-income households scrap polluting cars later this year, and has called on the government to fund similar proposals across the UK.