Sudden spikes in air pollution in the UK trigger hundreds more heart attacks, strokes and acute asthma attacks on those days, research suggests.
A team at King’s College London looked at data from London, Birmingham, Bristol, Derby, Liverpool, Manchester, Nottingham, Oxford and Southampton.
Days when pollutant levels were in the top half of the annual range saw an extra 124 cardiac arrests on average.
NHS England boss Simon Stevens said it was evidence of “a health emergency”.
The figure is based on ambulance call data and does not count heart attacks suffered by patients already in hospital.
It points to significant short-term health risks caused by air pollution, on top of contributing to almost 500,000 premature deaths in Europe every year.
On days with high pollution levels, across the nine cities in total, there was an average of 231 additional hospital admissions for stroke, with an extra 193 children and adults taken to hospital for asthma treatment.
Dr Heather Walton, of King’s College London’s Environmental Research Group, said air pollution reduction policies concentrated in the main on effects connected to life expectancy.
“However, health studies show clear links with a much wider range of health effects,” she added.
In London, high-pollution days caused an extra 87 cardiac arrests on average, an extra 144 strokes, and 74 children and 33 adults ending up in hospital with asthma-related issues.
Birmingham saw 12 more out-of-hospital cardiac arrests, 27 additional admissions for stroke and 26 more for asthma.
Bristol, Liverpool, Manchester, Nottingham, Oxford and Southampton saw between two and six more out-of-hospital heart attacks and up to 14 extra hospital admissions for both stroke and asthma on high-pollution days.
Only in Derby was there no apparent increase.
Among the long-term risks associated with high pollution levels are stunted lung growth and low birth weight.
The King’s College research also suggests cutting air pollution by a fifth would decrease incidents of lung cancer by between 5% and 7% across the nine cities surveyed.
Mr Stevens said: “It’s clear that the climate emergency is in fact also a health emergency.
“Since these avoidable deaths are happening now – not in 2025 or 2050 – together we need to act now.”
The figures were published ahead of Wednesday’s International Clean Air Summit hosted by Mayor of London Sadiq Khan and the UK100 network of local government leaders.
UK100 director Polly Billington said: “Local government needs additional powers and resources to address this public health crisis.”