Air pollution is to blame for one in three cases of asthma-related hospitalisation around the world, research from George Washington University suggests.

Up to 33 million visits to A&E for asthma worldwide may be triggered by breathing in air polluted by ozone or fine particulate matter, the researchers said.

The news comes as separate analysis shows more than 2,000 GP surgeries, clinics and hospitals in Britain are in areas which breach safe pollution limits, with people breathing “toxic air” as they seek medical care.

The second British study, by the British Lung Foundation and Cambridge Environmental Research Consultants (CERC), found some of the country’s biggest children’s hospitals are situated in areas with high levels of pollution.

Great Ormond Street in London, and Birmingham’s Children Hospital, are both situated in locations that exceed the World Health Organisation’s recommend limit of tiny particle pollution known as “particulate matter” or PM2.5. 

These particles, the majority of which come from road transport in urban areas, have been linked to causing and worsening diseases including asthma, coronary heart disease, stroke, and lung cancer.

In England, one in three GP practices and one in four hospitals are located in areas that exceed the safe levels, according to the UK study, which analysed the postcodes of 9,988 NHS health centres against data for PM2.5 levels.

In Wales, 54 GP surgeries and three hospitals are in polluted areas, with Cardiff seeing the highest levels of PM2.5, and in Scotland three healthcare sites are above the recommended limit, in Aberdeen, Falkirk and Berwickshire.

Meanwhile the US study said approximately 95 per cent of the world’s population lives in places with unsafe air. 

Susan C. Anenberg, associate professor at George Washington University, commented: “We know that air pollution is the leading environmental health risk factor globally. Our results show that the range of global public health impacts from breathing dirty air are even more far reaching―and include millions of asthma attacks every year.”

Alison Cook, director of policy at the British Lung Foundation, said: “It can’t be right that hospital staff and GPs must care for people in environments that could worsen their symptoms and could be putting them at risk of a whole range of health problems further down the line.

“The ball is now in the Government’s court; we want them to adopt WHO’s limit and ensure we meet it.”