The British Lung Foundation has said the number of towns and cities breaching standards for the smallest pollution particles is "deeply concerning".
York and Middlesbrough are among those who have been named bythe World Health Organisation for breaching safe levels for fine particles inthe air, known as PM2.5.
:: Longford, Ireland
:: Port Talbort
:: Bray, Ireland
:: Leamington Spa
:: Galway, Ireland
:: Dublin, Ireland
How is the air quality measured?
One way the global health body assesses air quality is by examining the levels of a type of pollution known as particulate matter (PMs).
WHO's latest data shows that 11 urban areas across the UK and Ireland breached the safe limit set for PM10.
These include Port Talbot, Stanford-Le-Hope, Glasgow, London, Scunthorpe, Leeds, Eastbourne, Nottingham, Southampton and Oxford, as well the town of Longford in Ireland.
More than 40 towns and cities across Britain and Ireland breached the safe levels for another measure known as PM2.5.
WHO said that across the world 80% of cities that measure outdoor air pollution are failing to meet its guidance for safe levels of air quality.
As air quality declines, the risk of stroke, heart disease, lung cancer, andchronic and acute respiratory diseases, including asthma, increases for thepeople who live in these areas - according to health experts.