Glasgow is one of the UK's most polluted cities, according to a new World Health Organisation report.

It warned millions of people are inhaling air considered too dangerous to breathe.

Out of 51 UK cities and towns listed in an air quality database, 44 fail the WHO's test for fine sooty particles smaller than 2.5 microns across.

These have been linked to heart disease and premature death.

The WHO said exposure to the particles, known as PM2.5s, should not exceed ten micrograms per cubic metre of air.

It is claimed annual average levels are higher, sometimes by a significant degree, across the UK.

Glasgow was found to have a PM2.5s concentration of 16 micrograms per cubic metre.

This compares to 15 in London and Leeds, 14 in Cardiff and Birmingham and 13 in Manchester.

Each year, outdoor air pollution is estimated to cause 40,000 premature deaths in the UK - up to 9000 in London alone - and cost the country £22.6bn.

Dr Toby Hillman, one of the report's authors from the Royal College of Physicians, said: "There isn't a safe limit for the amount of pollution that's been defined as yet and we know the effects of poor air quality run from cradle to grave - it's a lifetime threat to human health.

"This is a really direct and tangible impact on UK health from the drivers of climate change, and taking action on air quality should be a priority."

The impact of air pollution in UK cities forms part of a major investigation looking at the health and social costs of climate change around the world led by a leading medical journal.

The Lancet Countdown on Health and Climate Change brought together 24 institutions and inter-governmental organisations including the WHO and World Meteorological Organisation.

It found global exposure to dangerous levels of air pollution caused by burning fossil fuels had increased by 11.2% since 1990 with more than 70% of cities exceeding WHO PM2.5 limits.