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The World Heath Organisation has apologised and admitted figures it published which identified Port Talbot as the most polluted town in the UK were wrong.

The global body has said it made an “oversight” in data which suggested that Port Talbot had more air pollution than the UK’s biggest cities.

On Wednesday, a WHO database was published which suggested the south Wales town had a fine pollution level of 18 micrograms of M2.5 pollution particles per cubic metre of air.

This compared to 14 micrograms in London and 13 in Manchester - all above a national guideline of 10 micrograms.

(Image: Matthew Horwood)

But the figure has now been described as “erroneous” by WHO director Dr Maria Neria after being challenged by Neath Port Talbot council.

In a letter addressed to the council, Dr Neria said the air pollution level for Port Talbot was instead measured at 9.6853 micrograms- just under half of the figure originally given and below WHO air pollution guidelines.

She said: “The PM2.5 level for the year 2015 for Port Talbot should be 9.6853 (and is rounded to 10 in the updated excel sheet) and is noted as ‘measured’.

“The PM2.5 was erroneously featured as a converted (estimated) value of 18.

“The World Health Organisation has taken immediate steps to rectify this on its WHO web site, and in the database. We regret that this error happened.”

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In the WHO database, two types of air particles are measured - larger sized PM10 particles and smaller and “especially dangerous” PM2.5 particles.

According to the organisation, figures from Port Talbot PM10 air pollution levels had been measured in 2015 and converted to PM2.5 particles to reach an estimated figure.

In October a separate study also found that Cardiff , Swansea , Port Talbot, Newport , Chepstow and Wrexham were over the limit for air pollution limit.

The data, published by the Royal College of Physicians and Lancet Countdown, found Port Talbot to have 14 micrograms per cubic metre of average annual PM2.5 numbers.

(Image: Richard Swingler)

The European Environment Agency also found the town to have an average of 9.69 micrograms per of air pollution per cubic metre in 2015.

In Port Talbot, proposals have been made to extend the 50mph speed restriction on the M4 in a bid to cut nitrogen dioxide (NO2) levels.

The restriction currently applies to a stretch of motorway, between where it passes over Taibach and junction 41, adjacent to Neath Port Talbot Hospital, which is around 3km.

But under the new temporary measure, which is set to be introduced within the next two months, the restriction will be extended west to junction 42, the main Swansea turn-off.

WHO has been contacted for comment.