Glasgow LEZ impact 'encouraging' as report shows air pollution drop

A sign warning road users that they're entering a low emission zone in the city centre of Glasgow,
-Credit: (Image: Reach Publishing Services Limited)


Air pollution in Glasgow city centre has reduced since the Low Emission Zone was rolled out, new research has shown.

The city council’s air quality report for 2023 — the first since the LEZ came into force — has revealed nitrogen dioxide (NO2) levels have dropped by 20% in the city centre and LEZ area.

A 15.3% drop was also reported in NO2 levels at locations outside the city centre, but some areas of concern within the LEZ do remain.

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Cllr Angus Millar, SNP, the city convener for transport and climate, said the early progress was “really encouraging”.

Enforcement of the LEZ, which has been introduced to reduce levels of harmful emissions, began in June 2023. It prevents the most polluting vehicles entering the city centre zone.

The council report states the “main source of air pollution produced within the city itself comes from road traffic”. NO2, produced by the combustion of fossil fuels, can be “more directly attributed to local traffic volumes and engine type”, particularly diesel.

Air pollution is observed by 11 automatic monitoring stations around the city. All stations recorded levels of NO2 “below the objective levels, continuing the trend of compliance observed in 2022”.

Diffusion tube monitoring is also carried out, allowing checks at “more locations than is economic or practical using automatic stations”. However, the method is “less accurate”.

The annual objective was exceeded at two locations where diffusion tube monitoring occurs, down from four in 2022. These were Gordon Street, where there is a taxi rank serving Central Station, and under the Heilanman’s Umbrella.

However, the council report states there is “poor dispersion” under the railway bridge at Heilanman’s Umbrella. It will continue to be monitored.

Compliance with legal levels at all automatic monitoring stations was met, but only narrowly at Hope Street.

The council said as the LEZ was only in force for half of 2023, it is too soon to determine the full impact on air quality. Exemptions, to allow time to comply with the rules, were issued to 778 taxi drivers and residents didn’t need to comply until June this year.

Cllr Millar said: “Air pollution contributes to hundreds of deaths in Glasgow each year, as well as exacerbating long-term health inequalities and the health conditions of thousands of Glaswegians.

“Glasgow’s LEZ was introduced to address stubbornly high levels of air pollution in the city centre — and with Dundee, Aberdeen and Edinburgh now implementing their own LEZs, Scotland’s cities have joined hundreds across Europe in taking this kind of action to improve air quality.

“The early progress recorded in Glasgow in 2023 — with a 20% drop in the city centre’s nitrogen dioxide levels — is really encouraging.

"With some locations still showing breaches of legal limits, however, the impact of the LEZ’s full roll out will only become clear with next year’s annual monitoring data, and Glasgow will continue our work to seek cleaner, more breathable air that meets legal requirements.”

The University of Glasgow has also carried out two separate three-month studies, in 2022 and 2023, at two monitoring stations.

That work, carried out with researchers from the University of Auckland and University College Dublin, gathered data from traffic sensors and air quality monitors in Hope Street and High Street. Weather conditions were taken into account.

The study found a significant reduction on High Street during weekdays, resulting in decreases in NO2 levels between 25 and 27%, with a 35% drop at weekends.

On Hope Street, traffic patterns were stable but decreases in NO2 levels of between 9 and 13% were observed.

Qunshan Zhao, professor in urban analytics in the school of social and political sciences at the University of Glasgow: said: “These early results indicate that while traffic reductions and the decrease of the high emission vehicles in some parts of the city may be contributing to improved air quality, other factors play a role.

“The findings highlight the need for continued monitoring to better understand the LEZ’s long-term impact on both traffic and pollution levels across Glasgow.”

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