Has Dundee LEZ really made our air cleaner?

The Courier

4 days ago

Dundee's low emission zone (LEZ) has been enforced for a year – but is it really making a difference?
Within the first three months of it being in action, the council handed out nearly half a million pounds in fines.
The measures became a source of frustration for the scores of motorists left out of pocket.
But supporters point to the need to keep the most polluting vehicles out of the city centre, to decrease harmful nitrogen dioxide levels branded an 'invisible killer'.
On the first anniversary of the scheme, we reveal the difference the LEZ has made to air pollution in Dundee.
Dundee has six air quality monitoring stations.
Two of them, Whitehall Street and Seagate, fall within the LEZ.
Before the zone was officially introduced all the stations were within the Scottish Air Quality Objective. It sets the target for annual mean nitrogen dioxide levels to stay under 40µg/m3.
The council's website on the LEZ states that there are still locations where that annual level is not being met.
But let's have a look back to before the traffic rules were rolled out.
In 2023, the highest annual mean was recorded at the Seagate station- 28.7µg/m3.
However, as there are seasonal variations in pollution levels, we calculated the average over 12 month periods between June 1 and May 31 the following year.
In the 12 months since the LEZ started to be enforced, there are signs of improvement for the Seagate station.
From June 2024 to the end of May, the average nitrogen dioxide level was 25.24µg/m3. Meanwhile in the preceding 12 months it was 28.87.
But the Whitehall Street monitoring station did not see a very significant change.
In the year before the LEZ, the site started off at a lower average of 20.72 µg/m3. That fell marginally to 20.61 in the year since.
Both stations have been within the Scottish target throughout the period we looked at.
But what do these changes mean? And do they need to continue coming down?
We asked an expert specialising in the impact of air pollution on health.
Professor Jill Belch, clinical professor at the University of Dundee's School of Medicine, has researched how air pollution impacts health.
Higher air pollution is closely linked to rises in hospital admissions to Ninewells, according to her research alongside colleagues at the Tayside Pollution Research Programme.
And that doesn't just include lung problems. For children, who are more vulnerable to air pollution, it can also affect their gut and skin health.
'We do know that for every 10% fall in air pollution over a year, you get a 10% fall in hospital admissions,' Prof Belch said.
So a decrease in the average levels at the Seagate station over 12 months is 'extremely encouraging'.
She added: 'I think that more and more people are beginning to understand the issues of air pollution.
'The problem is that it is invisible, it is an invisible killer. If it were black smoke billowing out of the back of a car, I think people understand more easily that it is very toxic.'
The clinical professor is now looking to study the health benefits of the LEZ by looking at changes in hospital admission data since it was introduced.
While our air pollution objectives are 'the best in Europe', new research suggests that they may still be too high.
Scotland was the first in the UK to take on World Health Organisation (WHO) air quality objectives set in 2005.
But the WHO now suggests that the annual levels should be a quarter of our current goal – just 10µg/m3.
And work by Prof Belch and her colleagues backs that up after showing that children are more sensitive to air pollution concentrations above that limit.
'We are within the current levels, but the current levels are still unsafe,' she warned.
'We do need the LEZs to get our levels even lower.'
The Scottish target focuses solely on the annual average air pollution.
Pollution levels follow seasonal trends and are often higher in the winter when the air is still so an average over a year can be helpful to track changes.
But even day-to-day spikes have an impact on people's health.
'You can be in a situation where the annual measurement is okay but you have days when it is really high and that is when people are being admitted to hospital,' Prof Belch explained.
Dundee monitoring sites do record occasional daily average pollution levels surpassing 40µg/m3, both before and after the LEZ.
In the year since its enforcement, the maximum daily concentration at the Seagate site was 63µg/m3.
That is higher than the peak in the preceding 12 months – 60.4µg/m3.
However, only 7.8% of the 359 measurements since the enforcement surpassed 40µg/m3.
Meanwhile from June 2023 to the end of May 2024, 13.4% of the measurements peaked above 40.
But that change is less apparent on Whitehall Street.
Again, the maximum daily average since the LEZ enforcement was higher than in 2023/24.
Yet it does show signs of decreasing since 2021/22.
A total of 4.2% of measurements surpassed 40µg/m3 in the year since the LEZ. Meanwhile, in the preceding year it was just 1.7%.
Nevertheless, more daily averages exceeded 40µg/m3 than in 2021/22 and 2022/23 – 5.5% and 4.9% respectively.
The Lochee Road station, outside of the LEZ, has seen a consistent decline in NO2 levels since June 2021.
The average for 2021/22 reached 31.4µg/m3. It is now below both the Seagate and Meadowside means.
But even the stations furthest away from the zone, Broughty Ferry Road and Mains Loan, have been falling during the period.
Prof Belch said there 'is a load of benefit' from falls in the levels, but not just for the people living in Dundee.
She said: 'It is worthwhile saying that if you are driving a polluting car that isn't allowed in the LEZ, you are sitting in a basin of pollution within your own car. So are your children and so is anyone that is a passenger in that car.
'Really you are building up health problems for yourself and your family.'
On a day-to-day level, almost all stations surpass a daily average of 40µg/m3 of nitrogen dioxide on peak day.
In fact, the 59µg/m3 daily average from Broughty Ferry Road on January 10 this year marks a new peak in the data going back to 2021.
But the Mains Loan site is an exception. It did not exceed the level in a single daily average in the past 12 months.
While the daily pollution levels still fluctuate within the Dundee LEZ, they didn't surpass 60µg/m3 like they did in 2021.
Broughty Ferry Road actually only saw daily average concentrations spike above 40µg/m3 twice in the past 12 months. That is only 0.57% of the 351 valid measurements.
Meanwhile, at the Meadowside one in ten daily averages site surpassed 40µg/m3. That was the highest proportion across Dundee in the past 12 months.
But as time goes on we will have a clearer picture of LEZ impact.
Data collected so far this year could still see minor modifications as part of a verification process carried out by Scottish Air Quality.
A Dundee City Council spokesperson said: 'Enforcement of the Low Emission Zone commenced on 30th May 2024 with ratified air quality data only available for seven months of the scheme so far.
'The initial performance of the Low Emission Zone has shown positive results which comply with NO2 annual mean air quality objectives. We continue to monitor and evaluate this year-on-year data to gather a more representative trend on the performance of the LEZ.
'The Low Emission Zone is one of many measures being taken by the Council to improve air quality in the city with a new Air Quality Action Plan being developed which will outline further measures up until 2029.'
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