Bath's Clean Air Zone continues to improve air quality across the city

Bath’s Clean Air Zone (CAZ) is continuing to improve air quality with a decreasing trend in nitrogen dioxide concentrations across the city, according to new data published this week. 

The 2022 Annual CAZ report published by Bath & North East Somerset Council this week notes that compared with 2019, there has been a 26% reduction in annual mean nitrogen dioxide (NO2) within the zone, representing an average reduction of 8.5 micrograms per cubic metre (μg/m3).

In the urban area outside the zone, there has been a 27% reduction in annual mean NO2 concentrations (an average reduction of 7.1 μg/m3) with nine fewer sites exceeding the legal limit of 40 μg/m3 falling from 10 sites in 2019 to one site in 2022.

The figures also indicate an additional reduction of 6% in annual mean NO2 concentrations in 2022 compared with 2021, as well as a reduction of 7% within the CAZ boundary.

This data indicates air quality has improved both within the CAZ and the areas which immediately surround it, with indications, too, of improvements to air quality across the wider Bath & North East Somerset area as well.

Compliance has also significantly improved with 71% fewer polluting vehicles driving in the zone by the end of December 2022 – an average of 497 vehicles per day - compared with an average of 1,742 vehicles in the first week the CAZ launched in March 2021.

The report also notes the impacts of Covid-19 and the partial closure of Cleveland Bridge from October 2021 to October 2022 on the volume and direction of traffic through the city, meaning that clear conclusions on traffic displacement in 2022 cannot be drawn. The council has submitted its air quality data to the government’s Joint Air Quality Unit (JAQU) which is due to publish a progress report later this year.

The council has also recently published its Air Quality Annual Status report for 2023 which shows that from NO2 monitoring at four continuous analysers in 2022, all results were below the annual average objective. There was one exceedance of the 1-hour objective at the Bath A4 site, however, 18 exceedances are allowed.

Councillor Sarah Warren, Deputy Leader and cabinet member for Climate Emergency and Sustainable Travel, said: “It’s heartening to see the clear indications in this report that the clean air zone is working to improve air quality across the area, not just within the zone."

“Air pollution is a significant risk to people’s health, which is why the Government directed us to implement the CAZ."

“The partial closure of Cleveland Bridge and the impact of the Covid-pandemic on traffic flow means that we cannot draw clear conclusions on the impact of the zone on traffic displacement in 2022, however we await the government’s review of our data to confirm whether the CAZ has achieved success."

“The upturn in compliance demonstrates support from the public which should be applauded, but we recognise that there is still more to do to drive down pollution at all locations in Bath. Looking ahead, we’ll pay particular attention to sites that continue to exceed legal limits and find specific solutions to combat this. We will also continue to promote sustainable travel alternatives to the car which will increasingly enable people to walk, cycle or wheel for healthier short journeys around the city, reducing both pollution and carbon emissions from transport.”

The council’s £9.4 million financial assistance scheme to help local businesses and individuals replace or upgrade polluting vehicles with cleaner, compliant ones saw owners of more than 1,500 vehicles apply for support. 938 polluting vehicles were replaced or upgraded through the scheme by the end of 2022.

Bath's CAZ was launched on 15 March 2021 to urgently tackle harmful levels of air pollution caused by the most polluting taxis, vans, buses and larger commercial vehicles regularly driving in the city.

It was the first to be launched outside London and works to reduce pollution in Bath by levying a £9 or £100 a day charge on anyone driving a chargeable higher emission vehicle in the zone. This excludes private cars and motorcycles which are not charged. 

The charges are designed to deter higher polluting vehicles from entering the zone, while also speeding up the natural replacement rate of polluting vehicles in exchange for cleaner ones. Any revenue over and above the operating cost will be spent on supporting sustainable transport projects or schemes which contribute towards improvements to air quality.