Introduction

Local Authorities are required to submit an Annual Status Report (ASR) to DEFRA at the end of June every year. This includes air quality monitoring results and progress on their Air Quality Action Plans for the previous year.

Our 2025 ASR was submitted to DEFRA on 30 June 2025. They accepted it on 22 August 2025. The main findings of the report are below. You can read the full report on the Kent Air website.

Monitoring results

In 2024, we undertook non-automatic (passive) monitoring of nitrogen dioxide (NO₂) at 33 sites. 25 sites had lower NO₂ levels in 2024 than they did in 2023. Seven of the sites had the same level of NO₂ in 2024 as they did in 2023, and only one site showed an increase in 2024 compared to 2023. As was the case in 2023, there were no exceedances of any Local Air Quality Management (LAQM) objectives outside of the Upper Stone Street Air Quality Management Area (AQMA).

Inside the Upper Stone Street AQMA, the trend of decreasing NO₂ levels continued in 2024. Although significant exceedances of the NO₂ annual mean objective remain, levels have reduced at every diffusion tube site compared to 2023.

For the second consecutive year, no site in Upper Stone Street recorded an NO₂ annual mean level above 60 micrograms per cubic meter of air (µgm^-3).  As discussed in the 2024 Air Quality Status Report (ASR), based on the results of tubes Maid 123, Maid 128, Maid 142, Maid 143, and the automatic monitoring station, the Western side of the Upper Stone Street AQMA already appears to be compliant with all AQ objectives. There was a slight increase in the NO₂ annual mean level recorded at the automatic monitoring station, although we think that the level recorded in 2023 was anomalously low, and that the 2024 result was simply a correction of the trend.

Overall, the trend is still downward.  The monitoring station has a diffusion tube (Maid 128) collocated with it, which does not reflect the small increase in NO₂ levels measured by the automatic monitor.  NO₂ results from the monitoring station and the diffusion tube are below, along with results from the Detling monitoring station for comparison. The results from Detling, which is a rural site, are consistently below 10µgm^-3.

Mean air quality trends in Maidstone (2020 - 2024)

The data from monitoring nitrogen dioxide (NO₂) levels across Maidstone are positive. This is compared to the UK’s objective of 40 µg/m³. It has shown encouraging improvements in air quality over recent years at our monitored sites:

• Maid128
• Detling
• Upper Stone Street

Data for Maid128 shows that:

• NO₂ levels were above the objective in 2020
• there has been a steady decline each year
• by 2024, levels are closer to meeting the target, though still slightly above

Data at Detling shows:

• NO₂ levels have remained consistently low and well below the objective throughout the five years
• this location continues to perform well in terms of air quality

Upper Stone Street data shows that:

• in 2020 it started with high NO₂ levels, exceeding the objective
• there is a strong downward trend through the years recorded
• by 2024, levels are nearly within the objective range, reflecting significant improvement

In Upper Stone Street, there was a small increase in the Particle Matter 10 (PM₁₀) annual mean level in 2024, to 19µgm^-3, from 17µgm^-3 in 2023. We believe this may have been a result of a number of pollution episodes on the continent in 2024. Unlike the case with NO₂, a significant proportion of PM₁₀ is from non-local and non-traffic sources.  In the rural monitoring site at Detling, the PM₁₀ level remained constant at 12µgm^-3, the same level as in 2023.  The general trend is downward at both sites, but levels have been well below the objectives for many years.

We have also seen a downward trend in Particle Matter 2.5 (PM₂.₅) levels in Upper Stone Street, with the PM₂.₅ annual mean level in 2024 being 10µgm^-3, which represents compliance with the current and proposed future objectives.  The current target is 20µgm^-3, which will be reduced to 12µgm^-3 in 2028 and to10µgm^-3 in 2040.

Mean PM₁₀ air quality trends in Detling and Upper Stone Street (2019 - 2024)

The data from monitoring particulate matter (PM₁₀) levels across Detling and Upper Stone Street is positive. This is compared to the UK’s objective of 40 µg/m³. It has shown encouraging improvements in air quality over recent years at Detling and Upper Stone Street. Data for Detling shows that:

• PM₁₀ levels were below the objective in all years
• there has been a steady decline each year

Data at Upper Stone Street shows:

• PM₁₀ levels have remained consistently low and well below the objective throughout the five years
• this location continues to perform well in terms of air quality

Mean PM₂.₅ air quality trends (2019 – 2024)

The data from monitoring fine particulate matter (PM₂.₅) levels shows a positive downward trend. This is compared to the UK’s air quality standard (AQS) objective of 20 µg/m³. Over recent years, the data indicates a steady improvement in air quality. In 2019, PM₂.₅ levels were around 18 µg/m³. This is below the AQS objective but still relatively high. Each year has shown a gradual decline in PM₂.₅ concentrations.

By 2024, levels fell to approximately 10 µg/m³. This downward trend reflects a consistent and encouraging improvement in air quality.

Changes to the monitoring provision in Maidstone

We have been aware that the rural monitoring station in Detling has been on borrowed time for the last few years.  The monitoring equipment was both old and obsolete, with no readily available supply of spare parts, either for routine servicing or for equipment repairs. It was understood that once the equipment failed, there was unlikely to be a budget for its replacement.

The station is situated on land which belongs to Kent County Showground, and for many years they have let us use it for a very reasonable rent. The last five-year lease was drawn up at a charge of £330 per year. At the end of the five years, we approached the Showground about a shorter lease term, due to the age of the equipment. However, they decided to increase the term to ten years at a rent of £2,500, which made retaining the site impractical. We kept it going until the end of December in order to complete the 2024 data set, after which the instruments were switched off and removed, and the site decommissioned. The Environment Agency has also been using the site for some of its monitoring, and it will continue to maintain a presence on the site. They have taken over the lease with Kent County Showground.

In another change to our automatic monitoring sites, the PM₁₀ and PM₂.₅ monitoring at Upper Stone Street has been absorbed into the Automatic Urban and Rural Network (AURN), with the Beta Attenuation Mass Monitor (BAM) instruments replaced with a new FIDAS. This also took place in December 2024. We are optimistic that we will see continuity of data between the new and the old instruments.

Future plans

Our main air quality priority for the coming year is the remodelling of the Upper Stone Street AQMA described above. The work will be undertaken based on the 2024 air quality data, and therefore, the start of the work is expected to coincide with the publication of the 2025 ASR.

Since a significant proportion of the receptors in Upper Stone Street are known to be at first-floor level, the modelling is essential because we cannot easily measure at these receptors directly. The number of receptors in excess is expected to be very low, and we need to keep a close eye on them in order to understand when the AQMA reaches full compliance with the NO₂ annual mean objective. The previous modelling on which the current AQMA was based predicted that there would be 27 receptors still exceeding the NO₂ annual mean by 2022. However, we have continued to see air quality improvements in 2023 and 2024, so this number can now be expected to be even lower.

We also plan to undertake a more detailed review of NO₂ levels across the Borough to assess how ready we might be for a potential change in the NO₂ annual mean in line with the new EU objective of 20µgm^-3 expected to come into effect in 2030, and with our longer-term ambition to meet WHO AQ objectives in the future.

Finally, we intend to undertake a source apportionment exercise for PM₂.₅ in the Borough. It is quite possible that in the fairly near future, PM₂.₅ will become a more pressing air quality priority than NO₂, as NO₂ objectives are mostly met, and the health issues associated with PM₂.₅ become more clearly understood. It is already clear that traffic is almost certainly not the major source of PM₂.₅ in the district, but in order to try to reduce levels, we do need a better understanding of where it originates from. We do not intend to model PM₁₀ at present because of the likely cost and because PM₁₀ levels are very low relative to current objectives.

Progress on AQAP

The current AQAP was published in December 2023, so 2024 was our first year working on the actions. Progress is monitored regularly at our quarterly steering group meetings, which are comprised of officers from the relevant departments at KCC and MBC, local ward members, and the portfolio holder.  The progress indicated below was as reported in the 2025 ASR, which covers the calendar year of 2024, so it is not necessarily completely up to date.

Improvements to the bus fleet

The modelling on which the AQMA was based showed that Maidstone’s elderly bus fleet was a significant contributor to poor air quality in Upper Stone Street in 2019, and that replacing this fleet with a fleet of Euro VI or electric buses would result in a significant air quality improvement. Over the period of the COVID pandemic, the bus fleet did improve (without our intervention), and the latest figures we have are shown below.

We believe that these improvements in the bus fleet are likely to be a major factor in the improvements in air quality in Upper Stone Street that have occurred in 2023 and 2024.

During 2024 we established the Maidstone Local Bus Focus Group, of which the inaugural meeting took place on 4 December 2024. The meeting included representatives of the council, bus companies and KCC. We hope that this group can help to facilitate further improvements in the bus fleet in future. Some of the other key actions from the new Action Plan we have been working on in 2024 are listed below.

Information campaign to residents of the new AQMA

As part of this action, we plan to introduce some street signs to inform people that they are in an AQMA. A design for this sign has been chosen and is shown in Figure ES.3. We have yet to determine the exact locations for these signs.  We will develop additional strands to this action in due course, with the help of our Communications Team. However, we now feel that it would be prudent to await the results of our updated modelling work in 2025 to understand how many receptors are still in excess and where exactly they are located.

Extension to the Clean Air for Schools programme

We have been pleased with the Pollution Patrol resource, which was developed by TMC Communications Ltd as part of a DEFRA-funded project. The lead partner in the project is nominally Tunbridge Wells Borough Council, but the project is being delivered jointly by staff from the Mid Kent Environmental Services partnership of Tunbridge Wells, Maidstone, and Swale Borough Councils. Unfortunately, the take-up amongst schools has been disappointing, despite several initiatives to promote the project.

Clean Air Academy

We will prioritise the AQMA and surrounding areas for roll-out of the new DEFRA-funded Health Professionals AQ resource, now known as Clean Air Academy. Work on the resource has progressed well during 2024.

Anti-idling campaign

This is a campaign of anti-idling signage across the Borough, focusing on schools and other known or identified problem areas. Two different styles of anti-idling signs have been designed; one for the Mid-Kent shared service and one based on artwork from the Pollution Patrol Project.

A modest start has been made on deploying these signs, with about 20 having been deployed to date, in priority locations near schools. Another five locations have been identified for which permission is being sought from KCC to affix our signs to their lamp posts.