In this post we take a quick analysis of Air Quality across Chippenham in the December 2024 to early January 2025 time period. Specifically we look at small particulate pollution PM2.5 in the four monitoring locations across Chippenham.
What are the standards?
The Air Quality standards 2010 state that an annual average for PM2.5 shouldn’t exceed 20ug/m3.
The World Health Organisation (WHO) has set tighter limits for particulates. The current guidelines state that annual average concentrations of PM2.5 should not exceed 5 µg/m3, while 24-hour average exposures should not exceed 15 µg/m3 more than 3 – 4 days per year.
What are the sources of PM2.5 particulates?
Outdoor PM2.5 particulates can have a number of sources:
- Vehicles: Exhaust emissions from cars and trucks; tyre and brake wear
- Power Plants: Emissions from Power generation facilities
- Industrial process emissions
- Fires such as agricultural burning and wood burning stoves
- Construction sites
- Dusty roads and other particles from roads
Why is PM2.5 of concern?
PM2.5 particulates have been linked to a number of health conditions including bronchitis, asthma attacks, lower respiratory infections, increased risk of heart attack and stroke, lung disease, types of lung cancer, and increased risk of premature mortality.
So let’s take a look at the December 2024 to January 2025 PM2.5 measurements at the four monitoring sites – Langley Road, Marshfield Road, Rowden Hill, and Wood Lane.
Langley Road
Our first monitoring location is Langley Road, Chippenham.
The average PM2.5 level over the monitoring period is 13.9 ug/m3. Whilst this is under current UK air quality limits, it is two to three times the World Health Organisation (WHO) recommended annual average of 5ug/m3.
Langley Road continues to show high spikes of emissions – what could be the cause of this?
It’s hard to answer this definitively, but there are a few possible causes…
- Wood Burning – the neighbour at the test site lights a wood burning stove each morning. The direction of the initial smoke is such that the monitoring location needs to turn off their ventilation system for two hours each morning to avoid filling the upstairs with the smell of wood smoke. So it could be wood burning related.
- Traffic – the location rarely has queuing traffic outside, but over the measuring period at times traffic did queue outside the test location.
- Industrial processes – the near by plastics plant does sometimes result in the smell of burnt plastic at the location
- Construction pollution – The nearby demolition of the old Westinghouse site is close by.
- Power Station emissions – There is a 10MW gas fired peaker generator at nearby Cockleberry Lane, though it is unknown when this is active.
- Equipment fault – it’s possible that the very high spikes are erroneous. The test location has recently had an air sourced heat pump installed and that too has an air quality monitor that typically correlates with the test equipment. Though historic data isn’t currently available to see if it too measures very high spikes.
Average 13.9 ug/m3 PM2.5
Peak
| 0FRW1BF14G9S6S7TTHGWHBA7B6 | 20 | 2615745 |
2024-12-21 00:44:09 UTC
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| 0FRW2DSNCGZ853TG60WX0X1R57 | 200 | 2615745 |
2024-12-21 01:44:09 UTC
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| 0FRW3G49MGH9SFAK6SHDDHX5M9 | 8 | 2615745 |
2024-12-21 02:44:09 UTC
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| 0FRW4JEXWGHXQPHXAASNECE36Z | 1344 | 2615745 |
2024-12-21 03:44:09 UTC
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Marshfield Road December PM2.5
The Marshfield Road monitor is situated on one of the busiest Chippenham Roads, though it is shielded by a large evergreen hedge.
The average for the month of 13.77ug/m3 is similar to the Langley Road average and is within UK air quality standards, though two to three times higher than WHO guidelines.
The site also shows levels consistently above 40ug/m3.
The most likely source of emissions at this location is road traffic.
Average 13.77 ug/m3
The chart shows the period 12th December 2024 to 1st January 2025.
Rowden Hill December PM2.5
The Rowden Hill location is again one of the busiest road traffic locations in Chippenham with frequent queuing traffic at the location.
The average over the measurement period of 14.7ug/m3 is within UK limits but again two to three times higher than WHO guidelines.
The level frequently exceeds 40ug/m3 for several time periods.
The most likely cause is road transport emissions.
Average 14.7 ug/m3
Wood Lane December PM2.5
The Wood Lane location shows the best Air Quality of the four measuring locations with an average over the period of 3.6ug/m3, the only location below WHO guidelines.
The chart covers the same time period as Rowden Hill and does show a trend to worsening Air quality in the early to mid January period.
This may be down to the return to work and increase in traffic levels. It also spanned a period of colder weather.
Average 3.6 ug/m3
Conclusions
The average PM2.5 levels over the month across all four measurement sites were within UK Air Quality limits. However the Rowden Hill, Marshfield Road, and Langley Road site exceeded WHO guidelines by two to three times.
Rowden Hill had the worst air quality and Wood Lane the best.
All sites showed high levels of PM2.5 particulates for defined periods, and the Wood Lane and Rowden Hill site show a trend of worsening Air Quality from Christmas to mid January. This could be due to the return to work and higher traffic volumes, or possibly related to the cold weather spell.
Both the Langley Road and Marshfield Road unit batteries fully discharged at the beginning of January and so don’t cover this January period.
The Langley Road site continues to show very high spikes in particulates for which the cause is unknown.