A key focus and commitment for Think Air is to work with schools throughout the UK to monitor air pollution at low-cost and help children, parents and teachers better understand air quality and how they can protect their health from the impacts of pollutants.
One of the first Think Air monitors that we installed was at Ysgol Y Bedol in Garnant, South Wales.
Garnant is a village with a long tradition of mining that is situated in the Amman Valley, north of Swansea. The village is in the county of Carmarthenshire, which has no fixed, continuous air pollution monitors for particulates. Garnant is typical of many ex-mining localities in Wales and, according to the Welsh Index of Multiple Deprivation (WIMD), is in the top third of most deprived areas in Wales by deprivation index. Furthermore, by the same index, the village is also in the top third for worst areas for health.
The reason behind the study.
As well as providing air quality data for the community, Think Air was also able to analyse the patterns of PM levels at Garnant during the COVID-19 pandemic in 2020.
It is well documented by Think Air and others that levels of NO2 fell significantly in Wales immediately after lockdown restrictions were introduced in late March 2020, due to the huge reduction in traffic on roads19.
PM2.5 levels however were observed to have increased during late March, and at many times throughout April at the urban AURN monitoring stations in Swansea, Cardiff, and Newport, as well as the rural background AURN at Narberth.
It was considered by experts that the increased particulate levels were mainly due to people spending more time at home and burning more through domestic burners and garden fires as well as famers spreading slurry across Wales, England and beyond.
Media coverage at the time reported large reductions in air pollution, due to the NO2 levels but in reality many people were being exposed to high levels of particulates.
It is hardly surprising that a lack of information existed on higher PM levels in Welsh Cities, given that the media weren’t reporting it and that forecasts are often inaccurate.
The lack of PM monitors in the rest of Wales at that time meant it was unknown if the high PM levels were just occurring in the cities, or regionally across the principality.
By having continuous PM data recorded at Ysgol Y Bedol, we were able to quickly make comparisons between levels in this remoter part of Wale, the urban background AURN station at Cardiff, and the rural background AURN in Narberth (Figure 5) from the beginning of the 2020 COVID-19 pandemic lockdown (March) through the rest of the year.
We observed that the pattern of PM levels closely followed that of Cardiff and Narberth, revealing that when concentrations are high in large urban areas, they are also high in more remote areas – towns and villages that have no monitoring data. Critically, children at a school in Garnant are likely exposed to similar PM levels as children in Cardiff. The data also showed that there were days, when PM concentrations were high, when levels in Garnant exceeded levels in Cardiff.
We were also interested to know if the increased PM levels in Garnant during March and April were caused by particulates being blown into the area from sources outside of Wales – as had been proposed for Swansea and Cardiff. Our Think Air modellers therefore used weather data, and a method called back trajectory modelling, which did show that increased PM levels at the school were caused by particles being blown from some distance (Figure 6).
Indeed, the models show that in March, PM levels were reaching Garnant from as far afield as Germany and Poland – likely due to ammonia emissions being converted to PM from famers spreading slurry in these regions.
Similarly, in April, models showed PM levels to likely be increased in Garnant due to particles from Belgium and Holland.
We extended our analysis by carrying out back trajectory modelling for the period between March and October so that we could get a more complete picture of where PM in Garnant comes from day by day.
Using cluster analysis, we were able to group days together based on wind direction and wind speed and how far particles had travelled from source to Garnant.
The left-hand plot in Figure 7 shows that 10 clusters represented trajectories from all wind directions, and we observed that two of these clusters (labelled A and B) represented easterly winds from Northern Europe.
The right-hand lower plot in Figure 7 shows how these trajectory clusters map onto each day throughout the period.
There is also a clear pattern showing that when PM levels are high during the year at the school in Garnant, it is mainly due to pollution from outside of Wales and even outside of the UK blown in by easterly winds.
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