The Glasgow Road assessment and its uncertainty

The 40.8 µg/m³ modelled figure originated in Ricardo Energy & Environment’s Repeat Detailed Assessment of Air Quality at Glasgow Road, Blantyre, dated 30 June 2020 and commissioned by South Lanarkshire Council. The report used ADMS Roads v5.0 to assess NO₂, PM₁₀ and PM₂.₅ over a study area approximately 1.2 by 1.5 km, including Glasgow Road and parts of Station, Stonefield and Bardykes Roads. Its 2019 traffic inputs combined Department for Transport counts with a Council-commissioned survey, projected to 2019. At the first-floor “Glasgow Road 5” receptor, the predicted NO₂ mean was 37.7 µg/m³ with a domain-wide adjustment and 40.8 using a site-specific, explicitly precautionary “worst-case” adjustment. This receptor corresponded to a residential flat above the former co-operative funeralcare office on the south side of Glasgow Road near Station Road. The report estimated up to four flats and potentially nine residents might be exposed if that high modelled value applied, but described the exceedance as very localised and uncertain. Its tables predicted no annual-mean PM₁₀ or PM₂.₅ objective exceedances. (Ricardo repeat detailed assessment at Glasgow Road, Blantyre (2020)) ricardo repeat detailed assessment blantyre 2020

The uncertainty was not merely theoretical. The roadside tube DT32 at 233 Glasgow Road recorded annual means of 56.0 µg/m³ in 2016, 49.6 in 2017, 54.2 in 2018 and 47.3 in 2019, exceeding the 40 µg/m³ objective in each reported year. The nearby DT33 tube at 283 Glasgow Road was substantially lower (33.0, 23.5, 25.5 and 22.6 in those years). In 2019, the automatic SLC09 monitor on the opposite side of the road reported 27.6 µg/m³, but captured only 58% of the year and had a long outage from 1 August to 20 December requiring short-to-long-term adjustment. Ricardo noted a difference of nearly 20 µg/m³ between DT32 and the automatic analyser only a few metres apart; the model initially failed to reproduce it. It was refined to represent traffic directions, building heights and street canyons, road gradients, congestion and parking-bay emissions. The report’s source-apportionment model made diesel cars the largest road NOx source at selected receptors, while heavy vehicles and buses also contributed materially at some westbound locations. All of these apportionment values are model outputs, not direct measurements of each vehicle’s contribution. (Ricardo repeat detailed assessment at Glasgow Road, Blantyre (2020))

On that evidence, the 2020 report said there was not enough certainty to confirm an Air Quality Management Area at the Glasgow Road/Station Road junction, and proposed additional NO₂ monitoring. Its findings were later summarised in Council Annual Progress Reports, including the 2022 report consulted here; the Council’s subsequent twelve-month study in 2022 was a follow-up evidence-gathering exercise, not the same modelling study. The 2019 observation series, modelled 2019 exposure, and later monitor results must therefore remain distinct. The 2020 PDF itself carries an internal “Ricardo Confidential” label, and its maps contain Crown-copyright Ordnance Survey material; this article summarises findings but does not reproduce its figures. (Ricardo repeat detailed assessment at Glasgow Road, Blantyre (2020)) (South Lanarkshire Council, Local Air Quality Management Annual Progress Report 2022) south lanarkshire air quality apr 2022

The 2022 Council report recounts the next stage: a twelve-month study ran from January 2022 to January 2023, using an AQMesh sensor at site DT32 and passive diffusion tubes at ten points along Glasgow Road, including placements to examine first-floor exposure. This targeted design responded to Defra appraisal recommendations about the earlier assessment; it was not a general survey of every neighbourhood or household. The Council’s 2023 report gave the study’s measurements and said it would seek Defra review, which the Council reported in 2024 as accepting its conclusions while advising continued monitoring. south lanarkshire air quality apr 2022 south lanarkshire air quality apr 2023 south lanarkshire air quality apr 2024

What the different measurements show

Environmental Standards Scotland’s independent oversight report records that the diffusion-tube site at 233 Glasgow Road measured an annual-mean NO₂ concentration of 46 µg/m³ in 2020. In the comparison presented by ESS, this was the highest reading among seven sites reporting exceedances or borderline exceedances in that year. The report notes that 233 Glasgow Road lay outside an existing AQMA and that an automatic monitor had been installed locally in January 2019. This measurement is tied to one monitoring site and one year. It is neither the same thing as the Council’s separate modelled first-floor estimate nor evidence that all parts of Blantyre exceeded the objective. (Environmental Standards Scotland, Air Quality Investigation and Improvement Report) environmental standards scotland air quality report

The Council’s 2023 progress report summarises the results of the twelve-month 2022 study. It says measured NO₂ annual means from diffusion tubes were below the 40 µg/m³ objective at all study locations, while particulate readings from the AQMesh sensor were below their respective Scottish PM₁₀ and PM₂.₅ annual-mean objectives. On that basis, the Council said an AQMA did not appear to be required “currently”. It also said the study would be submitted to Defra for review and that monitoring would continue. The wording is a period-specific regulatory conclusion, not a claim that pollution was absent or that future results could not change. (South Lanarkshire Council, Local Air Quality Management Annual Progress Report 2023) south lanarkshire air quality apr 2023

The 2024 report records Defra’s appraisal: based on the evidence submitted, the Council’s conclusions were considered acceptable, with a recommendation to continue monitoring to confirm that compliance was maintained. The report’s appendix lists roadside diffusion-tube sites at 233 and 283 Glasgow Road and 1 Hunthill Road, alongside an automatic monitoring site identified as SLC09. Its site inventory lists these diffusion tubes outside an AQMA. The associated location map contains Ordnance Survey material and is not reproduced here. This 2024 confirmation concerns the appraisal of the 2022 study; it should not be mistaken for publication of a new 2024 measurement series. (South Lanarkshire Council, Local Air Quality Management Annual Progress Report 2024) south lanarkshire air quality apr 2024 historical maps

National automatic-site record

The Scottish Air Quality Database (SAQD) provides a separate, ratified annual series for the roadside station named “South Lanarkshire Blantyre”. Its 2023 report gives an NO₂ annual mean of 18.2 µg/m³, 99.8% data capture and zero hours above 200 µg/m³. Its 2024 report gives 16.8 µg/m³, 99.6% capture and again zero hours above 200 µg/m³. Both values are below the 40 µg/m³ annual mean objective. The 1.4 µg/m³ difference describes two consecutive annual values; it is not enough to establish a long-term trend or explain the change. (Scottish Air Quality Database annual report: Blantyre 2023) (Scottish Air Quality Database annual report: Blantyre 2024) saqd annual report blantyre 2023 saqd annual report blantyre 2024

The same 2024 report lists Blantyre PM₁₀ at 9.4 µg/m³ before and 10.3 µg/m³ after its Fidas correction. Data capture was 68.9%, below the report’s 75% flagging threshold, so this PM₁₀ value is less complete than the high-capture NO₂ record. These national automatic-site results neither erase the separate 2020 diffusion-tube exceedance at 233 Glasgow Road nor measure concentrations at every home and street. The station profile identifies SLC09 as part of the Scottish Automatic Urban Network, located on the A724 at 55.793907, −4.092354, with NO₂ monitoring from 9 January 2019. Its changing hourly and 24-hour live display is not used here as an annual statistic. scottish air quality blantyre site profile Glasgow Road, Blantyre

Monitoring methods and interpretation

Automatic analysers and passive diffusion tubes answer related but different questions. The Council’s reports describe the AQMesh sensor as providing higher-resolution local measurements and use diffusion tubes at several street positions, including near relevant exposure. The 2023 report notes that the wider authority’s 2022 automatic-site averages were below objectives and lower than 2019, while also attributing a sharp 2019–20 decline partly to reduced traffic during pandemic restrictions. Those area-wide trends are context; they do not replace the separate Blantyre street-level series.

South Lanarkshire Council identifies road traffic as a major source of localised air pollution across its area. That authority-wide statement helps explain why the Glasgow Road corridor was monitored, but it does not establish that traffic was the only source of any measured concentration in Blantyre. No causal estimate of the contribution from individual roads, vehicles, buildings or heating sources is made here. Bus services in Blantyre Glasgow Road, Blantyre