Air quality

Summary of emissions data per sq km for nitrogen oxides, particulates and sulphur dioxide

We have analysed the local 2022 emissions data per square kilometre for nitrogen oxides, particulates and sulphur dioxide.  These have been sourced from the National Atmospheric Emissions Inventory. Nitrogen oxides are greenhouse gases that contribute to acid rain, depletion of the ozone layer and have detrimental effects on health. High emission levels in the county are associated with urban areas and the main road networks. Particularly high local area emissions are not surprisingly found at locations of major industrial activity in the county. 

It is important to note that high levels of local emissions cannot be directly equated with local air quality at ground level. The height of an industrial chimney will be specifically regulated for the industrial processes being carried out, and the emissions will be dispersed away from the plant depending on meteorological conditions. Emissions from traffic tend to have a more direct impact on air quality at ground level.

Particulate matter refers to tiny particles suspended in the air. They include not only smoke and dust particles, but also mould and other spores and pollen. Particulates may affect the heart and lungs, and are often seen as one of the most critical of pollutants as a result of their impact on human health. 

We have analysed the separate sources of emissions from 3 sectors, and looked in particular at the road transport data. We have also calculated total and average emission values for all 14 Lancashire authorities, together with the percentage of NO_x and particulate emissions attributable to road transport sources. This is displayed in the Microsoft Power BI slide below (which can be expanded to full-screen by clicking the double-headed diagonal arrow on the right of the grey footer bar) and is available as a Microsoft Excel download at the foot of the page. The results are displayed in the Power BI report which has been extended to 5 slides. We have not provided any static maps this time, but the pdf download provides some background information.

The key findings are:

• Heidelberg Materials (formerly Hanson Cement) near Clitheroe in Ribble Valley was identified as the source of 646 tonnes of NO_x, 112 tonnes of sulphur dioxide and 24.1 tonnes of particulate matter
• In Hyndburn 205 tonnes of NO_x, 63.8 tonnes of SO₂ and 23 tonnes of particulate matter were generated from industrial sources
• In West Lancashire 205 tonnes of NO_x and 55.8 tonnes of SO₂ were generated from industrial sources
• The motorways in Chorley district were sources for 403 tonnes of NO_x and 21.3 tonnes of particulate matter
• The motorways in Lancaster district were sources for 241 tonnes of NO_x and 14 tonnes of particulate matter
• The motorways in South Ribble were sources for 147 tonnes of NO_x and high levels of particulate emissions (7.8 tonnes)
• The motorways in Preston were sources for 255 tonnes of NO_x and high levels of particulate emissions
• NO_x emissions from road transport sources were up by 5.4% from 2021 across the Lancashire-12 area
• Heysham Port was the source of over 160 tonnes of NO_x
• Warton Aerodrome is identified as a source for over 70 tonnes of NO_x
• Chemical and waste processing works on the Wyre estuary produced 47 tonnes of NO_x

The background report on emissions is in the 'Further analysis' panel at the foot of the page

Concentrations of air pollution (Defra data)

An additional source, providing a complementary indication to emissions of pollution, is the Department for Environment, Food and Rural Affairs UK Ambient Air Quality Interactive Map, which shows some of the most common pollutants which are also seen in the NAEI emissions maps but as average concentrations rather than tonnage emitted. Concentrations are given in micrograms per cubic metre of air (µgm^-3 or µg/m³). Each pollutant is shown in background or roadside concentrations. For the latter you can select a road section for which a variety of pollutant values will be displayed. This data is available for years up to 2023. Urban area and local authority boundaries can be overlaid in this facility as can the Air Quality Management Area boundaries in which Nitrogen dioxide is monitored - see the accompanying Lancashire Insight article on air quality monitoring. We are now including a new Microsoft Power BI report showing just the Lancashire-14 results. If you view this on a device with a pointer it will show the background concentration for all grid squares along with the UK minimum and maximum values and the World Health Organization recommended level as a target. 

Key points for Lancashire-14

• The average district concentrations of NO_x in Chorley, Hyndburn, South Ribble and Blackburn with Darwen were fractionally above the WHO recommended limit of 10 µgm^-3, while in Preston it was just below.
• Lancaster had the lowest average concentration of NO_x at 4.35 µgm^-3
• All districts except Lancaster had average concentrations of PM_2.5s that exceed the WHO recommended limit of 5 µgm^-3.
• Nowhere in Lancashire was the WHO limit for SO₂ exceeded.
• Nowhere in Lancashire was the official legal limit for any of the three pollutants exceeded, either at district or km² level.
• Rossendale had some of the highest concentrations of roadside pollution in Lancashire with 3 sites having levels over 20 µgm^-3 of NO₂.
• The highest roadside concentration in Lancashire was at Walton Summit in South Ribble beside the M6 but near its intersection with the M61.

Table 1: Background concentration limits for 3 pollutants

	PM2.5	NO2	SO2
WHO recommended level	5	10	40
EU/UK official limit	25	40

The second page of the report shows the roadside concentrations on a map and in a table. By selecting a road link in the table the map will zoom and pan to that link. The roadside concentration data is for a limited selection of road links in urban areas. The three pollutants we are showing are PM_2.5, PM₁₀ (particulate matter) and NO₂. Rossendale had some of the highest concentrations of roadside pollution in Lancashire. Three of these sites had concentrations of NO₂ above 20 µgm^-3, the highest being 28.49 µgm^-3. The highest roadside concentration in Lancashire was at Walton Summit in South Ribble beside the M6 but near its intersection with the M61. NO₂ levels here were just below 30 µgm^-3. Major roads which convey heavy goods vehicles and have steeper gradients tend to be most polluted.

Sulphur dioxide is not a component of road traffic pollution. It is not considered hazardous to health in small quantities and is added to some foodstuffs as a preservative. The highest concentrations of NO₂ and PM_2.5s were in Inner London where road traffic is heaviest but the highest concentrations of SO₂ were in Northern England and are associated with industrial combustion. A major natural source of SO₂ is volcanic activity. On May 31st 2024 a plume of volcanic gases which had originated in Iceland caused a spike of 1,161 µgm^-3 of SO₂ to be recorded in Edinburgh. Even this amount is not considered hazardous for indoor working. Whether this will have much impact on the annual average for 2024 in any part of the UK remains to be seen.

Summary of air quality results from the 2025 indices of deprivation

A combined indicator of air quality for small local areas was developed as part of the English Indices of Deprivation and the results are available for the 945 lower super output area level (LSOAs) in the Lancashire-14 area. The air quality indicator is now one of six indicators that contribute to the Living Environment Deprivation Domain. Four pollutants are included: NO₂, SO₂, particulates and benzene. For 2025 estimates of background pollution are compared to World Health Organization guidelines. As a consequence the results are more similar to the section above on background concentrations than for previous indices. Many urban areas in Lancashire suffer to some degree from poorer air quality than other parts of the county though it is much less of an issue in the coastal towns.

The highest recorded score in Lancashire (3.03), is considerably less than the worst level recorded in the country (5.72). Most of the higher scores are from areas within London.

Of the 12 LSOAs with the highest air quality indicator scores (above 2.84) in the Lancashire-14 area, two in West Lancashire have scores exceeding 3. These are in the Digmoor area and border the M58 motorway. The next highest (2.91) is in Preston, an area covering Red Scar and straddling the M6 motorway. The fourth highest at 2.89 is an LSOA that adjoins the first two in West Lancashire, enclosed by the M58, junction 5 on the M58 and the A577. The next 8 cover the west and south east of Chorley town centre. This pattern is entirely different from what was seen in 2019. There are 29 LSOAs with air quality indicator scores below 1.58 in Lancaster, Ribble Valley, Wyre and Pendle. They cover much of the northern part of the county, but not the Lancaster and Morecambe urban area. Those with the best scores, 1.25 or 1.29, are large LSOAs in the rural north-east of the county.

 

Page updated January 2026