Air Quality in Lancashire
2005

Introduction

A combined indicator of air quality for small local areas was first developed on behalf of the Office of the Deputy Prime Minister, now the Department for Communities and Local Government (DCLG) for use in the generation of the English Indices of Deprivation 2004 (ID 2004). Originally constructed on the basis of 2001 data the Air Quality Indicator was updated using 2003 information and again with the ID 2007 based on the year 2005. The Air Quality figures are published by Lower Layer Super Output Areas (LSOAs) and the complete data set for England has more than 32,000 LSOAs. Full downloads of the first two sets of data are available from the Office for National Statistics Neighbourhood Statistics website whilst the latest 2005 data can be accessed from the DCLG website. The same data covering the period 2001-2005 relating specifically to Lancashire can be obtained from our Data Download Centre.

Background to the Data and Methodology

The data underlying the Combined Air Quality Indicators are drawn from the National Atmospheric Emissions Inventory (NAEI). The NAEI compiles estimates of emissions to the atmosphere from nine principal sectors (residential, services, industry, and road transport, off road vehicles, shipping, rail, aviation, and other) and from over 140 secondary sectors. The data are of annual mean concentrations for each 1km2 grid cell centroid in the UK. The Air Quality Indicator uses NAEI measures of emission of four main pollutants for which there are reliable small area level measures and clearly defined annual standard values, namely: benzene, nitrogen dioxide, sulphuric dioxide and particulates (PM10). (Background information on each of these four pollutants is contained at the end of this paper). Modelled estimates of annual mean concentrations for each of the pollutants in each LSOA were derived. These values were then compared with World Health Organisation/DEFRA guidelines or "standard values" for pollutants that represent "safe" concentrations to arrive at a quality score in which values greater than 1.0 are deemed to represent an unsafe concentration of the pollutant in question. Values of less than 1.0 indicate that the pollutant is below the objective set and thus "safe". The Combined Air Quality figure which represents the overall quality score or ratio for each LSOA is derived simply by the addition of the scores for each of the four pollutants. A higher value implies a poorer overall air quality though there is no stated value above which the Combined Air Quality Indicator itself is said to indicate an unsafe concentration of pollutants.

National Context

Lancashire's Highest Air Quality?

Concern about air pollution in the UK is of long standing. Complaints were recorded as far back as the 13th century when the use of coal in London was prohibited on the ground that it was prejudicial to health. During the Industrial Revolution sulphurous and smoky winter smog pollution in urban areas became a significant problem arising from the burning of coal for both domestic and industrial purposes. After the Clean Air Acts of 1956 and 1968 emissions of sulphur dioxide and smoke in the UK fell dramatically and with cleaner fuel technologies continues to do so. Today, the main threat to clean air is posed by traffic emissions which continue to rise with the growth in vehicle numbers. Petrol and diesel vehicle engines emit a wide variety of pollutants, principally carbon monoxide (CO), oxides of nitrogen (NO_x), volatile organic compounds (VOCs) and particulates. In addition, photochemical reactions resulting from the action of sunlight on nitrogen dioxide (NO₂) and VOCs from vehicles leads to the formation of ozone, a secondary pollutant which impacts in rural areas often far from the original point of emission.

According to the latest 2005 estimates, across the whole of England combined air quality scores for LSOAs vary within a range of 0.52 (best) and 2.54 (poorest) – a difference of more than five-fold. The very poorest air quality with LSOA scores of 2.3 or greater are recorded in parts of the City Of London and the central London boroughs of Camden, Westminster, Lambeth, Southwark, Islington, Hackney and Tower Hamlets. Outside of London the poorest LSOA air quality scores are to be found in parts of the metropolitan districts of Rotherham and Sheffield in South Yorkshire and parts of Birmingham and Sandwell in the West Midlands where presumably they are attributable in part to the importance of metal processing and other high energy use industries as well as traffic pollution in these areas. However, as a more general problem poor air quality is clearly an issue that faces the central areas of all the major conurbations and larger city areas. Within the North West of England the poorest placed LSOAs for air quality are to be found in Salford (with scores of 1.85). Conversely, it is not surprising that LSOAs with best air quality scores are typically to be found in the more remote rural and peripheral locations of England. These are to be found across parts of Cumbria (Allerdale has the distinction of an LSOA with England's very best score for air quality of 0.52) and Northumberland across the North of England where recorded air quality scores are mainly less than 0.6, and in Devon and Cornwall in the South West of England.

Lancashire Results

The top and bottom ranked Lancashire LSOAs in terms of their Combined Air Quality Indicator scores are shown in Table 1 whilst Figure 1 presents the distribution of the LSOA air quality scores across the whole of the Lancashire sub-region.

The average Lancashire LSOA has an air quality indicator of 1.01 which is notably better than the figure for England, whilst the highest recorded score in Lancashire (1.39) is significantly below the worst level recorded in the country. No areas of Lancashire experience air pollution levels on anything like those recorded in the centres of the major conurbations and other larger cities. There are some parts of the sub-region where the figures are not encouraging but the Combined Air Quality Indicator reveals no Lancashire LSOA in the worst 15% of results for the whole of England. Indeed, nearly nine in every ten of Lancashire's LSOAs are ranked within the best 50% of England for air quality and 260 of the sub-region's LSOAs (27% of the total) sit within the best 10% in England.

The areas in Lancashire with the very best air quality are based largely within the Bowland and Lune Valley areas of the county but this is largely a matter of degree as additionally air quality across coastal parts of the sub-region in Lancaster, Wyre and West Lancashire together with upland parts of Pendle also score highly. Not unexpectedly, in the main, rural areas enjoy higher air quality than urban areas (Figure 1)

Figure 1 Combined Air Quality Indicator Scores, 2005

Source Department of Communities and Local Government - Combined Air Quality Indicators, 2005

Most urban areas in Lancashire suffer to some degree from relatively poor air quality though it is much less of an issue in the coastal towns of Lancaster/Morecambe, Fleetwood, Lytham St Annes and even Blackpool, presumably due in part to the direction of the prevailing winds. The worst air quality figures are to be found in a number of LSOAs in South Ribble and Chorley within the Bamber Bridge and Clayton-le-Wood North wards. The urbanised nature of much of this area together with industrial development, motorway through-traffic and the intersections of the M6/M61/M65 appear to combine to produce a significant local concentration of poor air quality. A significant concentration of poor air quality is similarly to be found among a number of LSOAs in Blackburn, most notably in Audley, Queen's Par and Shear Brow. Smaller pockets of degraded air quality can be found in LSOAs in Chorley, Prestron and Skelmersdale and across East Lancashire from Darwen through Accrington/Oswaldtwistle through to Burnley and Nelson.

There is no stated value above which the Combined Air Quality figures are said to indicate an unsafe concentration of pollutants. This is not the case however for each of the four individual pollutants for which ratios of one or above indicate unsafe concentrations. Overall, particulates account for about 48% of the overall Lancashire air quality indicator score whilst nitrogen dioxide is responsible for about 42%. The contribution of sulphur dioxide and benzene is relatively small accounting for 6% and 4% respectively of the overall index. Nationally, nitrogen dioxide is the only pollutant to record ratios in some LSOAs at or above the value of one. There are some 770 LSOAs (2.4% of the total with this characteristic though all but a handful were in central London boroughs. The highest scores for nitrogen dioxide in Lancashire (0.70) were to be found in the same Chorley and South Ribble areas referred to above. In terms of particulates, now the largest single contributor to the combined index, the maximum ratio (0.57) was again to be found in the same few LSOAs but the higher scores had a much wider footprint over all the central and east Lancashire districts, closely paralleling the motorway routes.

Change in Air Quality

With Combined Air Quality Indicator scores extending over the years 2001 to 2005 it is possible to provide some measure of the change in air quality over time. The period is probably too short to distinguish many real or significant changes at the LSOA level, especially given that the scores for these small areas are modelled measures and too much credence should not be given to such detail. However, on balance air quality overall across Lancashire does seem to have improved (Figure 2).

Figure 2 Change in Combined Air Quality Indicator Scores, 2001-2005

Source ONS/Department of Communities and Local Government - Combined Air Quality Indicators, 2001-2005

Out of the total 940 LSOAs, 679 or nearly three-quarters recorded either no change in air quality score or an improvement. The biggest air quality improvements appear to have been within rural areas generally but most especially in those areas popular as dormitory locations and which are also closely associated with higher average household incomes. This improvement has been associated with significant falls in nitrogen dioxide scores. Indeed every single LSOA in Lancashire has seen some reduction in nitrogen dioxide – in some instances by more than a half. The share of this pollutant in the combined index across Lancashire has fallen from 58% of the overall figure in 2001 to 42% in 2005, probably reflecting improved vehicle emissions. Against this drift, however, there has been some apparent deterioration in air quality scores, not exclusively, but mainly in the urban areas of Blackpool and Lancaster/Morecambe Although both these areas continue enjoy higher air quality than many other Lancashire urban areas, in comparative terms nitrogen dioxide emissions appear to have fallen much less than in many other parts of the sub-region. A cluster of LSOAs in Pendle, mainly within Nelson/Colne also appear to have seen some deterioration in air quality.

In the case of particulates, every Lancashire LSOA has seen some increase in this particular pollutant, in some instances by over 50% such that its share in the combined index has risen from a third in 2001 to 48% in 2005. Increased particulates were particularly significant within the urban areas, notably across much of central Lancashire but also across both East Lancashire as well as parts of the Fylde Coast. In the case of the two remaining pollutants, which constitute about 10% of the combined indicator, continued substantial falls were evident across most areas in sulphur dioxide emissions but benzene values recorded, in many cases, very significant percentage increases, albeit from very low levels.

Background Information on the Four Pollutants

Nitrogen Dioxide

The term 'nitrogen oxides' (NO_x) is used to refer to two gases – nitric oxide (NO), which is a colourless, odourless gas, and nitrogen dioxide (NO₂) which is a reddish-brown gas with a pungent odour. Nitrogen oxides contribute to acid rain, depletion of the ozone layer and have detrimental effects on health. They are also greenhouse gases.

Major man-made releases of nitrogen oxides are primarily from fuel combustion, biomass burning and some production processes, but there are also minor natural sources such as natural fires and biological processes in soils and waters. Nitrogen oxides from combustion processes consist of nitric oxide at the point of release, but this is gradually converted to nitrogen dioxide by reaction with other gases in the atmosphere. The major source of NO_x released to the atmosphere in the UK is road transport emissions, contributing 46% of the national total. Major road networks and urban areas have the highest levels of nitrogen dioxide (generally in the range 10-45ppb but can be as high as 200ppb) and is lower in rural areas but it is present in the air over most of England and Wales.

There are no clear trends in the levels of nitrogen dioxide in the air since 1976, although the annual average concentrations have remained fairly stable for the last 12 years. This is partly because while nitrogen dioxide emissions from industrial sources have fallen, road transport emissions have risen. The monitoring sites at which the highest nitrogen dioxide concentrations are measured are situated at busy roadside locations.

Particulate Matter

Particulate matter refers to tiny particles suspended in the air. They are made up of many different substances including soot (carbon), metals and inorganic salts such as sea salt. They vary in size and shape and are often split and reported as total particulates or PM10 (particulates with diameter less than or equal to 10 micrometres.

Soot particles are released into the air from combustion processes like coal burning, motor vehicle use, waste incineration and other industrial processes. Other types of particulates are created by construction and quarrying and by natural phenomena such as forest fires, volcanoes and dust storms. Particulate forms of many substances find application in many types of industry. Iron and steel works, cement and lime works and the rubber industry are major users of finely divided materials in their processes. Other smaller-scale everyday uses are common such as in photocopier inks.

Particulates in the air can be difficult to control and are usually released incidentally by industrial or other human activities. Particles can stick to the surfaces of buildings resulting in blackening of the facades. They can also settle on plants and damage leaves, and for humans they may affect the heart and lungs. Particulates are often seen as one of the most critical of pollutants held to be responsible for several thousands of premature deaths in the UK each year.

In the past particulate matter emitted into the air was predominately a result of domestic and industrial coal burning, which along with sulphur dioxide led to the famous London smogs in the 1950s and early 1960s. Smoke emissions have fallen significantly as a result of the Clean Air Act eliminating domestic coal combustion in many urban areas. More recent concern has focused on particulate matter arising from the combustion of diesel in the transport sector (all road transport emits PM10, but diesel vehicles emit a greater mass of particulates per kilometre), which has been linked with harmful health effects.

Sulphur Dioxide

Sulphur dioxide (SO₂) is a man-made and naturally occurring colourless acidic gas with a penetrating, choking odour. The main source of sulphur dioxide is the burning of fossil fuels in power stations, oil refineries and other large industrial plants. The fuel and power sector is by far the largest source of sulphur dioxide, contributing 73% of the national total. Motor vehicles, domestic boilers and fires also release sulphur dioxide and it is produced naturally by active volcanoes and forest fires, and from the oxidation of other sulphur compounds.

Annual mean concentrations in most large UK cities are well below 35 ppb with typical mean values in the range of 5-15ppb. Hourly peak values can be as high as 750ppb on infrequent occasions. Natural background levels are about 2ppb.

Sulphur dioxide can irritate the eyes, and at peak environmental concentrations may increase the symptoms of those suffering from asthma or lung disease. Sulphur dioxide can also lead to direct effects on vegetation and contribute to acid rain. It is considered more harmful when particulate and other pollution concentrations are also high. Sulphur dioxide can be transported over long distances and up to a third of the deposition of sulphur in some parts of the UK may arise from continental sources. There has been a steady and substantial decline in the ambient concentrations of both sulphur dioxide since 1962. This decrease was initially achieved through controls on coal burning, introducing cleaner solid fuels, taller power station stacks and relocating power stations into rural areas. In recent years further decreases have been achieved through generating more electricity from gas and nuclear power, using low-sulphur fuels and fitting flue gas desulphurisation equipment to certain power stations.

Benzene

Benzene is both a naturally occurring and man-made chemical. It is primarily used in the manufacture of items such as dyes, detergents, plastics, fibres, pesticides, adhesives and coatings, lubricating oil additives, dry cleaning, paint and some types of rubber, and is also present in petrol.

Benzene is a carcinogen that has a direct toxic effect on genetic material. Whilst there is no safe level to which people can be exposed, the risks decrease as the cumulative exposure of an individual is reduced. It is also a VOC (Volatile Organic Compound), which can contribute to the formation of harmful ground-level ozone. The major source of benzene released to the atmosphere in the UK is road transport arising from both evaporation and exhaust emissions, contributing 40% of the national total. Other significant releases are from its production and use in the manufacture of other chemicals and from other types of fuel combustion. Natural environmental releases of benzene such as from volcanoes and forest fires are insignificant in comparison to releases from human activities. Benzene emissions have been steady decreasing, primarily due to the introduction of vehicles equipped with catalytic converters, although emissions from the domestic and industrial sectors have also been falling.

This page was compiled by Peter Kivell.

All enquiries from the press should be sent to Corporate.Communications@lancashire.gov.uk.

Any other questions about the content of this page may be sent to EconInfo@lancashire.gov.uk.

For all enquiries about the county council's services, contact the Customer Service Centre on 0845 0530000 (01772 530000) or at Enquiries@css.lancscc.gov.uk.