draft Air Quality

The UK Government has set a requirement that each local authority must develop and implement an Air Quality Strategy by the end of 2023, regardless of whether they have declared an Air Quality Management Area.

Wirral Air Quality Strategy 2024-2028 was approved by the Environment, Climate Emergency and Transport Committee in December 2023.  It covers all wards and outlines the work that the council will undertake to support the government's long-term air quality goals, including a steep percentage reduction to population exposure to particulate matter (PM2.5). The strategy will prioritise the actions that will be taken to achieve the overall aim and objectives.

The implementation of this strategy will support the vision of the Wirral Plan 2021-2026, which focuses on making the borough a more equitable and fairer place to live, work, and visit, reducing inequalities across Wirral. 

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Our Wirral Joint Strategic Needs Assessment on Air Quality was recently updated and recognised that individuals most susceptible to negative health impacts of air pollution exposure are likely to be among the most vulnerable people in society, in some cases with limited power to alter social circumstances or individual-level risk. Taking measures to improve air quality will have positive health benefits, helping to reduce health inequalities across the borough

Wirral Joint Strategic Needs Assessment on Air Quality 2022

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•  Clean Air Strategy 2019 - GOV.UK (www.gov.uk)

• National Air Quality Strategy: Framework for Local Authority Delivery (2023)

• Environment Improvement Plan (2023)

Link to out inhouse maps that Robs working on

UK Emissions Interactive Map (energysecurity.gov.uk)

Nitrogen dioxide (NO₂) is a gas made up of nitrogen and oxygen, it is a red brown colour, but it cannot be seen in the air, as it is diluted.   It is formed alongside nitric oxide (NO) during combustion.  The two gases are referred to together as nitrogen oxides (NOx).

NO2 can also be a ‘pre-cursor’ pollutant, as it can react in sunlight to form ground level Ozone.

Key Sources of Nitrogen Dioxide

NO₂ is formed during combustion processes, including the burning of petrol or diesel in a vehicle engine, or the burning of fossil fuels and wood for heat and energy.    

Further Reading

Nitrogen dioxide (NO2) - GOV.UK (www.gov.uk)

Particulate Matter (PM) is a term used to describe a mixture of solid and liquid particles of varying size, shape, and composition.  There are both natural and human made sources of PM.  Some of these particles are emitted directly (e.g through burning of wood and coal) and others are formed in the atmosphere through chemical reactions. 

PM is classified according to size in microns (µm).   The current National Objectives and Fine Particulate Matter targets for England focuses on:

• PM10 - where particles are less than 10 micrometres in diameter and
• 5 – where particles are less than 2.5 micrometres in diameter (PM2.5).

Particles larger than 10 µm are mainly deposited in the nose or throat, whereas particles smaller than 10 µm can be drawn deeper into the lung. A small proportion of ultrafine particulates can cross into the blood stream and reach other organs.

“Primary” PM is emitted directly as particles (for example, soot or dust) and “secondary” PM is formed in the atmosphere from reactions between other pollutants (for example ammonia or Non-Methane Volatile Organic Compounds (NMVOC’s)).

PM can be emitted by:

• natural processes, such as forest fires, and
• human activities, such as the combustion of fuels. 

Key Sources of Particulate Matter

• Road transport from burning fuels or lubricants used up in the engine; tyres and brakes wear; and from road dust.
• Industrial processes
• Domestic wood burning

Further Reading

Emissions of air pollutants in the UK – Particulate matter (PM10 and PM2.5) - GOV.UK (www.gov.uk)

Ozone is naturally occurring in the stratosphere, where it forms a protective layer shielding us from the sun’s radiation. However, is can also be formed at ground level, where can have adverse effects on human health and the environment. Ozone can also react with other chemicals in the air to form particulate matter, or smog.

Key Sources of Ozone

Ozone is formed through numerous chemical reactions in the atmosphere.  There are no major emission sources of ozone itself.  Ground level Ozone can be formed from reactions between nitrogen oxides (NOx), methane, volatile organic compounds (VOCs) and sunlight

Further reading

2112200932_Ozone_in_the_UK_Recent_Trends_and_Future_Projections.pdf (defra.gov.uk)

These are gases that can be emitted from both natural and human made sources.   They can combine with NOX to form ground level ozone.

Key Sources of VOC’s

• Naturally emitted from vegetation
• Emitted from human made sources including paints, aerosols, disinfectants, air fresheners.

Further Reading

2006240803_Non_Methane_Volatile_Organic_Compounds_in_the_UK.pdf (defra.gov.uk)

Ammonia is a colourless, reactive gas that is lighter than air, which dissolves readily in water.  It has a strong smell, similar to urine

Key Sources of Ammonia

• Naturally emitted at low levels throughout the environment, released from the breakdown of organic waste matter.
• Human made sources include agriculture (spreading of manures, slurry and fertilisers), industrial processes and emissions from petrol vehicles fitted with catalytic converters.

Further Reading

Ammonia: general information - GOV.UK (www.gov.uk)

Sulphur dioxide (SO₂) is a colourless, corrosive, acidic gas.  

Key Sources of Sulphur Dioxide

SO₂ can be emitted both by natural processes, such as forest fires, and as a result of human activities, such as the combustion of fuels.

Further Reading

Emissions of air pollutants in the UK – Sulphur dioxide (SO2) - GOV.UK (www.gov.uk)

We measure air quality using both passive diffusion tubes and automatic monitoring stations.  The results of our monitoring are published each year within our Air Quality Annual Status Report. 

We currently have fifty-eight monitoring locations across Wirral.  All these sites monitor for nitrogen dioxide levels and one site also monitors for particulate matter.  In addition to these monitoring sites, we also have five ‘indicative’ monitoring sites, which monitor both Nitrogen Dioxide and Particulate Matter level.  The results of our monitoring show that no breaches of National air quality objectives and standards have been identified in Wirral.  

Passive diffusion tube Monitoring

Diffusion tubes passively absorb the pollutant to which they are exposed.  A tube is installed at the monitoring site and left in place for four weeks.  It is then collected, sealed, and sent to a laboratory for analysis, using nationally agreed procedures.  The data is usually gathered at the same location for 12 months and then the monthly results are calculated to produce a single annual mean figure for the level of pollution at the site.   Diffusion tubes are useful for providing longer term measurements and observing trends in pollution concentrations, but it is not possible to examine daily or weekly fluctuations. 

Real Time Monitoring Stations

Automatic Urban and Rural Network (AURN)

Wirral has two AURN monitoring stations located within its boundaries. These monitors use a chemiluminescent analyser to continuously monitor NO₂ concentrations, this is the reference method for NO₂ monitoring specified in EU directives and is based on the chemiluminescent reaction between NO and O₃.  These monitors provide high resolution hourly measurements, and the results are available to the public online.

‘Indicative’ Real Time Monitors

Wirral has five ‘indicative’ real time monitors across Wirral.  These monitors do not use a monitoring technique that is the same or equivalent to the reference method for monitor of NO₂ or Particulate matter*.  The results cannot be used for reporting purposes to DEFRA but they can be used as supplementary information and an indicator for pollution levels.

* The reference method for Nitrogen Dioxide monitoring is a chemiluminescent analyser to continuously monitor NO₂ concentrations, this is the reference method for NO₂ monitoring specified in EU directives and is based on the chemiluminescent reaction between NO and O₃.  The reference method for particulate matter monitoring is gravimetric monitoring which pass air through a filter which is weighed before and after sampling. The PM₁₀ or PM_2.5 concentration can then be calculated as the increase in mass of the filter divided by the volume of the sample expressed to ambient conditions). 

• Wirral Annual Status Report

• Tranmere AURN

• Birkenhead AURN

Wirral 2024 Air Quality Annual Status Report (ASR)

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National Air Quality Objectives and Local Air Quality Management requirements.

Local Authorities have a duty under the Environment Act 1995 (as amended by the Environment Act 2021 and other regulations) to review and assess the local air quality within their areas, against a set of health-based air quality objectives for several specific air pollutants.  The Air Quality (England) Regulations 2000 (as amended) brought these objectives and limit levels into law.

If any areas within their boundary are found where pollutants exceed the objectives, local authorities are required to declare an Air Quality Management Area (AQMA) and to prepare an Air Quality Action Plan (AQAP) setting out the measures they intend to introduce to reduce concentrations of air pollutants, in pursuit of achieving the objectives.  Air pollution monitoring in Wirral has shown that no exceedances of the air quality objectives have been identified. 

Further Reading

• UK Air Quality Limits

• England Fine Particulate Matter Targets - Defra, UK

Global Air Quality Guideline Concentrations

In 2021, the World Health Organisation (WHO) updated its health-based air quality guideline concentrations, due to a much stronger body of evidence showing how air pollution affects health at lower concentrations.

The guidelines focus on “classical pollutants”, specifically particulate matter (PM_2.5 and PM₁₀), ozone (O₃), nitrogen dioxide (NO₂), sulphur dioxide (SO₂) and carbon monoxide (CO).   These WHO guideline concentrations are lower than those required by the UK national objective levels.

Further Reading

• WHO Global Air Quality Guidelines

Air Quality Mapping

Link to out inhouse maps that Robs working on

UK Emissions Interactive Map (energysecurity.gov.uk)

Air pollution is the biggest environmental risk to health.  It affects us all. It has negative effects on health throughout the life course, from pre-birth to old age.

• Short term: exacerbations in respiratory conditions (e.g. asthma and chronic obstructive pulmonary disease – COPD)

• Long term: respiratory, cardiovascular disease, cancer, foetal development, depression, dementia, diabetes

(image from Chief Medical Officer Report on AQ 2022)

Health Inequalities

Although air pollution can be harmful to everyone, the most susceptible to the effects of air pollution are typically the young, the old, and those with pre-existing health conditions.  It also particularly affects people living in more densely populated and polluted areas, which are often areas of higher deprivation, widening health inequalities (https://www.gov.uk/government/publications/health-matters-air-pollution).

Further Reading

• Chief Medical Officers Annual Report 2022. Air Quality

• Health Matters: air pollution

• Every Breath We Take. The lifelong Impact of Air Pollution

• OHID Public Health Profiles – Air Quality

• Air Quality Hub

• NICE Air Pollution: Outdoor Air Quality and Health

Air quality and climate change are inextricably related. Many common air pollutants are also greenhouse gases and therefore reducing air pollution will lessen the warming effect on our climate. Poor air quality and climate change have a direct impact on the health and wellbeing of both humans and the natural environment.

Further reading

• Air Quality and Climate Change

• WHO Climate Change Mitigation, Air Quality and Health

The recent Chief Medical Officer (CMO) report on Air Quality (2022) states that people spend a substantial part of their day indoors as for most people, work, study, shopping and leisure activities all occur indoors. Indoor air therefore dominates the air that people breathe in a typical day.

Outdoor air pollution can move into many indoor spaces, so reducing outdoor air pollution is important for indoor air quality, but there are also sources of pollution formed within the indoor environment.   

The CMO’s report acknowledges that there has been extensive research on outdoor air quality, but exposure to air pollution indoors has not been researched as thoroughly.    

Indoors Sources of Pollution

• NOx from combustion processes, mostly from solid-fuel burning stoves or cooking on gas hobs.

• Primary PM sources from activities such as cooking and combustion processes, including wood burning.

• VOCs from chemicals used in household objects such as personal care products, cleaning products, paints, glues and aerosols and in the fabric of the building.

• ‘natural’ pollutants, including moulds, which are more common in buildings that are not as well designed or maintained.

• Carbon monoxide (CO), from poorly maintained gas boilers and solid fuel appliances.

• Asbestos, which can be present in older buildings,

• Radon from the ground.

Further Reading

• NICE guidelines. Indoor Air Quality at Home

• Air Quality Expert Group - Indoor_Air_Quality_Report_Final.pdf (defra.gov.uk)

• Chief Medical Officer’s annual report 2022: air pollution - GOV.UK (www.gov.uk)

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