2 Air Quality
2.1 Policy Overview
• National
NPPF Chapter 14 - Meeting the challenge of climate change, flooding and coastal change
NPPF Chapter 15 - Conserving and enhancing the natural environment
Planning Practice Guidance Air Quality (2021)
DEFRA Clean Air Strategy (2019)
• Regional
London Plan Policy SI 1 Improving air quality
London Plan Policy D13 Agent of Change
Air Quality Neutral London Plan Guidance
Air Quality Positive London Plan Guidance
Non-Road Mobile Machinery (NRMM)
• Local
City Plan Policy 32 Air Quality.
City Plan Policy 29 Freight and servicing
Air Quality Action Plan
Freight, Servicing and Deliveries Strategy and Action Plan
Code of Construction Practice
Westminster Guidelines for Kitchen Extract Ventilation Systems (2021)
2.2 Introduction and Guidance
2.2.1
Background
Westminster City Council is dedicated to ensuring clean, breathable air across the city, aligning with our vision of a Fairer Westminster. As one of the city’s top environmental concerns, air pollution affects the health and wellbeing of our residents, as well as Westminster’s natural and built environment. Addressing these impacts requires a multi-faceted approach, with the council taking active steps to reduce pollution and aiming to achieve World Health Organisations air quality guideline levels by 2040. Policy SI 1 Improving Air Quality of the London Plan provides the most up-to-date policy requirements with regard to air quality.
Our emerging Air Quality Action Plan for 2025-2030 will employ an evidence-based approach to tackling pollution locally and to reduce the impact of pollution that already exists, integrating Policy 32 of the City Plan. This policy requires certain developments to adopt an ‘Air Quality Neutral’ or ‘Air Quality Positive’ approach, and mandates air quality assessments to ensure improvements without transferring pollution to other areas. In addition, the Healthy Streets approach supports the development of infrastructure that benefits public health while reducing pollution. The council’s proactive planning and policies reflect our commitment to a healthier, more sustainable future for our residents.
Air pollutants (including NOx, and Particulate Matter and Ozone amongst others) have both natural and human-caused sources. When they are released into the atmosphere, they undergo a range of chemical reactions that can has a detrimental impact on both public health, nature and the built environment.
Road transport has traditionally been the largest source of pollution in Westminster, but emissions from commercial buildings are now predicted to account in 2025 for a larger share of approximately 67% NOx, 40% PM10 (commercial heat and power & commercial cooking) and 70% PM2.5 (commercial heat and power & commercial cooking). Based on the current trajectory, for PM10, construction/ demolition dust could account for 28% in 2025, reducing marginally to 26% by 2040. There is a need for developing effective strategies to address this issue.
Road transport remains the second-largest source of pollutants with where it is predicted that in 2025 road transport will account for approximately 20% of NOx emissions, 16% PM10 Emissions and 14% of PM2.5 emissions. Whilst NOx emissions are expected to decline over time, particulate matter continues to be a persistent issue.
While many policy interventions targeting vehicle-related pollution fall outside the scope of this ESPD and the planning system, the City Plan supports clean air goals through policies such as Policy 32 (Air Quality), Policy 24 (Sustainable Transport), Policy 25 (Walking and Cycling), Policy 26 (Public Transport Infrastructure), Policy 27 (Parking), Policy 29 (Freight and Servicing), and Policy 30 (Technological Innovation in Transport).
Westminster’s Freight, Servicing and Deliveries Strategy, Air Quality Action Plan, Electric Vehicle Charging Infrastructure Strategy, and Code of Construction Practice also contribute to these goals. Measures like the diesel parking surcharge and regional interventions such as the Ultra Low Emission Zone (ULEZ) have already helped improve air quality.
Westminster’s current Air Quality Action Plan (up to 2024) and the forthcoming 2025-2029 plan, alongside the broader Sustainable Transport Strategy currently in development (as of late 2024), will outline the council’s ongoing efforts to reduce transport emissions.
Industrial and commercial activities have become the primary source of pollution in Westminster. These activities include the burning of fossil fuels for heating and power in industrial and commercial buildings, as
well as emissions from non-road mobile machinery, such as construction equipment and diesel back-up generators. These sources emit pollutants like nitrogen oxides (NOx) and particulate matter (PM). Another significant contributor to pollution is commercial cooking, where restaurants and commercial kitchens, particularly those using gas equipment, release pollutants like PM2.5.
The City Plan's Energy and Retrofitting sections, along with this ESPD, outline strategies to address these emissions. These strategies involve designing and retrofitting buildings to reduce carbon and methane emissions (another potent greenhouse gas), improve energy efficiency, and increase the use of renewable energy. Key interventions include aiming to electrify buildings, transition to electric cooking equipment, and connect buildings to low-carbon decentralised energy networks. Additionally, the City Plan includes a netzero carbon target for major developments, ensuring that new buildings contribute to cleaner air and reduced greenhouse gas emissions.
Emissions from demolition and construction work are also key sources of particulate matter and can cause highly localised spikes in pollution. Where all or part of the existing building can be retained and demolition can be avoided, this will avoid dust and emissions from demolition as well as help conserve resources, reduce upfront embodied carbon emissions and minimise waste. Further information on Sustainable Design Principles and the council’s preference to consider retaining buildings first before proceeding with plans for demolition are set out within the ESPD sections on Sustainable Design and Retrofit.
Westminster requires Whole Life Carbon (WLC) Assessments for applications referable to the Mayor of London and major developments2 involving substantial demolition3. The approach to undertaking a WLC assessment should follow the latest RICS Professional Standard on Whole Life Carbon Assessment, 2nd edition. The approach to considering whether a building should be retained and retrofitted, or demolished and re-built should follow the considerations set out in Section 10.3 of this document which incorporate the London Plan Guidance on Whole Life Carbon Assessments and Circular Economy Statements. In following this approach, Westminster requires applicants to consider the retrofit or reuse of any existing built structures before embarking on the design of a new structure or building. See the ESPD section on Sustainable Design for more details.
Where demolition does take place, City Plan Policy 33 relating to Local Environmental Impacts, and the council’s Code of Construction Practice, requires developers to provide mitigation measures for dust and air pollution during the demolition and construction process. The chapter in this ESPD on Local Environmental Impacts provides further details.
Green Infrastructure can play a part in the improvement of air quality, please see the Green Infrastructure chapter for further guidance.
The behaviour of our communities also has an impact on pollution levels and behaviour change will play a key part in tackling the issue. Further information of what residents, visitors and businesses can do to help and also to reduce their own personal exposure can be found in the supporting guidance associated with the Air Quality Action Plan.
2 Development of 150 residential units or more and/or development over 30 metres in height referable to the Mayor. Major development is greater than or equal to 10 residential units; or 0.5 hectares site area (residential) or 1 hectare (nonresidential); or gross floorspace of 1,000 sq m (GIA).
3 Substantial demolition is defined as being the demolition of more than 50% of the floor slabs and substructure of any preexisting building.
It is important to note that although carbon dioxide and methane are not considered to be air pollutants, they are greenhouse gases. There are distinct synergies between carbon emissions reduction and air quality improvements, and actions to realise these co-benefits will be expected as part of development proposals.
2.2.2 Key Considerations
AIR QUALITY NEUTRAL
The London Plan Policy SI1B2a postulates that all development proposals must be at least Air Quality Neutral. It sets out minimum requirements for developments in the form of emissions benchmarks that must be met and technical requirements for the installation or operation of some types of combustion equipment. Detailed technical requirements for Air Quality Neutral, including how to undertake the benchmarking calculation, are set out in London Plan Guidance published by the GLA. Developers are required to follow this guidance for applications in Westminster.
Developments that do not include additional emissions sources are assumed to be Air Quality Neutral and to meet the Air Quality Neutral benchmarks without performing the calculation. In these cases, applicants should set out clearly in the Planning Statement or covering letter why they are excluded from Air Quality Neutral, including references to the relevant plans or design documents. As set out in the London Plan Guidance, phased developments may need to revisit the Air Quality Neutral calculation as detailed applications are brought forward for each phase.
AIR QUALITY POSITIVE
Air Quality Positive should be applied to masterplans and development briefs for large-scale development proposals subject to an Environmental Impact Assessment. In this context, ‘large scale development’ refers to planning applications that are referable to the Mayor under the following categories of The Town and Country Planning (Mayor of London) Order 2008:
• Category 1A
• Category 1B
• Category 2C(1)(a)-(f)
• Category 2C(2)
• Category 2C(3)
• Category 2D
The Air Quality Positive approach should inform a project from the concept stage, before detailed plans are developed. Pre-application engagement is strongly recommended. The scheme’s Air Quality Positive statement should set out matters which may be secured by planning condition or legal agreement, and issues or constraints for subordinate developments.
COMMERCIAL COOKING
Enhancing existing kitchen ventilation systems, upgrading filtration and ensuring regular maintenance can effectively capture pollutants such as PM2.5, nitrogen dioxide (NO2), and volatile organic compounds (VOCs). This approach complements the use of induction cooking and ESP systems, offering a quicker and more cost-effective solution.
Induction Cooking: Transitioning commercial kitchens to electric, ideally induction cooking is a key climate and air pollution friendly solution. Induction hobs offer a cleaner and more energy-efficient alternative to
gas-powered stoves. This method reduces indoor air pollution by eliminating the combustion of fossil fuels, thus lowering emissions of nitrogen oxides (NOx), carbon dioxide (CO2), and methane. Additionally, induction cooking is highly energy-efficient, using up to 95% of energy compared to just 50% with gas.
Electrostatic Precipitator (ESP) Filtration Systems: ESP systems are designed to improve air quality by targeting the removal of fine particles (PM2.5), grease, smoke, and other pollutants produced during commercial cooking. Using an electrostatic charge to capture particles in the airstream, ESPs can remove up to 98% of pollutants from kitchen exhausts. While they offer a less invasive solution than transitioning to induction cooking, they still involve operational disruption, as the kitchen’s extraction system must be designed to accommodate an ESP. This includes adjustments to fan speeds to achieve the required air changes and addressing potential space constraints, particularly in smaller kitchens typical of Westminster. Although ESP systems require a significant upfront investment, they tend to be more cost-effective over the long term due to lower maintenance requirements.
Applications are expected to refer to Westminster’s guidance relating to ‘Prevention of odour and fume nuisance from commercial kitchen exhaust systems’.
2.3 Development Requirements
2.3.1 Information
AIR QUALITY ASSESSMENT:
Air Quality Assessments are required for all developments in Westminster that meet the following criteria:
• Major developments4;
• Proposals that include potentially air pollution generating uses or combustion-based technologies;
• Proposals incorporating sensitive uses5; and
• All residential developments within Air Quality Focus Areas
- Air Quality Focus Areas in Westminster
The purpose of an Air Quality Assessment is to understand, and where possible, assist the developer in avoiding detrimental local impacts of air pollution arising from a development. It is not permitted to assume that a development will have no local impacts just because it has met the Air Quality Neutral benchmarks.
4 In accordance with the City Plan, development greater than or equal to: 10 residential units; or 0.5 hectares site area (residential) or 1 hectare (non-residential); or gross floorspace of 1,000 sq m (GIA).
5 Sensitive uses include many types of social and community infrastructure, including schools, hospitals and nursery facilities, as well as types of specialist housing such as elderly housing and care homes.
Figure 1
In addition to the technical requirements set out below applicants are required to show how their proposals are consistent with relevant policies in the Westminster Air Quality Action Plan. Table 1 below outlines the expected content of Air Quality Assessments submitted as part of a planning application.
Table 1 Content of air quality assessments
Category Notes
Introduction and Description of Development
Authors name and qualifications. Date of assessment
Maps / Plans included
Photo of site and surroundings
Relevant guidance / Standards referenced
• Ensure consistency with submitted application description
• Recent date / Appropriate level of competency of report author
• Note whether development is within an AQFA
• Should include any features of significance, such as local sources of pollution, existing receptors or other key constraints.
• E.g. EPUK guidance; London Councils guidance
For the operational assessment
Evidenced statement on why a detailed AQ assessment required
Baseline assessment
Modelling methodology
• Reference should be made to the criteria listed above.
• This evidence should also inform the scope of the assessment.
• Relevant data used from appropriate monitoring stations, diffusion tubes / Defra background maps, LAEI
• The choice of data sources used, and appropriate baseline year should be justified.
• Where short term diffusion tube campaigns are used to support the baseline assessment annualization calculations must be shown to be in accordance with DEFRA guidance TG(22).
• Inputs to be appropriate to the development under consideration.
• Transport, building and energy centre emissions from the new development should be cross referenced to the relevant plans and documents in the application. Any assumptions or scaling factors should be described and justified.
• Building emissions for industrial or commercial uses should include emissions from the use, e.g. commercial cooking.
Receptors evaluated
• Emissions data for existing sources should be as robust as possible and any assumptions made described and justified.
• Emissions factors and parameters should be supported by reference to technical data sheets or published tools (such as the DEFRA Emissions Factor Toolkit).
• Technical modelling parameters (such as surface roughness or Monin-Obukhov Length) should normally be the defaults for large urban centres. Any deviations should be justified.
• The source for background concentrations and meteorological data should be clearly stated
• Chosen specified receptor location, both within the development and in the surrounding should be chosen to be representative of the most affected locations and the most sensitive users.
• An assessment should be made of how many people or properties each specified receptor is representative of.
• In addition, isopleth maps should be prepared showing the overall distribution of pollution in and around the development.
Pollutants assessed
Model verification
For construction assessment
Construction traffic inclusion
Dust risk assessment
Significance criteria
Mitigation
Interpretation
• Appropriate to the pollutant source e.g. NO2 and PM for most road traffic and building emission assessments. Additional pollutants may need to be considered for some industrial and commercial uses.
• Any model verification must be undertaken in accordance with the procedures set out in DEFRA’s technical guidance TG (22).
• Steps taken to improve the model to reduce the verification factor should be set out and any remaining disparities explained.
• Reference should be made to the Westminster Code of Construction Practice, section 5.7 of this guidance and relevant guidance from the GLA.
Conclusion
• The conclusion should set out the expected impacts and concentrations post completion.
• Any design features or parameters which are critical to achieving the predicted impacts should be clearly laid out so that they can be secured by condition or other agreement.
• Professional judgement on the acceptability of the impacts remains with the planning authority.
Where required or appropriate, planning conditions will be used to ensure that the final development is built in accordance with the parameters used in the Air Quality Assessment.
AIR QUALITY NEUTRAL
A reassessment of compliance with the Air Quality Neutral will normally be required as part of any application for amendments to a planning consent that affects any of the following:
• energy strategy
• the proposed type or number of power and/or heating appliances
• transport strategy and/or travel plan
• number of parking spaces
• parking management plan
• number of residential units
• floorspace assigned to non-residential use classes.
The reassessment should be proportionate and limited to the extent of the amendments. For example, a change to the number of car parking spaces would not need a reassessment of building emissions.
A change that would unambiguously reduce emissions, such as replacing planned domestic boilers with heat pumps, or removing car parking may be allowed on that basis without reassessment at the discretion of the local planning authority.
Where required or appropriate, planning conditions will be used to ensure that the final development is built in accordance with the parameters used to inform the Air Quality Neutral calculation.
Developments that are unable to meet the Air Quality Neutral benchmarks should seek to agree appropriate mitigation measures, which may be secured by legal agreement. If appropriate mitigation measures cannot be identified, Westminster will secure off-setting payments through legal agreements, in line with the GLA guidance.
AIR QUALITY POSITIVE
An Air Quality Positive Statement should be submitted as part of the Environment Impact Aassesment (EIA) and updated as appropriate for reserved matters applications, outlining the Air Quality Positive approach taken. Where the proposal meets the above criteria for a large-scale development subject to an EIA, but does not have a masterplan or development brief, an Air Quality Positive Statement is still required.
Detailed technical requirements for Air Quality Positive, including how to prepare a compliant Air Quality Positive Statement, are set out in London Plan Guidance published by the GLA. Developers are required to follow this guidance for applications in Westminster.
Applicants are reminded that, in order to produce a compliant Air Quality Positive Statement, initial phases of the work on air quality should be commenced before any designs are finalised. Applicants are strongly recommended to discuss Air Quality Positive at the pre-application stage.
Applications that meet the threshold for Air Quality Positive but are not accompanied by a compliant statement may be refused.
Among the minimum requirements for an Air Quality Positive Statements, it is expected that:
• there is a realistic mechanism to ensure the proposed measures will be secured, and
• there is a suitable implementation and monitoring plan for longer-term targets.
Planning conditions or Section 106 agreements may be used, where appropriate, to secure measures or ongoing monitoring.
Where proposed monitoring includes ambient air quality monitoring the applicant is referred to Westminster’s Air Quality Action Plan for further guidance.
2.3.2 Standards
Policy SI 1 Improving Air Quality of the London Plan sets out a requirement that all development proposals must be at least Air Quality Neutral. Development proposals in Air Quality Focus Areas or that are likely to be used by large numbers of people particularly vulnerable to poor air quality, such as children or older people should demonstrate that design measures have been used to minimise exposure.
2.4 Monitoring
City Plan Key Performance Indicator 21: Reduction of NOx and particulate matter (PM2.5 and PM10) concentration against national and regional Air Quality targets and WHO guideline level