The case for cycling: air quality
The case for cycling: air quality
Many sources pollute the air, but one of the main offenders is motor traffic.
This means that converting as many car trips as possible to non-polluting active travel – cycling, walking and wheeling – would undoubtedly help clean the air and, at the same time, improve people’s health through higher levels of physical activity.
The UK, UK nations and local councils would also be in with a better chance of meeting their obligations on air quality.
Harm to health and the NHS
Given the evidence, it is no wonder that the World Health Organisation (WHO) describes air pollution as a “major threat to health and climate across the globe”.
It is no wonder either that almost half of the respondents to the National Travel Attitudes Survey (NTAS), Wave 3 (England, 2020) expressed concerns over poor air quality in their immediate neighbourhood.
In the UK, human-made air pollution is linked to tens of thousands of deaths – roughly between “between 28,000 and 36,000 deaths every year”, according to government guidance.
The same guidance also says: “… between 2017 and 2025 the total cost to the NHS and social care system of air pollutants (fine particulate matter and nitrogen dioxide) […] will be £1.6 billion.”
And, with young children among the most sensitive and vulnerable groups because of their higher breathing rates, it’s especially disturbing to learn that babies in low-level pushchairs are exposed to 44% higher fine particle concentrations by the roadside than adults, with brake/tyre wear emissions dominating at ‘baby height’.
A stream of alarming findings, many of them covered in Air Quality News, shows that almost every organ in the body can be affected, in the short and long term.
Specifically, the WHO says that air pollution is strongly linked to stroke, ischaemic heart disease, chronic obstructive pulmonary disease, lung cancer and pneumonia, plus increased risk for “adverse pregnancy outcomes (i.e. low-birth weight, small for gestational age), other cancers, diabetes, cognitive impairment and neurological diseases.”
In fact, studies into air pollution and dementia are of growing concern.
Poor air quality can have tragic results. In February 2013, nine-year-old Ella Kissi-Debrah died from respiratory failure.
The first inquest didn’t mention any environmental factors, but after a long fight by Ella’s mother, the coroner at a new inquest found: “Air pollution was a significant contributory factor to both the induction and exacerbations of her asthma. During the course of her illness between 2010 and 2013 she was exposed to levels of nitrogen dioxide (N02) and particulate matter in excess of World Health Organisation Guidelines.”
Ella lived in London, very near the South Circular Road, and the coroner pointed directly to traffic emissions as the “principal source of her exposure”.
Some pollution comes from natural sources (e.g. pollen or soil), but human activity is responsible for much of it.
While wood burning stoves have hit the headlines lately, emissions from tailpipes and tyre/brake wear make a significant contribution to poor air quality.
On top of that, these emissions are released in close proximity to people, inside and outside vehicles, and in urban areas are less likely to be swept away by wind because buildings line the roads.
The three main pollutants from motor traffic are:
- Nitrogen oxides: nitric oxide (NO) and nitrogen dioxide (NO2) – NO2 can inflame the airways and affect lung function
- Particulate matter: PM10 (coarse particles) and PM2.5 (fine particles) – PM is consistently associated with respiratory and cardiovascular illness and mortality. Tyre and brake wear also produce fine particles
- Carbon monoxide (CO): CO reduces the blood’s capacity to carry oxygen to body tissues, and is associated with strokes
Motor vehicles also emit: carbon dioxide (CO2), a greenhouse gas; sulphur dioxide (SO2); hydrocarbons (HC); and benzene (C6H6), which is carcinogenic.
From 2017-2021, road transport accounted for almost a third (31%) of the UK’s emissions of NO2, much more than the energy sector (19%) and manufacturing/construction (18%).
Road transport was also responsible for a sixth of PM2.5 (15%), and 13% of PM10.
In terms of NO2 emissions, road transport has exceeded all other sectors for 30+ years, but at least it has been trending downwards.
The share occupied by particulates, however, rose until about 2009 and, although it’s dropped since then, it is still a little above the level recorded in 1990:
Source of the table and chart above: DEFRA. Emissions of air pollutants.
Note: motor traffic dropped significantly during the restrictions caused by the pandemic, affecting emissions in 2020 and 2021.
Active travel and air quality
Walking and cycling are, as the House of Commons Environmental Audit Committee once described them, “the ultimate low emissions options”.
For short trips, or longer trips combined with public transport, higher levels of active travel could make a significant contribution to reducing pollution. About three-fifths of car trips are under five miles, after all. 
Dedicated, well-designed cycle infrastructure is essential, not just because it helps people make non-polluting trips, but also because facilities such as segregated cycle paths take space from cars and move motor traffic away from building façades where long-term exposure to exhaust fumes is likely to occur.
Some people, though – even members of the House of Lords – have claimed that cycle paths make air pollution worse because they reduce the space available for cars and slow them down. But analysis of cycle superhighways in London suggests that they are associated with reduced roadside concentrations of NO2 (by about -20% for every meter a road is moved away from a sensitive receptor).
Also, international evidence shows that cycle infrastructure causes overall reductions in traffic volumes and/or congestion levels (and thus presumably also pollution levels).
Cyclists and air pollution
Understandably, people worry about breathing in exhaust fumes and traffic-related dust when cycling along busy roads.
Although studies consistently find that cycling’s health benefits outweigh the risks, not all of them factor in traffic pollution. Of those that have factored this in, however, many conclude that cycling still does more good than harm and, generally speaking, that it is better to exercise (or cycle) in a polluted environment than to remain inactive.
For instance, a study of the benefits of shifting from driving to active travel concluded that “In any case the benefits of bicycling completely overwhelm any concern over pollution exposure of bicyclists.”
As other studies suggest, breathing rates influence how much pollution road users inhale, e.g. people travelling by cycle tend to breathe faster than those sitting in cars.
Breathing rates differ among cyclists too, of course – some ride quickly, others slowly, while some routes, or part of routes, involve more physical effort.
Also, whatever the breathing rate, how much pollution there is to breathe in from any particular surroundings depends on various factors. Route choice, proximity to tailpipes, how much stop/start occurs, weather, wind speed, presence of buildings or vegetation etc. may all make a difference to levels of exposure.
As for the influence of infrastructure, there’s good evidence to support the case for segregated cycle lanes as a way of minimising the inhalation of exhaust fumes, both to people cycling along them and to others.
Of course, people who cycle are not the only road users who breathe in fumes. Drivers do too because their cars suck in emissions through the engine compartment or via open windows.
So, the more people who cycle instead of driving – and the better the infrastructure that’s available for cycling becomes – the cleaner the air will be for everyone
- Excessively ‘smoky’ buses, coaches or lorries can be reported to the DVSA through www.gov.uk/report-smoky-vehicle
Please see attached briefing on research into cycling and exposure to vehicle exhaust and tyre/brake wear particles - link below.
Background: legislation and policy
Various laws, regulations and, within them, legally binding targets to reduce certain pollutants apply in the UK, some stemming from the EU. The UK is also covered by an Air Quality Strategy, which is reviewed and revised at intervals.
Responsibility for meeting air quality targets is a devolved matter, but it is the UK Government's job to ensure that national policies comply with any adopted international guidelines and agreements.
Where which law and which target applies is complicated both by devolution and by moves to revise and reform each of them, but summaries and pointers are available from:
- UK Air Information Resource
- Air quality in Wales
- Air Quality in Scotland
- Air quality Northern Ireland
Local authorities in the UK are required to manage air quality through the statutory Local Air Quality Management regime, which involves declaring an Air Quality Management Area (AQMA) for any place, street(s)/road(s)/area unlikely to achieve national air quality objectives, and producing an action plan to tackle it.
National and local government roles
Although action at local level is of course critical, Cycling UK’s believes all national governments should take an unambiguously leading role on improving air quality, and not leave the bulk of the action or paying for it to resource-strapped local councils.
We also believe that the UK/devolved nations should commit to delivering the World Health Organisation’s air quality guidelines, which are based on scientific evidence and recommend stringent limits for specific air pollutants.
Equally, we feel it’s imperative for active travel to be integral to all relevant policies and strategies at all levels of government, with decision-makers and practitioners in all departments – transport, health, environment, tourism, recreation, countryside etc. – working together to develop, implement, deliver and, importantly, monitor and evaluate them using robust data.
The following sections look at some of the measures we advocate.
Clean Air Zones (CAZs) and London’s Ultra Low Emission Zone (ULEZ)
Most AQMAs have not only been in place for many years, but also largely due to NO2 exceedance associated with roads. Clearly, there’s been little progress in all too many neighbourhoods – check yours out.
To improve air quality in their areas, local authorities can create Clean Air Zones (CAZs). It is up to them to decide whether or not to charge people for driving through them in a non-compliant vehicle, and which vehicles to include.
In Cycling UK’s view, all governments in the UK should adopt a presumption in favour of charging, rather than directing local authorities to give low-emission motor vehicles or buses greater priority.
This is because modelling suggests that charging schemes are more likely to reduce roadside NO2 concentrations than non-charging schemes, while London’s charging Ultra Low Emission Zone (ULEZ) reduced roadside concentrations of NO2 in the central zone by 44% in its first ten months.
We also think that private cars should not be exempt, and that the charges should be set at a level likely to maximise compliance.
As for the revenue generated, we believe it should be enough not only to cover administration costs, but also for some of it to fund high-quality infrastructure improvements to make non-polluting active travel more appealing.
Apart from anything else, this might put more local authorities in a better position to revoke their AQMAs, and reassure the people who are being charged that alternatives to driving are in place or, at least, on the way.
To ensure CAZs support pollution-free travel, we recommend covering them with plans to improve the local network for walking and cycling (e.g. Local Cycling & Walking Infrastructure Plans (LCWIPs, England) – air quality, in fact, is one of the factors local authorities are advised to consider in prioritising LCWIP improvements).
Road user charging/road pricing & taxes
Cycling UK believes in the ‘polluter pays’ principle, i.e. that those who cause pollution should pay for the harm it causes.
We therefore support the idea of a national framework(s) for road user charging (or ‘road pricing’) that would embody this principle. Not only would this help tackle emissions and encourage behaviour change, but also save individual local authorities a lot of work and make schemes more consistent.
Road pricing schemes can account for exhaust, time of day, location and/or distance driven by size of engine but, whatever form they take, they should be fair and equitable (e.g. for people living in rural areas).
The national tax system has an important role to play too, e.g. via fuel duty (which the Government consistently freezes) and emissions-based vehicle tax.
At the moment, the first Vehicle Excise Duty (VED) payment is based on CO2 emissions rather than pollutants affecting air quality and, thereafter, the rate for petrol or diesel cars is only affected by when and how payments are made. Electric vehicles go free.
In 2022, the Campaign for Better Transport found that 60% of people agreed that the current vehicle tax system should be reformed.
While electric/hybrid cars may help improve air quality in urban areas, shifting people away from driving to walking and cycling makes the best sense as it helps tackle physical inactivity and all the associated health problems.
Also, the impact of electric cars on the wider environment is compromised unless their power comes from a sustainable, pollutant-free source.
The sale of new petrol and diesel cars will end in the UK by 2030.
A nationally co-ordinated scheme rewarding people for scrapping their cars with a new cycle, e-bike, cargo cycle, season ticket etc instead, would help reducing total emissions from the UK’s vehicle fleet over time, not to mention the volume of motor traffic.
Asthma + Lung UK are calling for a scrappage scheme to be rolled out to areas that implement Class D CAZs (which include cars). Under the scheme, people on low incomes and/or whose mobility is affected by lung and other health conditions would be invited to exchange any polluting vehicles for a financial grant to spend on an active travel option; public transport use; or an electric vehicle.
According to a report on scrappage schemes in London,10% of grant recipients said they walked and/or cycled more as a result (for walking, the net increase was 22%; for cycling, 5%).
One way for local authorities to promote non-polluting transport is to organise ‘car-free’ days by temporarily closing off roads to motor vehicles through traffic regulation orders.
This can be done regularly, as part of annual nationwide events (e.g. on Car Free Day, traditionally on 22 September every year).
Planning – i.e. if, how and where to build or expand developments – can enable non-polluting and active travel and reduce car-dependency, or it can do the exact opposite. For more see Cycling UK’s briefing on planning and land use.
See also Environmental Protection UK and the Institute of Air Quality Management guidance on air quality for professionals working in the planning system.
The link between air quality and travel choice needs to be made far more obvious to the public through targeted awareness campaigns.
For maximum effect, campaigns should not simply alert people to high levels of pollution and how to keep themselves safe, but also to how changes in their behaviour could improve outdoor air quality in the first place.
Further reading and websites (see also links in text above)
- Air Quality News – offers regular updates
- Chief Medical Officer's Annual Report 2022: Air pollution
- Clean Air in London – campaign to achieve full compliance with WHO guidelines for air quality throughout London and elsewhere
- ClientEarth - have pursued the UK government in court over illegal levels of pollution
- Committee on the Medical Effects of Air Pollutants
- European Environment Agency: Explaining road transport emissions: A non-technical guide (2016).
- Health Air Cymru – campaigning for clean air in Wales (Cycling UK Cymru is a member)
- Healthy Air Coalition – UK campaign for clean and healthy air (Cycling UK is a partner)
- Local Government Association – Air quality: a briefing for directors of public health
- National Atmospheric Emissions Inventory Interactive Map
- National Highways (England) on air quality
- NICE guidance on outdoor air quality and health
- Public Health England – Improving outdoor air quality and health: review of interventions
- Transport for London on air quality
- World Health Organisation’s work on air quality and air quality database