In our Expert Briefing Series, the Centre for Climate Engagement at Hughes Hall talks to academics and industry experts about key climate-related topics.
This briefing explores the relationship between air pollution, health risks and climate change with Dr Neil Saad and Nick Scott. It has been developed in collaboration with Dr Neil Saad, Visiting Fellow at Hughes Hall, University of Cambridge and Nick Scott, Content Lead at the Centre for Climate Engagement
- Air pollution has significant short- and long-term impacts for human health, including respiratory disease, stroke and heart attack, resulting in around 28,000 premature deaths in the UK each year.
- Air pollution and climate change are closely related; addressing the two issues in parallel would reduce the cost of decarbonisation and largely deliver health improvements.
- Current UK regulation on air quality lags behind the latest WHO guidance. Greater monitoring and public awareness of air pollutants and their sources is needed to stimulate action on air pollution and climate change.
Air pollution is estimated to be responsible for around 28,000 premature deaths in the UK each year[i]. Extreme heat associated with climate change can increase pollution levels and exacerbates the health effects of breathing polluted air. There are significant benefits from tackling poor air quality and climate change in parallel, especially as they have common sources such as the burning of fossil fuels and the management of nitrogen in agriculture. Meanwhile, some decarbonisation measures considered in isolation, such as the switch to biofuels requiring fertilisers, can negatively impact the air that we breathe. While the UK Government acknowledges the interrelationship, the two issues are still largely addressed separately. This briefing explores the links between climate change, air pollution and health and the need for a holistic approach to policy development.
The nexus between air pollution and climate change
Air pollution is the contamination of the air we breathe by small particles and gases. Polluting gases include carbon monoxide, ozone, nitrogen dioxide and sulphur dioxide. Particles or particulate matter (PM) are small pieces of dust, dirt or soot classified by size rather than chemical composition, e.g. PM10 which are particles with a diameter less than or equal to 10 microns[ii].
These contaminants are close cousins of the major greenhouse gases causing climate change and come from similar sources. Like carbon dioxide (CO2) and methane, most air pollutants come from burning fossil fuels, whether from driving cars, generating electricity, or operating industrial plants. In emerging economies, cooking and heating, particularly using coal and wood, also contribute to air pollution[iii]. Another significant contributor to both air pollution and greenhouse gases is the management of nitrogen in agricultural systems.
Climate change and air pollution are related in other ways. The impacts of climate change exacerbate air pollution. For example, extreme heat increases the number of wildfires which, in turn, release more polluting gases and particulate matter into the atmosphere. Stagnant weather conditions, such as the heat domes affecting large parts of Europe and the southern USA in summer 2023, prevent pollutants from dispersing, resulting in accumulation and prolonged exposure to harmful pollutants.
Similarly, higher concentrations of greenhouse gases in the atmosphere, particularly methane, speed up the formation of ozone, a highly irritant gas, resulting in higher levels of ozone pollution. This effect is known as the ‘climate penalty’[iv].
Health risks of air pollution and climate change:
a cumulative effect
Exposure to polluted air has serious consequences for public health. These impacts vary in severity and can be short or long term. Air pollution is estimated to be responsible for around 28,000 premature deaths in the UK each year[v].
Short-term impacts include respiratory problems due to breathing poor quality air, such as greater incidence of severe asthma attacks and increased hospital or healthcare visits[vi], while longer-term impacts include bronchial and lung cancers. In addition, air pollution is associated with increased incidence of several non-communicable diseases, including obesity, type II diabetes and stroke[vii]. Other studies have also found links between air pollution and low birth weights or the frequency of pre-term births[viii].
Meanwhile, there is increasing evidence that instances of severe impacts decline when measures to reduce the levels of air pollution are introduced. For example, the introduction of low emission zones restricting the type and age of vehicles that can be used in cities across the world has been associated with up to a 5% drop in heart problems and as much as a 10% drop in strokes[ix].
Climate change not only increases pollution levels, it also adversely impacts health in other ways. Extreme heat makes it harder to breathe and causes heat stress, making strokes and heart attacks more likely[x]. Moreover, extreme climatic events are increasing in frequency due to climate change. As noted, climate change also results in more pollutants being released, e.g. via wildfires, while stopping pollutants from dispersing, resulting in higher risk of health problems from pollution.
The concurrent exposure of, for example, heat stress due to climate change and air pollution both exert health effects on the individual, with one health effect aggravated by the impact of the other. ‘It’s a cumulative effect,’ Saad notes.
The unequal distribution of health risks
‘The impact of climate change and/ or air pollution is not equally distributed,’ Saad comments. ‘The health impact is the greatest on those that are already most disadvantaged.’ The old and the very young are particularly at risk, as well as pregnant people and the immunocompromised[xi].
Children breathe in more air relative to their bodyweight than an adult making them more vulnerable to the damaging effects of air pollution. Moreover, their biological defence mechanisms are less developed, making it harder for their bodies to recover from the impacts of high pollution, whether that is detoxifying and ridding the chemicals from their system or repairing damage from pollutants. They also have a smaller airway, which can be more easily constricted[xii].
Economic disparities have an important part to play in health impacts, according to Saad. ‘Those living in poor housing conditions might be more exposed to particulate matter if they’re indoors in winter, due to exposure to poor quality heating systems. They might be living in an area that’s very urban and highly congested. So there might be more air pollutants in the direct environment when they go outdoors.’
People in disadvantaged areas have less access to green space and the beneficial impacts of nature in absorbing air pollutants. Contamination levels may be lower in an affluent area in a city, such as Hampstead Heath, than close to an out-of-town industrial site or in an area of dense social housing close to a rural community due to the absence of mitigating factors[xiii].
An opportunity to raise joint ambition on air quality and climate policy
Air pollution and climate change share common sources, including the management of nitrogen in the agricultural system and the burning of fossil fuels. There is ‘unequivocally’ a benefit in tackling both issues in parallel, Saad comments. ‘You’re basically killing two birds with one stone.’ It is critical that society starts to view the two issues in these terms, to increase traction around new policies.
While the UK Government acknowledges the interrelationship with climate change, transitioning to a low-carbon future and reducing air pollution are largely treated as separate issues. The Clean Air Strategy points to instances where climate policy may offer benefits for air quality[xiv]. For example, the Renewable Heat Incentive designed to encourage the electrification of heating also sets out strict limits on particulate matter emissions.
The Clean Air Strategy also highlights areas where action to tackle climate change may negatively affect air quality, e.g. burning biomass instead of fossil fuels for power generation.
The UK’s regulation on air quality lags behind recommendations from the World Health Organization (WHO), despite the Committee on the Medical Effects of Air Pollutants regarding the guidelines as ‘long-term targets to inform policy development’[xv]. Current regulation on air quality is line with the WHO 2005 Global Air Quality Guidelines. However, it has not been adjusted since WHO updated its guidance in 2021.
Current regulation on air quality in the UK stems from EU law. In England, standards are governed by the Air Quality Standards Regulations 2010. There are equivalent Air Quality Standards Regulations in each of the devolved nations.
The regulations set ‘limit values’ for each pollutant. The average concentration of a pollutant cannot exceed the limit more than a defined number of times in a set period[xvi]. In most instances, limit values are the same for all parts of the UK, though at 10μg (micrograms) Scotland has stricter limits for PM2.5. The equivalent limit in other parts of the country is 20μg. This compares with a limit of 5μg on PM2.5 under the latest WHO guidance. Scotland and Northern Ireland have also set lower limit values for benzene, an indoor air pollutant.
Doubling down on action to improve health
Localised action to improve air quality by reducing emissions at source not only contributes to improved health of the local residents, but also to broader human and planetary health.
Measures to tackle air pollution are usually localised and focused on tackling regional health impacts, such as the introduction of low emission zones to reduce pollution in defined urban areas. Measures to counter air pollution in Delhi, Beijing or Cairo have little immediate impact on air quality in the UK. As Saad points out, ‘The immediate health effects are local. Pollution in Cairo doesn’t directly affect the health of a person in London, but the emissions released in Cairo do contribute to global warming and climate change globally. You cannot forget the global perspective because gases once released, they go into the air.’
Climate change can also undermine the impact of highly localised air pollution measures. The impact of wildfires in Canada has been felt in big cities across the United States. For example, wind has transported high levels of particulate matter into New York where it has become trapped between the tall buildings and been unable to disperse, resulting in higher contaminant levels despite any local efforts to reduce air pollution[xvii].
Saad also believes there needs to be greater emphasis on the short-term benefits of tackling air pollution. Air pollution is adding to the immense stress that the NHS is already under. There is a direct correlation between air pollution measures and hospital admissions. The introduction of the Ultra-Low Emission Zone (ULEZ) to central London has contributed to a 30% reduction in children being admitted to hospital with asthma in inner London[xviii]. Focusing on some of these key interrelations which are easy to comprehend will help to increase urgency of action[xix].
Unless levels are very high, air pollution is generally invisible. This makes it hard for individuals to determine how good, or bad, the air quality is in their local area and how pollution levels are changing from day to day. ‘For a lot of people, it doesn’t hit home,’ Saad says, adding that, ‘if it doesn’t hit home, it’s harder to care about it, especially when faced with a cost of living crisis and people are concerned with more tangible issues, such as increased rent and higher mortgage payments or food prices.’
‘One of the things that would help is more measuring, monitoring and information sharing,’ Saad suggests. ‘If you have more information on air pollution levels, particularly in their local area, available to the general public, then they will become aware and can push for action.’ This will result in greater pressure on politicians to tackle air quality, just as there is growing public demand for action on climate change or water quality.
Greater public awareness could also help to reduce resistance to air quality measures. Some Londoners feel the expansion of the ULEZ will either restrict their ability to use their car or require them to buy a new vehicle. They do not see the benefits. ‘They will probably be breathing less polluted air, but they don’t see it,’ Saad explains. More monitoring and information sharing could help to increase awareness and increase understanding of the health impacts of polluted air.
Responsibility for air quality standards rests with the individual governments and devolved assemblies for the constituent nations of the UK, while many measures – such as emissions zones – are implemented at a local level. Despite the acknowledged links between air pollution and climate change and the fact that efforts to decarbonise heating, energy generation, transportation and agriculture have benefits for air quality and, in turn, for public health, the two issues continue to be addressed separately much of the time. Tackling the two issues in concert would increase traction around new policies and generate cost efficiencies. Greater measuring and information sharing of air quality levels would also help to improve public awareness of air pollution and the impact of extreme weather events on air quality, leading to greater demand for action.
- [i] The Royal Society, November 2021, Effects of net-zero policies and climate change on air quality
- [ii] World Health Organization, 19 December 2022, Ambient (outdoor) air pollution, and World Health Organization, 28 November 2022, Household air pollution
- [iii] Mohajeri, N., Hsu, S.-C., Milner, J., Taylor, J., Kiesewetter, G., Gudmundsson, A., Kennard, H., Hamilton, I. and Davies, M, August 2023, ‘Urban–rural disparity in global estimation of PM2·5 household air pollution and its attributable health burden’, The Lancet, and Gordon, S. B., Bruce, N. G., Grigg, J., Hibberd, P. L. Kurmi, O. P., Lam, K. H., Mortimer, K., Asante, K. P., Balakrishnan, K., Balmes, J., Bar-Zeev, N., Bates, M. N., Breysse, P. N., Buist, S., Chen, Z., Havens, D., Jack, D., Jindal, S., Kan, H., Mehta, S. and Martin, W. J., October 2014, ‘Respiratory risks from household air pollution in low and middle income countries’, The Lancet Respiratory Medicine, Vol. 2, Issue 10, pp. 823-860
- [iv] US Environmental Protection Agency, 15 February 2022, ‘How Climate Change May Impact Ozone Pollution and Public Health through the 21st Century’
- [v] The Royal Society, November 2021, ‘Effects of net-zero policies and climate change on air quality’,
- [vi] Atkinson, R. W., Kang, S., Anderson, H. R., Mills, I. c. and Walton, H. A, 2014, ‘Epidemiological time series studies of PM2.5 and daily mortality and hospital admissions: A systematic review and meta-analysis’, Thorax, Vol. 69, Issue 7
- [vii] European Environment Agency, 23 May 2023, How air pollution affects our health,; Shah, A. S. V., Lee, K. K., McAllister, D. A., Hunger, A., Nair, H., Whiteley, W., Langrish, J. P, Newby, D. E. and Mills, N. L, 24 March 2015, ‘Short term exposure to air pollution and stroke: systematic review and meta-analysis’, The BMJ, and Schraufnagel, D. E., Balmes, J. R., Cowl, C. T., De Matteis, S., Jung, S.-H., Mortimer, K. Perez-Padilla, R., Rice, M. B, Riojas-Rodriguez, H., Sood, A., Thurston, G. D., To, T., Vanker, A. and Wuebbles, D. J., February 2019, ‘Air Pollution and Noncommunicable Diseases: A Review by the Forum of International Respiratory Societies’ Environmental Committee, Part 2: Air Pollution and Organ Systems’, Chest, Vol. 155, Issue 2, pp. 417–426
- [viii] Ghosh, R., Causey, K., Burkart, K., Wozniak, S., Cohen, A. and Brauer, M, 28 September 2021, ‘Ambient and household PM2.5 pollution and adverse perinatal outcomes: A meta-regression and analysis of attributable global burden for 204 countries and territories’, PLOS Medicine, and European Environment Agency, 24 April 2023, Air pollution and children’s health
- [ix] Chamberlain, R. C., Fecht, D., Davies, B., Laverty, A. A., July 2023, ‘Health effects of low emission and congestion charging zones: a systematic review’, The Lancet, Vol. 8 Issue 7; see also Fuller, G., 30 June 2023, ‘Low emission zones are improving health, studies show’, The Guardian
- [x] Liu, J., Varghese, B. M., Hansen, A., Zhang, Y., Driscoll, T., Morgan, G., Dear, K., Gourley, M., Capon, A. and Bi, P., June 2022, ‘Heat exposure and cardiovascular health outcomes: a systematic review and meta-analysis’, The Lancet Planetary Health, Vol. 6, Issue 6
- [xi] Paciência, I., Rufo, J. C. and Moreira, A., 17 June 2022, ‘Environmental inequality: Air pollution and asthma in children’, Pediatric Allergy and Immunology, Vol. 33, Issue 6, ; Garcia, E., Rice, M. B. and Gold, D. R., July 2021, ‘Air pollution and lung function in children’, Journal of Allergy and Clinical Immunology, Vol. 148, Issue 1, pp. 1-14; Tibuakuu, M., Michos, E. D., Navas-Acien, A. and Jones, M. R., December 2018, ‘Air Pollution and Cardiovascular Disease: A Focus on Vulnerable Populations Worldwide’, Current Epidemiology Reports, Vol. 5, pp. 370-378, and Chang, A. Y., Tan, A. X., Nadeau, K. C. and Odden, M. C, 19 April 2022, ‘Aging Hearts in a Hotter, More Turbulent World: The Impacts of Climate Change on the Cardiovascular Health of Older Adults’, Global Cardiovascular Health, Vol. 24, pp. 749-760
- [xii] Perera, F. and Nadeau, K., 16 June 2022, ‘Climate Change, Fossil-Fuel Pollution, and Children’s Health’, New England Journal of Medicine, Vol. 386, pp. 2,303-2,314
- [xiii] Nieuwenhuijsen, M. J., Khreis, H., Triguero-Mas, M., Gascon, M. and Dadvand, P., January 2017, ‘Fifty Shades of Green:Pathway to Healthy Urban Living’, Epidemiology, Vol. 28, Issue 1, pp. 63-71, and Barboza, E. P., Cirach, M., Khomenko, S., Iungman, T., Mueller, N., Barrera-Gómez, J., Rojas-Rueda, D., Kondo, M. and Nieuwenhuijsen, M., October 2021, ‘Green space and mortality in European cities: a health impact assessment study’, The Lancet Planetary Health, Vol. 5, Issue 10
- [xiv] UK Government, January 2019, Clean Air Strategy 2019
- [xv] UK Health Security Agency, 27 July 2022, COMEAP statement: response to publication of the World Health Organization Air quality guidelines 2021
- [xvi] For a full list of limit values see: DEFRA, 2010, National air quality objectives and European Directive limit and target values for the protection of human health
- [xvii] Dong, M., Malsky, B., Gamio, L., Bloch, M., Reinhard, S., Abraham, L, González, M., Judson Jones, G., Murphy, J.-M. and Hernandez, M., 21 August 2023, ‘Maps: Tracking air quality and smoke from wildfires’, The New York Times
- [xviii] Smith, R., 6 April 2023, 6th April 2023, Doctors need to speak up about clean air in London and other cities’, UK Health Alliance on Climate Change
- [xix] Schraufnagel, D. E., Balmes, J. R., De Matteis, S., Hoffman, B., Kim, W. J., Perez-Padilla, R., Rice, M., Sood, A., Vanker, A. and Wuebbles, D. J., 2019, ‘Health Benefits of Air Pollution Reduction’, Annals of the American Thoracic Society, Vol. 16, Issue 12