Originally posted to the Fraser of Allander Institute’s Blog

Introduction

In Glasgow, poorer communities have significantly worse health outcomes than wealthier ones – men born in wealthy areas can expect to outlive men born in deprived areas by upwards of 15 years. While poorer people have shorter life expectancies in most cities and countries, the gap in life expectancies between wealthy and poor areas is especially profound in Glasgow, where it can exceed 15 years.

Glasgow also has some of the worst air quality levels in Scotland. This is unsurprising, since Glasgow is Scotland’s most populated city, but air quality can cause significant health problems – this is especially important, given the extent to which health inequality affects the city.

While health and air quality are strongly correlated, and health and income are closely related, the relationship between air quality and income is more complex. Commonly, we think of air quality and income being directly related in cities, with worse air quality affecting neighbourhoods with lower income. While there is some evidence that this is the case in Glasgow, this is generally not the case for other cities across the UK – in most urban areas, both high and low-income neighbourhoods experience poorer air quality compared to middle-income neighbourhoods, which are generally more removed from both popular city centre areas and industrial areas. This relationship varies from city-to-city, so examining environmental inequalities related to air pollution should be considered on a case-by-case basis.

There’s a lot to examine in this area to understand how different neighbourhoods experience pollution. Understanding how poor air quality interacts with regional and social inequalities is also relevant, especially for policymakers seeking to improve air quality, as well as understanding the economic drivers of poor health.

In this project, we will be examining the relationship between health, income, and environmental inequality in neighbourhoods across Glasgow, focusing on groups across the city which may be more susceptible to or affected by poor air quality, such as children, disabled people, or people from a minority ethnic background.

This is an interesting area to examine further. Glasgow has made strides in improving air quality, with mean air pollutant concentrations consistently declining at monitoring sites across the city over the past 15 years (The Glasgow Indicators Project, 2023). but given its vast gaps in health outcomes and household incomes, needs to continue to understand how pollutants affect different populations.

This article provides an introduction into air pollution, health inequality, and income inequality, both in general and in Glasgow specifically, setting the stage for future research in this space under the GEMINOA project.

Air pollution and health

Before diving into the relationship between health and air quality, it’s important to define “poor air quality.” The main pollutants responsible for health problems are listed in Table 1. These generally come from burning fuels and vehicle wear when they’re outside, and from cooking, heating, or chemical products inside. Biologic agents, especially mould, also contribute to pollutant concentrations, and can cause significant health problems. Particulate matter and nitrous oxides are the most important to note – they are routinely tracked by local authorities, and there is a substantial amount of evidence on the way they affect health.

Table 1: Common health impacting air pollutants and their main source (Source: DEFRA, NICE)

Pollutant	Abbreviation	Main source of pollutant (outdoors)	Main source of pollutant (indoors)
Nitrogen oxides	\(NO_x\)	Vehicle emissions	Burning fuels, especially for cooking or heating; tobacco; outdoor sources
Nitrogen dioxide	\(NO_2\)	(as above)	(as above)
Coarse particulate matter (measuring less than 10 micrometres in diameter)	PM10	Particulate matter refers to any non-gaseous matter with a diameter below 10µm or 2.5µm. Most PM concentrations come from inorganic matter from human activity, such as black smoke, vehicle emissions, and vehicle wear. Concentrations also include biologic agents (such as pollen) and inorganic matter unrelated to human activity (such as ocean spray)	Burning fuels, household chemical products, tobacco, biologic agents (such as mould, bacteria, viruses, pet dander, or pollen), outdoor sources, indoor activities such as dusting and vacuuming.
Fine particulate matter (measuring less than 2.5 micrometres in diameter)	PM2.5	(as above)	(as above)
Ozone	\(O_3\)	Reactions between other pollutants and ultraviolet radiation	-
Volatile organic compounds	VOCs	-	Cleaning products, paint or other home décor products, aerosol sprays, personal cleaning
Polycyclic aromatic hydrocarbons	PAHs	-	Burning fuels, especially for cooking or heating; tobacco

Although pollution is very much a health concern, the UK has relatively good air quality on a global scale, with Scotland generally having lower levels of harmful air pollutant concentrations compared to other UK countries (Davies, 2022; IQAir, 2023). As a result, people living in Scotland may not experience health problems to the severity of other countries, or it may be difficult to prove a link between some diseases and pollutant levels in countries with relatively clean air. While levels in Glasgow are high relative to Scotland, they are low on a global scale.

This is not to say that people in Scotland are free from health issues related to air pollution. Poor outdoor air quality has been shown to be related to respiratory problems in Scotland, although there are numerous health outcomes that are correlated with air quality in countries with similar levels of pollution. PM2.5 has an especially large body of literature showing associations between exposure and a variety of poor health outcomes, such as asthma and COPD (see Table 2). These outcomes are also more likely to affect sensitive populations, such as the elderly, children, and pregnant women (Walker et al., 2023).

Indoor air pollution has much of the same overall health impacts as outdoor air pollution, although enclosed spaces tend to have a more diverse range and higher concentration of pollutants. In addition, indoor sources, particularly those related to human behaviour (i.e., cooking or smoking) can cause significant pollution peaks. Ventilation is a critical factor as it can dictate the rate of dissipation of air pollution. People also spend the majority of their time indoors, especially in the UK, so indoor pollutants can be a serious health risk (Table 3). These health outcomes are also more significant for vulnerable populations (National Institute for Health and Care Excellence, 2020).

Outdoor pollution can also affect indoor pollution. Buildings with more ventilation or draughts have lower concentrations of indoor air pollution but higher levels of outdoor air pollution. Making buildings more airtight, in contrast, increases indoor pollutant concentrations while reducing the amount of outdoor pollution exposure. This is something of a double-edged sword: making homes more airtight makes them more energy efficient and reduces exposure to outdoor pollutants, but may actually make indoor air quality worse (Scottish Government, 2023a).

Table 2: Outdoor air pollutants and observed health outcomes in countries with pollution levels similar to Scotland (Source: Scottish Government)

Outdoor Pollutant	Health outcome
PM2.5	Behavioural problems, breast cancer mortality, cardiovascular disease and mortality, cognition problems, dementia, mental health conditions, motor delay, neonatal disorders, respiratory mortality, type 2 diabetes
PM10	Breast cancer mortality
\(NO_X\)	Cognition problems, mental health conditions
\(NO_2\)	Asthma incidence, worsened COPD outcomes
\(O_3\)	Asthma incidence, Parkinson’s disease

Table 3: Indoor air pollutants and associated health outcomes in regions similar to Scotland (Source: Exley et al., 2022)

Indoor Pollutant	Health outcome
PM10, PM2.5	Cardiovascular disease and mortality, respiratory illness and mortality, declining cognitive function and dementia, adverse pregnancy-related outcomes, diabetes
\(NO_x\) & \(NO_2\)	Increased prevalence and worsened outcomes for respiratory illnesses
VOCs	Short-term airway irritation and headaches; respiratory effects; possibly cancers. Note that VOCs are generally not thought to be a major health issue when homes are well-ventilated, and products are used responsibly.
PAHs	Lung cancer
Biologic agents	Allergies, worsened outcomes for asthma or COPD

Air pollution and household income

In many countries, poorer people living in urban areas experience worse air quality than those on higher incomes. This relationship isn’t as straightforward in urban areas in the UK, where low- and high-income neighbourhoods alike tend to experience higher levels of pollution than middle income areas. This is generally because middle income households have access to cars, which allows them to move away from more polluted areas. Wealthier households, however, are able to afford higher-priced housing in trendier, more densely populated areas (Bailey et al., 2018). Even within the UK, there is a wide range of environmental inequalities in urban areas, so research into local inequalities need to be considered on a case-by-case basis.

Previous research into Scottish cities found different trends in each area, although Glasgow had a more direct relationship between higher levels of exposure to outdoor PM2.5 and higher levels of income deprivation in Glasgow (Bailey et al., 2018; Ferguson et al., 2021). Income deprivation, which is a measure from the Scottish Index of Multiple Deprivation (SIMD), is a proxy for understanding relative household income levels. Rather than showing how much households make on average in an area, however, it ranks neighbourhoods based on household income, with the bottom 20% of neighbourhoods classified as “income deprived.”

While this is a commonly used metric for understanding income inequality, it comes with some issues. Two areas may have similar income levels but very different SIMD rankings – there are nearly 7,000 such neighbourhoods (called “data zones”) in Scotland. The SIMD treats the difference between the lowest ranking data zone and the 700th lowest the same as the difference between the highest and the 700th highest-ranking neighbourhood, for instance. In practice, the bottom 10% of data zones may be much closer in median household income levels compared to the top 10%. SIMD rankings, in general, fail to capture low income neighbourhoods in urban areas (McCartney and Hoggett, 2023).

Household income and income deprivation are both highly correlated to levels of indoor air pollution. Households in lower income areas tend to have higher levels of exposure to PMs, VOCs, and NOx.

There are a few reasons for this. Lower quality housing is often located in areas with more outdoor air pollution, and poor-quality housing is often draughty, allowing for further interaction with outdoor air pollution. Overcrowding, which is more common among low-income households, can also increase the concentration of pollutants. People with lower incomes may also not be able to access or afford improvements to their housing. Interventions to reduce damp and mould, for instance, may be too expensive, or may not be easy to arrange through landlords in rental housing. Furthermore, some choices, such as smoking, are more common in low income households, and add to pollution concentrations (Exley et al., 2022).

Inequality in Glasgow

Given that there is a relationship between air quality and household income, it’s important to understand what household income looks like for Glasgow. Looking beyond air quality, health as a whole is highly correlated to household income, with people in poorer households having notable worse health outcomes compared to wealthier people.

Glasgow has an especially wide range of health and income inequalities. Notably, Glasgow has a higher concentration of income-deprived neighbourhoods than anywhere else in Scotland, low-income neighbourhoods are disproportionately located in Glasgow. One fourth of the most deprived areas¹ in Scotland are located within Glasgow city council (Scottish Government, 2020).

Household income inequalities are also worse for different demographics, such as children, ethnic minorities, and people with disabilities. As of 2022, Glasgow City has the highest proportion and overall highest number of children living in poverty out of all Scottish local authorities (DWP, 2023). Ethnic minorities are more than twice as likely to be in poverty than people from a white background (Scottish Government, 2023b). Although it’s not clear how many people from an ethnic minority are in poverty in Glasgow, it is worth noting that Glasgow has the highest proportion and largest population of non-white ethnic minorities living in Scotland (Walsh, 2017). Finally, relative poverty rates among disabled people are also higher than the non-disabled population, and similarly, Glasgow has the highest rates of disability among working-aged adults out of all Scottish cities (Understanding Glasgow, 2016).

Glasgow is also a uniquely extreme case of health inequality: the city has an exceptionally large gap in life expectancies in the most and least deprived neighbourhoods. Men born in Govan, for instance, can expect to live 15 years less than men born just a few miles away in Pollokshields. These gaps have been consistent for the better part of a century and are more extreme than cities with similar levels of deprivation, such as Manchester or Liverpool (Whyte, Young and Timpson, 2021).

Glasgow has the lowest life expectancy of any Scottish local authority. Scotland itself has a remarkably low average life expectancy – in fact, it is the lowest in Western Europe, in spite of being one of the wealthiest countries (Scottish Government, 2022).

How does air pollution relate to health and income inequality in Glasgow?

There is a lot of UK-wide research into the relationship between health, household incomes, and air pollution, but very little specific to Scotland, and even less for Glasgow in particular.

That’s not to say that no data exists at all. Outdoor pollution levels are tracked and modelled across the city. Pollutant concentration tends to be highest around the city centre, central motorways, and adjoining neighbourhoods (Wareham et al., 2023). It is not clear how indoor air pollution varies across the city, although low-income households are likely to experience higher levels of pollution (Exley et al., 2022).

The relationship between air quality and household incomes, again, varies widely by city, and there is little research between these two indicators in Glasgow. Research from 2018 found a linear relationship between income deprivation and PM2.5 exposure, where income deprived areas had higher levels of pollutant exposure, but this result hasn’t been re-examined recently (Bailey et al., 2018).

There is apparently no previous research examining pollutant exposure among different demographics in Glasgow, so it is unclear the extent to which air pollution affects populations such as ethnic minorities, pensioners, children, or disabled people. In the UK, all of these populations either encounter higher levels of pollution or are more affected by it, but there is no localised data illustrating the extent of the problem (Gadd et al., 2023).

The relationship between various health outcomes and air pollution in Glasgow is also limited. There is a clear relationship between pollution in Glasgow and respiratory ailments, but not for other diseases. One long-term study also found a relationship between cardiovascular disease and emissions in Paisley, although short-term studies were not able to establish a similar correlation (Walker et al., 2023).

These knowledge gaps are significant for Glasgow. While there have been several policies aimed at reducing the overall level of pollution in the city, there may be localised actions that can also be taken to help underserved communities.

What’s next?

The next step for this research is to examine the available data and to describe the relationship between health, household income, demography, and air quality for Glasgow neighbourhoods. This can provide important context to the existing drivers of health inequalities within the city, and a background to understanding the impact that air quality interventions might have on areas with different socioeconomic backgrounds.

So far, data on median household incomes and age distribution is available at a data zone level. There are around 750 data zones in Glasgow. Various health outcomes are available at an intermediate zone level, which covers around 10 data zones; there are 136 intermediate zones in Glasgow. PM and NOX concentrations are modelled across the UK down to a very small scale – pollutant concentrations can be found down to a 1km2 area. There is some challenge in mapping these small areas to data zone and intermediate zone level, but the data exists. Finding proportionate data on ethnic minorities at a data zone level is trickier – there is data from the 2011 census which is publicly available, although this is fairly out-of-date. New census data is not likely to be available for another year, so we are exploring other avenues of understanding the ethnic backgrounds of neighbourhoods across Glasgow.

We also have novel data on air pollutant concentrations at schools across the city through this project. We can map out the relationship between school-level air quality data and the ethnic, household deprivation, and disability background of the student population through the annual school census.

Alongside this workstream, we will be looking into the relationship between economic activity and emissions across Scottish local authorities, in order to understand how the UK measures local reductions in emissions. In particular, we want to understand whether or not local policy actions actually reduce emissions, and whether those local emission reductions are accurately reflected in UK-wide measurements.

Keep an eye on the GEMINOA project page for future insight into air quality and emissions in Glasgow City.

About GEMINOA

The Glasgow Environmental Monitoring of Indoor and Outdoor Air (GEMINOA) project is a collaboration between the Architecture, Electronic and Electrical Engineering, and Economics departments at the University of Strathclyde. In partnership with Glasgow City Council, Glasgow Science Centre, SmartSTEMs, and the University of California Berkeley, this project combines data from novel outdoor air quality and emissions sensors, indoor air quality data and economic analysis to support public engagement and aid policy makers in evaluating and measuring impacts of policies.

This project is funded through Local Governments for Sustainability (ICLEI).

References

• Bailey, N. et al. (2018) ‘Reconsidering the Relationship between Air Pollution and Deprivation’, International Journal of Environmental Research and Public Health, 15(4), p. 629. Available at: https://doi.org/10.3390/ijerph15040629.
• Davies, R. (2022) Why is air quality bad today - and how does Scotland’s air quality compare to the rest of the UK?, The Scotsman. Available at: https://www.scotsman.com/news/environment/air-pollution-why-is-air-quality-bad-today-and-how-does-scotlands-air-quality-compare-to-the-rest-of-the-uk-3625066 (Accessed: 23 February 2024).
• DWP (2023) Children in low income families: local area statistics, financial year ending 2022, GOV.UK. Available at: https://www.gov.uk/government/statistics/children-in-low-income-families-local-area-statistics-2014-to-2022/children-in-low-income-families-local-area-statistics-financial-year-ending-2022 (Accessed: 15 February 2024).
• Exley, K. et al. (2022) ‘1. Air pollution and health’, in C. Whitty and D. Jenkins (eds) Chief Medical Officer’s Annual Report 2022.
• Ferguson, L. et al. (2021) ‘Systemic inequalities in indoor air pollution exposure in London, UK’, 2(1), pp. 425–448. Available at: https://doi.org/10.5334/bc.100.
• Gadd, L. et al. (2023) How will the climate and nature crises impact people from Black, Asian and Ethnic Minority Communities? Race Equality Foundation.
• IQAir (2023) World’s Most Polluted Countries in 2022 - PM2.5 Ranking. Available at: https://www.iqair.com/gb/world-most-polluted-countries (Accessed: 23 February 2024).
• McCartney, G. and Hoggett, R. (2023) ‘How well does the Scottish Index of Multiple Deprivation identify income and employment deprived individuals across the urban-rural spectrum and between local authorities?’, Public Health, 217, pp. 26–32. Available at: https://doi.org/10.1016/j.puhe.2023.01.009.
• National Institute for Health and Care Excellence (2020) Indoor air quality at home. NICE guideline NG149.
• Scottish Government (2020) Scottish Index of Multiple Deprivation 2020v2 local and national share calculator. Available at: http://www.gov.scot/publications/scottish-index-of-multiple-deprivation-2020v2-local-and-national-share-calculator-2/ (Accessed: 15 February 2024).
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• Understanding Glasgow (2016) Working age disability. Available at: https://www.understandingglasgow.com/indicators/health/comparisons/with_other_pla**ces/disability_scottish_cities/scottish_cities (Accessed: 15 February 2024).
• Walker, B. et al. (2023) Review and Assessment of the Evidence on Health Impacts of Low-Level Pollution in Countries with Levels of Ambient Air Pollution Comparable to Scotland. RESAS/020/20. Scottish Government.
• Walsh, D. (2017) ‘The changing ethnic profiles of Glasgow and Scotland, and the implications for population health’.
• Wareham, J. et al. (2023) Scottish Air Quality Maps.
• Whyte, B., Young, M. and Timpson, K. (2021) Health in a changing city: Glasgow 2021. Glasgow Centre for Population Health.