Linking the Chemical Composition of Air Pollution to Differential Exposure and Inequalities in the UK

Summary

This project explores how the composition of outdoor and indoor PM₂.₅ , along with other air pollutants, relates to differential exposure and socio-economic and health inequalities in the UK. Eligibility: UK students only.

See: https://geosciences.ed.ac.uk/study/degrees/research-degrees/phd-projects/physical-sciences?item=1857

Project background

Air pollutant concentrations are determined by emissions, atmospheric chemistry, and deposition processes that act as sinks. These processes together determine the lifetime of an air pollutant in the atmosphere. Nitrogen dioxide (NO2) and Particulate Matter (PM2.5, PM10; particulate matter with a diameter of 2.5 or 10 micrometres) are air pollutants with relatively short lifetimes and therefore exhibit steep gradients in their concentrations, with very high levels (especially for NO2) close to their ambient sources, such as road traffic. This leads to inequalities in air pollution exposure, with people who live closer to traffic and industry sources experiencing far greater exposures than those living in suburban and rural locations. Greater exposure alongside poorer underlying health and social conditions amongst disadvantaged groups combine to generate and exacerbate stark inequalities in health (RCP, 2025).

Regional variations in the relationship between outdoor air pollution and socioeconomic deprivation across the UK are less well understood (Milojevic et al. 2017; Woodward et al. 2024). In addition, individual PM2.5 and PM10 components e.g. inorganic nitrate may exhibit different relationships with socioeconomic indicators (Milojevic et al. 2017) and have differing toxicities that could lead to differences in health risk (Masselot et al. 2022). Systematic inequalities have also been found for indoor air pollution exposure across London and the UK (where indoor sources of air pollution, outdoor ingress, housing characteristics and demographics together lead to differential air pollutant exposures in indoor environments (Ferguson et al; 2021). The health implications of these indoor exposure variations are unclear.

This project will use detailed speciated observations and high-resolution chemistry transport models to improve our understanding of the distributions and inequalities in air pollution exposures regionally across the UK. The project will conduct statistical analysis to link air pollution levels to indices of socioeconomic deprivation and various physical and mental health outcomes to examine the impacts on inequalities. This project will be aligned with a newly UKRI/NIHR-funded UK Hub called “INHABIT: Indoor HABItability during the Transition to Net Zero Housing”. The outcomes of this research will contribute to improved quantitative understanding of inequalities in the health impacts of air pollution.

Research questions

1. What is the relationship between outdoor air pollution and different indicators of socio-economic inequalities for different regions across the UK, including urban-rural status, and how have these changed over recent decades?
2. How does the composition of PM2.5 and PM10 vary, and is there a relationship between particle composition and socio-economic inequalities across the UK?
3. How do health inequalities relating to air pollution exposure vary between different health outcomes?
4. Are the inequalities in the health effects of air pollution greater for indoor than outdoor air pollution?
5. How are these relationships likely to change under future scenarios?

Methodology

The student will use air pollution measurements and chemistry transport model simulations alongside statistical and epidemiological techniques (that could include machine learning) to study the relationships between air pollution exposure and socioeconomic and health inequalities. The student will have the opportunity to be part of a large interdisciplinary team of academics, including postdoctoral researchers and PhD students and government/local authority stakeholders within the INHABIT hub-which has inequalities as its central science theme. They will gain experience of public engagement and links to local authorities and councils.

Air pollution data at high resolution over the UK are available from the EMEP4UK chemistry transport model (Vieno et al. 2016); the student will have the opportunity to set-up and perform their own chemistry transport model simulations. Multiple aerosol species and their governing physical and chemical processes are explicitly represented within EMEP4UK. This enables high resolution estimates of the spatio-temporal variations in the composition of PM2.5 and PM10 to be calculated across the UK. Speciated composition measurements are also available for several UK “supersites” including at Birmingham, Manchester London and Edinburgh. These measurements will be used to perform independent analyses and to evaluate the model performance for different regions. PM will also be collected at supersets on different occasions. The reactivity of the PM will be tested in laboratory toxicology models (e.g. acellular free radical generation) and the results correlated with the detailed chemical profiling data from the supersite monitors.

To quantify inequalities in air pollution exposure and the relationship between exposure and health inequalities, socio-economic and health datasets available at the at the Lower-level Super Output Area (LSOA) will be used to perform statistical and epidemiological analyses. The relationship between exposure and health inequalities will be evaluated and the sensitivity of their results to the choice of health outcome data (e.g. all cause and cause specific mortality, hospital admissions for respiratory health, limiting long-term illness, mental health) will be evaluated.

As the project progresses, indoor air pollution data and related toxicological analyses from INHABIT, for which data collection is underway, will become available, to enable the student to investigate relationships between indoor air pollution and socio-economic and health inequalities. Besides aceullar toxicology, the ability of indoor PM to induce inflammation is being assessed in ongoing studies in INHABIT using mouse models for complimentary analyses.

In year 1, the student will gain familiarity with the different observational and model-derived datasets of outdoor air pollution and its composition and the relevant literature. They will evaluate the suitability of different socio-economic indices and curate different health outcome datasets. Depending on their interests they will also be trained in setting up and performing simulations using the EMEP4UK chemistry transport model.

In year 2, they will continue to develop their statistical skills for data linkage and epidemiological analyses and potentially explore the use of machine learning for data analysis and interpretation. They will explore the spatio-temporal relationships between differential air pollution exposures socio-economic and health inequalities.

In year 3/4, they will further explore air-pollution-socioeconomic-health inequalities focussing on key health outcomes or indicators and extending their analyses to indoor exposures.

Funding Notes

UK home fee status applies. This project is currently only available for UK students. EU students will a strong skill set in the PhD topic may be considered.