A breath of fresh air: understanding the impact of air pollution on public health

Research summary

This programme of research comprises a series of projects which represent the first large-scale study of the health effects of outdoor air pollution in Northern Ireland (NI). The World Health Organisation (WHO) has identified outdoor air pollution as a top environmental risk factor for mortality and disease globally, while long-term exposure to the most damaging form of pollution, fine particulate matter, has been linked to 28,000-36,000 deaths per year in the UK. This project provides policymakers in NI (and further afield) with unique and timely empirical evidence to inform decision-making around future air pollution mitigation policies, particularly in anticipation of the NI’s first Clean Air Strategy, expected to undergo its next consultation phase in 2025.

Data used

The project uses various individual-level administrative datasets linked to area-level pollution data. This includes the Northern Ireland Longitudinal Study (NILS) linked to the Enhanced Prescribing Database (EPD), which matches anonymised Census and vital events information to records of prescriptions dispensed by General Practices. Another is the Northern Ireland Maternity Services (NIMATs) dataset, which contains information about infants and mothers for all pregnancies that take place in NI hospitals. These datasets were merged with annual 1x1km grid square air pollution concentration data published by the Department for Environment, Food and Rural Affairs (DEFRA). All data are analysed by the research team in Trusted Research Environments under strict privacy standards.

Methods used

Statistical techniques are used to assess whether air pollution exposure is linked to adverse health outcomes, including adult self-reported health, receipt of prescriptions to treat certain health conditions, and measures of infant health including birthweight. In particular, regression analysis is used to separate the impact of air pollution exposure from the impact of other factors which contribute to poor health, such as area-level socioeconomic deprivation. Where possible, cutting-edge techniques are employed to identify causal effects, vital for policymakers seeking to quantify the potential public health benefits of reducing pollution.

Research findings

The findings show that long-term exposure to fine particulate matter is associated with (and likely to be causally related to) a range of negative self-reported health outcomes among adults, including chronic illness, poor general health, breathing difficulties, mobility difficulties, and deafness. However, analysis of the NIMATs data does not find a link between exposure during pregnancy and adverse infant health outcomes such as low birth weight or pre-term birth. Analysis of the mortality burden suggests that approximately 900 annual premature deaths in NI may be attributed to long-term fine particulate matter exposure, and that reducing pollution to the WHO guideline level could reduce this figure by 400 premature deaths every year. Ongoing research is exploring the links between childhood exposure and respiratory ill-health, and long-term exposure and the onset of Parkinson’s disease and dementia.

Research impact

The project team produced an interactive online map which takes advantage of the linkage between the NILS and DEFRA’s finely grained air pollution data. This allows users to explore air pollution levels across NI and empowers decisionmakers to identify hotspot areas where the health burdens are likely to be greatest and where resources ought to be targeted. This freely available dashboard has received press attention and been cited in a response to a Belfast city traffic consultation and in other communications with government officials.

A policy briefing describing the key messages of the research has been shared with DAERA officials drafting the Clean Air Strategy for Northern Ireland. The research findings have also informed the project team’s responses to other consultations, including the UK Government’s national air quality targets consultation, DAERA’s Draft Environment Strategy, and the latest NI Executive Draft Programme for Government consultation.

Members of the project team met with then-Agriculture Minister Edwin Poots MLA and his officials, alongside British Lung Foundation (now Asthma + Lung UK), to discuss the impact of poor air quality on health in NI.

Research findings have been presented to All Party Groups (APG) on both Lung Health and Climate Action, allowing the team to engage directly with members of the Legislative Assembly and the public at large. Further follow-up with Paula Bradshaw MLA, chair of the APG on Lung Health, led to her submitting an Assembly Written Question regarding bridging legislation from the Digital Economy Act to allow the sharing and linkage of health data to other administrative Data in Northern Ireland. 

A report assessing the mortality burden of air pollution on the island of Ireland has been cited in national press, in responses to the NI Executive Draft Programme for Government consultation, and in other communications with government officials.

Research outputs

Publications and reports

• Peer-reviewed articles in Economics and Human Biology and Health Economics.
• ADR Policy Briefing
• ADR Data Insight
• Report on the mortality burden of air pollution on the island of Ireland
• Air Pollution in Northern Ireland dashboard

Engagement events

A public symposium was held at Queen’s University Belfast in October 2022 showcasing research findings to stakeholders, including officials in government departments, representatives of third-sector organisations, politicians, academics, and the general public. The project steering group, which helps to inform the research and provides invaluable feedback on the findings, includes representatives of the Department for Agriculture, Environment and Rural Affairs (DAERA), Belfast City Council, Department of Health (NI), Asthma + Lung UK NI, British Heart Foundation NI, Alzheimer’s Society, and the South Eastern Health and Social Care Trust. This group is very active and has met six times since the project’s inception.

Blogs, news reports and videos

This research has informed commentary in local news media, including an opinion piece in the Belfast Telegraph and radio and television interviews on BBC NI.

Presentations and awards

Research findings have been presented at All Party Groups on both Lung Health and Climate Action, the Northern Ireland Environment Forum, the Westminster Commission for Road Air Quality Emissions Reduction Workshop, and other events including academic conferences, workshops, and a party conference. One member of the project team, Dr Neil Rowland, was awarded the honorary role of UKRI Regional Clean Air Champion for Northern Ireland in 2021 as part of the Clean Air Programme.

Acknowledgements

The authors would like to acknowledge the help provided by the staff of the Honest Broker Service (HBS) within the Business Services Organisation Northern Ireland (BSO).  The HBS is funded by the BSO and the Department of Health (DoH).  The authors alone are responsible for the interpretation of the data and any views or opinions presented are solely those of the author and do not necessarily represent those of the BSO.

The help provided by the staff of the Northern Ireland Longitudinal Study (NILS) and the NILS Research Support Unit is acknowledged.  The NILS is funded by the Health and Social Care Research and Development Division of the Public Health Agency (HSC R&D Division) and NISRA.  The NILS-RSU is funded by the ESRC and the Northern Ireland Government. The authors alone are responsible for the interpretation of the data and any views or opinions presented are solely those of the author and do not necessarily represent those of NISRA/NILS.

Administrative Data Research Northern Ireland (ADR-NI) funding gratefully acknowledged.