Investigating inequalities in NO2 air pollution concentrations on novel indicators relating to small spatial areas – International Journal for Equity in Health

Report on Air Pollution, Health, and Socioeconomic Disparities in the Context of Sustainable Development Goals

Introduction: Air Pollution as a Barrier to Sustainable Development

Air pollution, identified by the World Health Organization (WHO) as a primary environmental health risk, presents a significant challenge to the achievement of the United Nations Sustainable Development Goals (SDGs). Despite a general decline in emissions, exposure to nitrogen dioxide (NO2), primarily from vehicle emissions, remains a critical issue. This directly impacts several SDGs, most notably SDG 3 (Good Health and Well-being) and SDG 11 (Sustainable Cities and Communities).

Regulatory actions, such as the WHO’s 2021 reduction of its annual NO2 guideline to 10 µg/m³ and the EU’s 2024 Ambient Air Quality Directive mandating a limit of 20 µg/m³ by 2030, are policy instruments designed to advance these goals by mitigating the adverse health and environmental impacts of air pollution.

Impacts of Nitrogen Dioxide (NO2) Exposure on Sustainable Development

Undermining SDG 3: Good Health and Well-being

Exposure to NO2 pollution is a direct threat to public health, undermining progress towards SDG 3, which aims to ensure healthy lives and promote well-being for all. The health consequences are severe and widespread:

• Respiratory Illnesses: NO2 irritates airways, aggravating conditions like asthma and leading to coughing, wheezing, and breathing difficulties.
• Increased Mortality: Long-term exposure to NO2 is linked to all-cause mortality and mortality from respiratory conditions such as COPD. In 2021, NO2 exposure above WHO guidelines was estimated to have caused 52,000 premature deaths in the EU-27.
• Chronic Diseases: The burden of disease attributable to NO2 includes diabetes mellitus and stroke.
• Adverse Birth Outcomes: Traffic-related air pollution is associated with low birth weight and premature birth.
• Neurological Disorders: Research has suggested a link between traffic-related pollution and conditions such as autism.

Impeding SDG 8: Decent Work and Economic Growth

The economic repercussions of air pollution hinder the attainment of SDG 8 by imposing significant costs on society and reducing economic productivity. These impacts include:

• Increased Healthcare Costs: In Ireland, the annual cost of treating stroke and asthma cases attributable to NO2 pollution is estimated at nearly €2.7 million and €0.4 million, respectively.
• Reduced Productivity: Poor air quality leads to lower productivity through employee absenteeism and reduced life expectancy.

Environmental Inequality and the Challenge to SDG 10: Reduced Inequalities

The Principle of Environmental Justice and SDG 10

The unequal distribution of environmental burdens like air pollution is a critical issue of social inequality, directly challenging the principles of SDG 10 (Reduced Inequalities). Environmental justice seeks to ensure that no group of people, particularly marginalized or vulnerable populations, bears a disproportionate share of negative environmental consequences. Socially and economically disadvantaged groups often face a “triple jeopardy,” where higher exposure to pollutants coincides with higher baseline rates of disease and reduced access to healthcare, exacerbating health disparities.

Disproportionate Exposure Among Vulnerable Populations

Socioeconomic factors often determine exposure levels, creating patterns of environmental inequality that contravene the goals of SDG 10.

• Socioeconomically disadvantaged populations may live in areas with higher NO2 concentrations due to lower property values near major transport routes.
• Studies have shown that schools in disadvantaged areas are often exposed to higher levels of NO2 pollution.
• Vulnerable groups with pre-existing health conditions or poorer access to healthcare are more susceptible to the negative health effects of air pollution.

Analysis of NO2 Exposure: International and National Perspectives

Global Research on Environmental Inequality

International studies reveal complex and often inequitable patterns of NO2 exposure, highlighting the global relevance of this challenge to SDG 10.

1. United States & United Kingdom: Research consistently finds that more vulnerable communities, including racial minorities and lower-income groups, are disproportionately exposed to higher levels of NO2 pollution.
2. Continental Europe: Findings are more heterogeneous. While some studies associate lower socioeconomic position with higher NO2 exposure, others in cities like Paris and Copenhagen have found the opposite, with affluent city-center districts recording high pollution levels.
3. Australia: Research indicates that higher NO2 exposure is experienced by ethnic minority groups and socioeconomically disadvantaged residents in urban areas.

The Irish Context: A Case Study for SDG Monitoring

Ireland provides a valuable case study for examining NO2 pollution in a country with generally clean air but concentrated urban pollution hotspots. This research addresses a critical data gap by conducting the first national study of NO2 at a small geographical area, aligning with the data and monitoring objectives of SDG 17 (Partnerships for the Goals).

• Previous Irish studies have linked poor air quality in Dublin to increased hospital admissions for asthma, COAD, and heart failure.
• This study distinguishes itself by using high-resolution NO2 data (2010-2020) combined with recent 2022 census information on socioeconomic position and health.
• The analysis of NO2 concentrations against indicators like housing tenancy and smoking rates provides new quantitative data on environmental inequality, essential for targeted policymaking.

Contribution to the Sustainable Development Agenda

Informing Evidence-Based Policy for SDG Attainment

This research provides a high-resolution, national-level analysis of NO2 exposure, offering critical insights for developing policies to achieve multiple SDGs. By documenting patterns of environmental inequality, the findings can help governmental and environmental bodies create more effective and equitable strategies to reduce air pollution. The study’s detailed analysis supports progress towards:

• SDG 3 (Good Health and Well-being): By identifying populations at higher risk from NO2 exposure, enabling targeted public health interventions.
• SDG 10 (Reduced Inequalities): By providing clear evidence of disparities in environmental burdens, which is the first step toward rectifying them.
• SDG 11 (Sustainable Cities and Communities): By offering data to inform sustainable urban planning, transport policy, and air quality management to create healthier and more equitable cities.
• SDG 16 (Peace, Justice and Strong Institutions): By contributing to a transparent evidence base that can support fairer and more just decision-making processes regarding environmental policy.

1. Which SDGs are addressed or connected to the issues highlighted in the article?

SDG 3: Good Health and Well-being

• The article extensively discusses the severe health consequences of air pollution, specifically Nitrogen Dioxide (NO₂). It states that NO₂ exposure aggravates respiratory diseases, leading to “coughing, wheezing, and difficulty breathing.” The article also links long-term exposure to mortality, citing that it is “at least as important as that of PM_2.5.” It quantifies the impact by mentioning that in 2021, NO₂ levels exceeding WHO recommendations caused an estimated “52,000 premature deaths in the EU-27.” Furthermore, it connects traffic-related air pollution to “poorer birth outcomes, such as, low birth weight and premature birth,” directly aligning with the goal of ensuring healthy lives.

SDG 10: Reduced Inequalities

• A central theme of the article is the unequal distribution of air pollution’s burdens. It highlights “social inequalities of air quality” and notes that “socioeconomically disadvantaged or vulnerable populations (e.g., lower-income households) may live in areas with higher NO₂ concentrations.” The article explores the concepts of “environmental equity” and “environmental justice,” pointing out that spatial inequalities place “disproportionate health risks on people who are already the most vulnerable.” This focus on how marginalized groups are more severely affected by environmental hazards is a core component of SDG 10.

SDG 11: Sustainable Cities and Communities

• The article focuses on air pollution within urban and populated areas, identifying NO₂ as a “gaseous pollutant from burning petrol or diesel in vehicles.” It discusses pollution “hotspots” in urban environments and the challenges they present. The article’s analysis of NO₂ concentrations at a “small geographical area” level, particularly in relation to traffic and housing, directly addresses the need to improve urban air quality. The mention of the EU’s “Ambient Air Quality Directive” and its mandate for Member States to achieve specific air quality levels by 2030 underscores the connection to making cities and human settlements inclusive, safe, resilient, and sustainable.

2. What specific targets under those SDGs can be identified based on the article’s content?

SDG 3: Good Health and Well-being

• Target 3.9: By 2030, substantially reduce the number of deaths and illnesses from hazardous chemicals and air, water and soil pollution and contamination.
  • The article directly supports this target by detailing the health impacts of NO₂ air pollution. It mentions that the “mortality burden of disease attributable to NO₂ includes diabetes mellitus, stroke and asthma” and cites an estimate of “52,000 premature deaths in the EU-27” due to NO₂ exposure. The entire study is premised on understanding and mitigating the health risks associated with this specific form of air pollution.

SDG 10: Reduced Inequalities

• Target 10.2: By 2030, empower and promote the social, economic and political inclusion of all, irrespective of age, sex, disability, race, ethnicity, origin, religion or economic or other status.
  • The article’s investigation into how “more vulnerable communities, particularly those comprised of racial minorities and lower income groups, are more likely to be exposed to higher NO₂ pollution levels” aligns with this target. By analyzing environmental inequality and the “triple jeopardy” where the most vulnerable face the highest exposure, the research aims to provide data that can inform policies to create a more equitable distribution of environmental burdens, thereby promoting social inclusion.

SDG 11: Sustainable Cities and Communities

• Target 11.6: By 2030, reduce the adverse per capita environmental impact of cities, including by paying special attention to air quality and municipal and other waste management.
  • This target is directly addressed through the article’s focus on urban air quality. The text explicitly mentions the WHO’s updated annual average NO₂ guideline (from 40 µg/m³ to 10 µg/m³) and the EU’s 2024 Ambient Air Quality Directive, which “mandates Member States to achieve a maximum annual average of 20 µg/m³ by 2030.” These policy measures and scientific guidelines are central to reducing the adverse environmental impact of cities by improving air quality.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

Indicators for SDG 3 and SDG 11

• Annual mean concentration of Nitrogen Dioxide (NO₂): This is a primary indicator used throughout the article to measure air quality. It is directly related to SDG Target 11.6. The article provides specific quantitative benchmarks that can be used to track progress, such as the WHO’s new guideline of 10 µg/m³ and the EU’s 2030 target of 20 µg/m³. This metric serves as a direct measure of air pollution levels.
• Mortality and morbidity rates attributable to air pollution: This indicator is relevant to SDG Target 3.9. The article implies its use by citing statistics on the health burden of NO₂, including the “52,000 premature deaths in the EU-27” and the association of NO₂ with “diabetes mellitus, stroke and asthma.” Tracking the number of deaths, hospital admissions (for conditions like asthma and COPD), and cases of specific diseases linked to NO₂ would measure progress in reducing the health impacts of air pollution.

Indicators for SDG 10

• Disaggregation of air pollution exposure data by socioeconomic and demographic factors: While not a formal UN indicator, this is strongly implied as the core methodology of the study. The article criticizes the lack of “small area level data to examine the social inequalities of air quality” and aims to fill this gap by linking NO₂ data with “indicators of socioeconomic position and health, such as housing tenancy and smoking status.” Therefore, measuring the differential in NO₂ exposure levels between high-income and low-income areas, or across different demographic groups, serves as a direct indicator of environmental inequality and progress towards Target 10.2.

4. Table of SDGs, Targets, and Indicators

Source: equityhealthj.biomedcentral.com