Urban areas are highly complex systems. Solutions to urban problems are often co-dependent and inter-connected. How can a systems approach to cities improve sustainability and health outcomes?

Cities face key global and local sustainability challenges such as a changing climate, air pollution, and waste, all of which also present risks for human health. Improving urban sustainability can provide co-benefits for public health. However the effectiveness – or unintended consequences – of policies or actions can depend on the behaviours and relationships in the wider urban system.

Guest editors: Jonathon Taylor and Philippa Howden-Chapman

Given the imperative that cities reduce their environmental footprints and increase their resilience to environmental change, they have a significant role in protecting and promoting planetary health. At the same time, rapid urbanisation is occurring, often with little attention paid to the sustainability of such growth. Sustainability and public health in existing cities and districts can suffer from lock-in created by the built environment and infrastructure.

This special issue provides new evidence on the connections between the diverse components (e.g. city governance, economy, welfare systems, housing, education, working environments, urban density, ‘green’ infrastructure and open space, transport, waste management, water and sanitation, air quality, health systems) comprising urban systems and how they inhibit or promote public health, wellbeing and equity as well as planetary health. Emphasis is placed on the roles and connections between different elements of the urban system.

The papers also provide insights into how best to use this research evidence to inform decision-makers and the public about the pathways of development that provide the greatest opportunities for health and sustainability, and to track progress towards the fulfilment of agreed goals. By moving from a siloed approach towards a broader systemic understanding, there are significant opportunities to develop and implement evidence-based solutions that have the potential to lead to significant improvements in sustainability and health.

Some of the key contributors to urban health problems are environmental burdens and these, like other determinants of health, are often unequally distributed. Reducing environmental burdens requires a set of policies that address the wider systemic causes of exposures. Implementing these policies raises important questions about who oversees them, how the responsibility is distributed, how unintended consequences are avoided and how progress is measured.

Table of Contents

The significance of urban systems on sustainability and public health [editorial]
J. Taylor & P. Howden-Chapman

COVID-19 mobility restrictions: impacts on urban air quality and health
N. Mohajeri, A. Walch, A. Gudmundsson, C. Heaviside, S. Askari, P. Wilkinson & M. Davies

Systemic inequalities in indoor air pollution exposure in London, UK
L. Ferguson, J. Taylor, K. Zhou, C. Shrubsole, P. Symonds, M. Davies & S. Dimitroulopoulou

Does reframing urban policy around wellbeing support carbon mitigation?
R. Chapman & P. Howden-Chapman

Relationship-building around a policy decision-support tool for urban health
C. Deloly, A. Roué-Le Gall, G. Moore, L. Bretelle, J. Milner, N. Mohajeri, D. Osrin, G. Salvia, P. Symonds, I. Tsoulou, N. Zimmermann, P. Wilkinson & M. Davies

Evidence-informed urban health and sustainability governance in two Chinese cities
H. Pineo, K. Zhou, Y. Niu, J. Hale, C. Willan, M. Crane, N. Zimmermann, S. Michie & Q. Liu

A multi-scalar perspective on health and urban housing: an umbrella review
C. Turcu, M. Crane, E. Hutchinson, S. Lloyd, K. Belesova, P. Wilkinson & M. Davies

Climate change projections for sustainable and healthy cities
C. Goodess, S. Berk, S.B. Ratna, O. Brousse, M. Davies, C. Heaviside, G. Moore & H. Pineo

Empowered by planning law: unintended outcomes in the Helsinki region
A. Joutsiniemi, M. Vaattovaara & J. Airaksinen

Unidirectional pedestrian circulation: physical distancing in informal settlements
J. Fernandez Gonzalez & A. Gongal

Dhaka landfill waste practices: addressing urban pollution & health hazards
S.A. Urme, M.A. Radia, R. Alam, M.U. Chowdhury, S. Hasan, S. Ahmed, H.H. Sara, M.S. Islam, D.T. Jerin, P.S. Hema, M. Rahman, A.K.M.M. Islam, M.T. Hasan & Z Quayyam

Abstracts

The significance of urban systems on sustainability and public health [editorial]
J. Taylor & P. Howden-Chapman
https://doi.org/10.5334/bc.181

Urban areas are highly complex systems, with interconnections between their political, economic, social, natural and built environments components, and each with its own unique priorities and contexts. They are also facing key global and local sustainability challenges such as a changing climate, air pollution and waste, all of which also present risks for population health. Improving urban sustainability can provide co-benefits for population health; however, the effectiveness—or unintended consequences—of policies or actions can depend on the behaviours and relationships in the wider urban system. The papers published in this special issue explore issues related to urban sustainability and health, including urban design and environmental justice, scale, and informal settlements. The papers also describe issues at the interface of different system components, demonstrating the systemic challenges that can act to enhance or prevent sustainable change. The complexity of urban environments presents challenges for research and policy, both of which can be reductive, and conducted independent from other disciplines or government departments. However, by moving from this siloed approach towards a broader systemic understanding, there are opportunities to develop and implement evidence-based solutions that have the potential to lead to significant improvements in sustainability and health.

COVID-19 mobility restrictions: impacts on urban air quality and health
N. Mohajeri, A. Walch, A. Gudmundsson, C. Heaviside, S. Askari, P. Wilkinson & M. Davies
https://doi.org/10.5334/bc.124

In 2020, Covid-19-related mobility restrictions resulted in the most extensive human-made air-quality changes ever recorded. The changes in mobility are quantified in terms of outdoor air pollution (concentrations of PM_2.5 and NO₂) and the associated health impacts in four UK cities (Greater London, Cardiff, Edinburgh and Belfast). After applying a weather-corrected machine learning (ML) technique, all four cities show NO₂ and PM_2.5 concentration anomalies in 2020 when compared with the ML-predicted values for that year. The NO₂ anomalies are –21% for Greater London, –19% for Cardiff, –27% for Belfast and –41% for Edinburgh. The PM_2.5 anomalies are 7% for Greater London, –1% for Cardiff, –15% for Edinburgh, –14% for Belfast. All the negative anomalies, which indicate air pollution at a lower level than expected from the weather conditions, are attributable to the mobility restrictions imposed by the Covid-19 lockdowns. Spearman rank-order correlations show a significant correlation between the lowering of NO₂ levels and reduction in public transport (p < 0.05) and driving (p < 0.05), which is associated with a decline in NO₂-attributable mortality. These positive effects of the mobility restrictions on public health can be used to evaluate policies for improved outdoor air quality.

Policy relevance: Finding the means to curb air pollution is very important for public health. Empirical evidence at a city scale reveals significant correlations between the reduction in vehicular transport and in ambient NO₂ concentrations. The results provide justification for city-level initiatives to reduce vehicular traffic. Well-designed and effective policy interventions (e.g. the promotion of walking and cycling, remote working, local availability of services) can substantially reduce long-term air pollution and have positive health impacts.

Systemic inequalities in indoor air pollution exposure in London, UK
L. Ferguson, J. Taylor, K. Zhou, C. Shrubsole, P. Symonds, M. Davies & S. Dimitroulopoulou
http://doi.org/10.5334/bc.100

Deprived communities in many cities are exposed to higher levels of outdoor air pollution, and there is increasing evidence of similar disparities for indoor air pollution exposure. There is a need to understand the drivers for this exposure disparity in order to develop effective interventions aimed at improving population health and reducing health inequities. With a focus on London, UK, this paper assembles evidence to examine why indoor exposure to PM_2.5, NO_x and CO may disproportionately impact low-income groups. In particular, five factors are explored, namely: housing location and ambient outdoor levels of pollution; housing characteristics, including ventilation properties and internal sources of pollution; occupant behaviours; time spent indoors; and underlying health conditions. Evidence is drawn from various sources, including building physics models, modelled outdoor air pollution levels, time–activity surveys, housing stock surveys, geographical data, and peer-reviewed research. A systems framework is then proposed to integrate these factors, highlighting how exposure to high levels of indoor air pollution in low-income homes is in large part due to factors beyond the control of occupants, and is therefore an area of systemic inequality.

Policy relevance: There is increasing public and political awareness of the impact of air pollution on public health. Strong scientific evidence links exposure to air pollution with morbidity and mortality. Deprived communities may be more affected, however, with limited evidence on how deprivation may influence their personal exposure to air pollution, both outdoors and indoors. This paper describes different factors that may lead to low-income households being exposed to higher levels of indoor air pollution than the general population, using available data and models for London (i.e. living in areas of higher outdoor air pollution, in poor-quality housing, undertaking more pollution-generating activities indoors and spending more time indoors). A systems approach is used to show how these factors lead to systemic exposure inequalities, with low-income households having limited opportunities to improve their indoor air quality. This paper can inform actions and public policies to reduce environmental health inequalities, considering both indoor and outdoor air.

Does reframing urban policy around wellbeing support carbon mitigation?
R. Chapman & P. Howden-Chapman
http://doi.org/10.5334/bc.115

New Zealand (‘Aotearoa’) is a highly urbanised country with one of the first governments in the world to adopt a wellbeing budget framework. That framework, in combination with the architecture for decarbonisation provided by New Zealand’s 2019 ‘Zero Carbon’ Act, means there are now institutional and policy incentives in place, and developing incrementally, to combine the pursuit of wellbeing and decarbonisation. These incentives also align with the outcomes highlighted in the United Nations’ Sustainable Development Goals (SDGs). This paper considers the way policy and institutional approaches to carbon mitigation are being linked to wellbeing in three interconnected urban, non-agricultural domains responsible for much of New Zealand’s carbon emissions: building, urban form and transport. Looking beyond the current Covid-19 recovery process, emerging evidence is presented to ascertain whether the wellbeing-focused policy approach, with its associated attention to co-benefits, is creating a clear institutional refocusing. In addition, other evidence suggests that New Zealanders see health and wellbeing as improving, at the same time as the country is moving towards the net zero carbon emissions target.

Policy relevance: In New Zealand, a new emphasis by the government on wellbeing now provides a powerful policy framing. At the same time, attention to the critical issue of climate change is strongly influencing many aspects of public policy. This paper investigates, for three related economic domains—building, urban form and transport—how the new framing is being manifested in institutions and policy. Attention to co-benefits, highlighting elements of wellbeing, appears to be shifting the policy debate away from economic growth towards a richer set of concerns more relevant to an era in which managing environmental, social and health crises (such as Covid-19), decarbonisation, and housing affordability are more prominent. The paper also outlines a new research programme that measures outcomes from a set of major public housing and urban regeneration investments in terms of wellbeing metrics.

Relationship-building around  a policy decision-support tool for urban health
C. Deloly, A. Roué-Le Gall, G. Moore, L. Bretelle, J. Milner, N. Mohajeri, D. Osrin, G. Salvia, P. Symonds, I. Tsoulou, N. Zimmermann, P. Wilkinson, & M. Davies
https://doi.org/10.5334/bc.110

Contemporary challenges linked to public health and climate change demand more effective decision-making and urban planning practices, in particular by taking greater account of evidence. In order to do this, trust-building relationships between scientists and urban practitioners through collaborative research programmes is required. Based on a policy-relevant research project, Complex Urban Systems for Sustainability and Health (CUSSH), this project aims to support the transformation of cities to meet environmental imperatives and to improve health with a quantitative health impact assessment. A case study in Rennes, France, focuses on the role of a policy decision-support tool in the production and use of knowledge to support evidence-informed decision-making. Although the primary objective of informing decision-making through evidence-based science is not fulfilled, the use of a decision-making support tool can lay the foundations for relationship-building. It can serve as a support for boundary-spanning activities, which are recognised for their effectiveness in linking science to action. This case study illustrates that the path of knowledge transfer from science to policy can be challenging, and the usefulness of using models may not be where it was thought to have been.

Practice relevance: The requirements for an effective policy-relevant research programme depend on the establishment of trust. An analysis of the evolution of relationships between cities’ practitioners and scientists shows the need to establish relationships between stakeholders involved in this kind of research. Even if it does not directly support the implementation of transformational policies for health and sustainability, the use of a decision-making support tool can become essential in building trust relationships and later have ripple effects to achieve its primary goals. Moreover, a dedicated team has a key role to facilitate the links between scientists and cities practitioners—to boundary span. Finally, this paper adds to a growing body of work reflecting upon the success of policy–research partnerships.

Evidence-informed urban health and sustainability governance in two Chinese cities
H. Pineo, K. Zhou, Y. Niu, J. Hale, C. Willan, M. Crane, N. Zimmermann, S. Michie & Q. Liu
http://doi.org/10.5334/bc.90

Sustainable development is best supported by intersectoral policies informed by a range of evidence and knowledge types (e.g. scientific and lay). Given China’s rapid urbanisation, scale and global importance in climate mitigation, this study investigates how evidence is perceived and used to inform urban health and sustainability policies at central and local levels. Well-informed senior professionals in government/scientific agencies (12 in Beijing and 11 in Ningbo) were interviewed. A thematic analysis is presented using deductive and inductive coding. Government agency participants described formal remits and processes determining the scope and use of evidence by different tiers of government. Academic evidence was influential when commissioned by government departments. Public opinion and economic priorities were two factors that also influenced the use or weight of evidence in policymaking. This study shows that scientific evidence produced or commissioned by government was routinely used to inform urban health and sustainability policy. Extensive and routine data collection is regularly used to inform cyclical policy processes, which improves adaptive capacity. This study contributes to knowledge on the ‘cultures of evidence use’. Environmental governance can be further improved through increased data-sharing and use of diverse knowledge types.

Policy relevance:

• Insights are provided into the ‘cultures of evidence use’ in urban sustainability and health governance in two Chinese cities, noting the complex interconnections between national policy agendas, the public and evidence. Policies are centrally led and informed by officially commissioned scientific evidence.
• Environmental health data were used for monitoring policy implementation, and they were interpreted with careful consideration of public opinion and economic priorities.
• There were opportunities for local priorities to shift the policy agenda, particularly when the public became aware of a specific environmental health threat.
• Environmental governance could be strengthened in these settings through increased cross-sector data-sharing and integration of diverse knowledge types.
• A strength of China’s approach is routine data collection that feeds a monitoring and policy cycle rarely achieved elsewhere. This cycle provides feedback to government departments, allows policy adjustment over time and can inform decisions during crises.

A multi-scalar perspective on health and urban housing: an umbrella review
C. Turcu, M. Crane, E. Hutchinson, S. Lloyd, K. Belesova, P. Wilkinson & M. Davies
https://doi.org/10.5334/bc.119

With more than half the world’s population living in cities, understanding how the built environment impacts human health at different urban scales is crucial. To be able to shape cities for health, an understanding is needed of planetary health impacts, which encompass the human health impacts of human-caused disruptions on the Earth’s natural ecosystems. This umbrella review maps health evidence across the spatial scales of the built environment (building; neighbourhood; and wider system, including city, regional and planetary levels), with a specific focus on urban housing. Systematic reviews published in English between January 2011 and December 2020 were searched across 20 databases, with 1176 articles identified and 124 articles screened for inclusion. Findings suggests that most evidence reports on health determinants at the neighbourhood level, such as greenspace, physical and socio-economic conditions, transport infrastructure and access to local services. Physical health outcomes are also primarily reported, with an emerging interest in mental health outcomes. There is little evidence on planetary health outcomes and significant gaps in the research literature are identified. Based on these findings, three potential directions are identified for future research.

Policy relevance: Evidence about local built environment determinants of health have focused to date on physical health outcomes and the neighbourhood level; there is also significant evidence about mental health outcomes and greenspace. Future research can strengthen understanding of mental health outcomes across all scales and determinants of the built environment; investigate more robustly planetary health outcomes; and provide additional evidence at the building and wider urban system level, especially in relation to low-income settings, vulnerable groups and communicable disease. There is limited discussion of implications for policymaking and economic evaluations of health interventions, i.e. the cost of intervention versus health outcomes. Urban health interventions have focused to date on treating the effects of health conditions; however, there is potential for constructive interventions in the built environment (at various scales) which improve health and/or reduce environmental health risks if the policy focus is on dealing with the causes of health conditions.

Climate change projections for sustainable and healthy cities
C. Goodess, S. Berk, S.B. Ratna, O. Brousse, M. Davies, C. Heaviside, G. Moore & H. Pineo
https://doi.org/10.5334/bc.111

The ambition to develop sustainable and healthy cities requires city-specific policy and practice founded on a multidisciplinary evidence base, including projections of human-induced climate change. A cascade of climate models of increasing complexity and resolution is reviewed, which provides the basis for constructing climate projections—from global climate models with a typical horizontal resolution of a few hundred kilometres, through regional climate models at 12–50 km to convection-permitting models at 1 km resolution that permit the representation of urban induced climates. Different approaches to modelling the urban heat island (UHI) are also reviewed—focusing on how climate model outputs can be adjusted and coupled with urban canopy models to better represent UHI intensity, its impacts and variability. The latter can be due to changes induced by urbanisation or to climate change itself. City interventions such as greater use of green infrastructure also have an effect on the UHI and can help to reduce adverse health impacts such as heat stress and the mortality associated with increasing heat. Examples for the Complex Urban Systems for Sustainability and Health (CUSSH) partner cities of London, Rennes, Kisumu, Nairobi, Beijing and Ningbo illustrate how cities could potentially make use of more detailed models and projections to develop and evaluate policies and practices targeted at their specific environmental and health priorities.

Practice relevance: Large-scale climate projections for the coming decades show robust trends in rising air temperatures, including more warm days and nights, and longer/more intense warm spells and heatwaves. This paper describes how more complex and higher resolution regional climate and urban canopy models can be combined with the aim of better understanding and quantifying how these larger scale patterns of change may be modified at the city or finer scale. These modifications may arise due to urbanisation and effects such as the UHI, as well as city interventions such as the greater use of grey and green infrastructures. There is potential danger in generalising from one city to another—under certain conditions some cities may experience an urban cool island, or little future intensification of the UHI, for example. City-specific, tailored climate projections combined with tailored health impact models contribute to an evidence base that supports built environment professionals, urban planners and policymakers to ensure designs for buildings and urban areas are fit for future climates.

Empowered by planning law: unintended outcomes in the Helsinki region
A. Joutsiniemi, M. Vaattovaara & J. Airaksinen
https://doi.org/10.5334/bc.116

What are the unintended outcomes produced by Finland’s planning system? This analysis of present-day planning in Finland addresses how positive aims and promised designs and plans are diluted by the planning process. It shows how changes in the legislation governing planning are empowering the role of institutional needs rather than fostering the desired outcomes. Three levels are analysed: the development and crucial boundary conditions of planning-related legislation; the structure of urban development within the region; and a case study of the 30-year development of an orbital light-rail project. In contrast to claims in the planning literature, the communicative turn has not led to clear positive changes in the process and implementation. This research shows how institutional stakeholders are empowered in current planning practice. The attempt to make planning more inclusive and participatory has paradoxically led into the empowerment of institutional players. The actual outcomes of the planning process are side-tracked, and the evaluation is outsourced in the process, which calls into question the legitimacy of planning actions. There is a need for planning-related studies to address the legislative boundaries and the concrete outputs of the planning process.

Practice relevance: The implementation of the participatory planning ideal in Finland’s planning administration is examined for practical outcomes. By analysing the changes in the legislative framework of planning in its historical context, it is shown that the resulting planning apparatus is no less mechanistic or more open than its earlier forms. Instead, its new comprehensiveness renders it more complicated. Based on the analysis of the development of the legislation, combined with case studies, it is clear that the progress and direction of systemic change has not fulfilled its stated aims. This study shows that the major focus in the development of the planning system is at the level of input legitimacy. Apparent changes are the increased number of stakeholders and unintended complexity of the planning process. All this has been fostered by the changes in the planning law. Regardless of goodwill, the planning outcome is even less predictable and more dominated by power relations than before.

Unidirectional pedestrian circulation: physical distancing in informal settlements
J. Fernandez Gonzalez & A. Gongal
http://doi.org/10.5334/bc.113

The COVID-19 pandemic has resulted in a wide range of spatial interventions to slow the spread of the virus. The spatial limitations of narrow public circulation spaces within informal settlements, which house over 1 billion people around the world, make it impossible for pedestrians to practice physical distancing (or social distancing). A flexible mathematical method, the Cluster Lane Method, is proposed for turning a planar circulation network of any size or complexity into a network of unidirectional lanes. This makes physical distancing possible in narrow circulation spaces by limiting face-to-face interactions. The opportunities and challenges are discussed for the implementation of this cost-efficient, low-tech solution. New notions and theorems are introduced for oriented graphs in graph theory.

Policy relevance: A new approach based on graph theory is used to address the problem of COVID-19 contagion in the narrow public circulation networks of informal settlements. The Cluster Lane Method shows how to convert a planar circulation network of any size or complexity into a network of unidirectional lanes. This makes physical distancing possible in narrow circulation spaces by limiting face-to-face interactions between pedestrians. By involving the inhabitants of the informal settlement throughout the process, more adequate orientations of the lanes can be found.

Dhaka landfill waste practices: addressing urban pollution & health hazards
S.A. Urme, M.A. Radia, R. Alam, M.U. Chowdhury, S. Hasan, S. Ahmed, H.H. Sara, M.S. Islam, D.T. Jerin, P.S. Hema, M. Rahman, A.K.M.M. Islam, M.T. Hasan & Z Quayyam
http://doi.org/10.5334/bc.108

Two Dhaka, Bangladesh, landfills are explored to understand how management practices impact environmental quality and public health in the surrounding areas. A combination of research methods is used, such as geospatial buffer zone analysis, semi-structured observation checklist and qualitative interviews, to gain an understanding of the waste transportation, leachate percolation, and adverse health and environmental effects. A multi-ring buffer zone and ground truth method were applied through ArcMap for the spatial distribution of landfill-adjacent environmental features. Qualitative interviews were conducted with landfill officials and nearby residents. Findings reveal that landfills are situated very close to residential areas, water bodies and agricultural lands, exposing them to various health and environmental hazards. Improper solid waste management practices of the landfills cause adverse environmental effects by leachate percolation, waste incineration and vector breeding. Adjacent dwellers suffer from bronchial diseases, pneumonia, diarrhoea, itching problems, headache and appetite loss. The existing solid waste management system requires managerial and technical modifications to reduce the associated environmental pollution and health hazards.

Practice relevance: Waste management practices impact directly on environmental and public health. Dhaka’s existing waste management practices can become better organised to address these concerns. Source waste reduction must be implemented to ensure the reduction of disposed waste at landfills. Administrative capacity of landfills requires improvement to ensure proper waste management procedures. Increased awareness is also needed among the general population and waste handlers about the adverse effects of uncontrolled waste dumping, along with enforcement measures for improper waste practices. Application of a low-tech, simple and innovative method to improve the leachate treatment process is also needed. Environmentally friendly treatments should be considered in order to minimise landfill odour. Regular training programmes and monitoring activities are needed to ensure the proper utilisation of comfortable and convenient safety gear and reduce vector breeding.

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