Michael Davies

Shaping cities for health: complexity and the planning of urban environments in the 21st century

3·4 billion people—about half the world’s population--live in urban areas, and this number might rise to 6·3 billion by 2050.1 The proportion of the global population living in cities will be 60% by 2030,2 a 72% increase in 30 years (figures 1 and u200band2).2). Urban growth will be greatest in Africa and Asia, followed by Latin America and Oceania.5 Even in long-established urban areas in Europe, urban population growth during that period will reach almost 5%.5 This growth will not only result in more megacities (cities of more than 10 million people), increasingly concentrated in Asia, but also in more medium-sized cities, especially in Africa. UN estimates are that about 1 billion people, nearly a sixth of the global population, live in slum-like conditions. With the worldwide population predicted to expand to 9 billion by 2030, the number of people living in slum-like conditions could reach 2 billion.5 n n n nFigure 1 n nWorld population growth, 1950-2050 n n n n n nFigure 2 n nProportion of the world population living in urban areas n n n nThe understanding of how urban environments affect health outcomes and can produce health benefits is therefore an urgent priority, as recognised by WHO in their declaration of 2010 as the Year of Urban Health. From this perspective, there are reasons to be optimistic. The idea of the so-called urban advantage encapsulates the health benefits of living in urban as opposed to rural areas. However, factors such as economic growth and associated urban expansion cannot be relied on to drive improvements in health outcomes. Health improvements need to be actively planned for. The Healthy Cities movement has appreciated this fact and generated much action. Assessments have, however, pointed to a gap between aspirations and outcomes and limitations in the coherence of the models behind action. n nIn response to this problem, the UCL Lancet Commission met from November, 2009, to June, 2011, bringing together an interdisciplinary team of experts to under stand how better health outcomes can be delivered through interventions in the urban environment in cities across the world, and to generate policy recommendations. We began with the definition of health as both the absence of ill health and the presence of mental and physical wellbeing,6 and the urban environment as the physical context within which urban activities take place, including the material fabric of buildings and infrastructure and their spatial organisation. The Commission focused on the potential for shaping the urban environment for better health outcomes; we explicitly did not address the issue of health-service provision within cities, but acknowledge that this is a key component of urban policy. We undertook expert-led reviews of available studies and desk-top research into the connection between urban planning and health in more than a dozen cities, with additional information provided by Commission members who have experience of working in many of these cities. The work informed discussions at monthly meetings with experts in public health, planning, architecture, building physics, engineering, development studies, anthropology, and philosophy. n nThe Commission developed an approach based on complexity thinking—an approach that looks at the interconnected elements of a system and how that system has properties not readily apparent from the properties of the individual elements—and used this approach to develop proposals for an effective way forward. We begin by addressing the arguments around the urban advantage idea and then review the work of the Healthy Cities movement in the promotion of action for urban health. We then set out a complex systems approach for the understanding of how urban environments affect urban health, followed by five short case studies of urban interventions: the inter-related domains of sanitation and water management, building standards and indoor health, transportation and the links to mobility, urban form and the urban heat island effect, and the promotion of urban agriculture. We then turn to the implications of our analysis for urban governance if effective interventions to improve urban health are to be delivered, concluding with recommendations for policy and practice.

The comfort, energy and health implications of London's urban heat island

The urban heat island (UHI) is a well-known effect of urbanisation and is particularly important in world megacities. Overheating in such cities is expected to be exacerbated in the future as a result of further urban growth and climate change. Demonstrating and quantifying the impact of individual design interventions on the UHI is currently difficult using available software tools. The tools developed in the LUCID (‘The Development of a Local Urban Climate Model and its Application to the Intelligent Design of Cities’) research project will enable the related impacts to be better understood, quantified and addressed. This article summarises the relevant literature and reports on the ongoing work of the project. Practical applications: There is a complex relationship between built form, urban processes, local temperature, comfort, energy use and health. The UHI effect is significant and there is a growing recognition of this issue. Developers and planners are seeking advice on design decisions at a variety of scales based on scientifically robust, quantitative methods. The LUCID project has thus developed a series of tools that (1) quantify the effect of urbanisation processes on local environmental conditions, and (2) quantify the impact of such conditions on comfort, energy use and health. The use of such tools is vital, both to inform policy but also to be able to demonstrate compliance with it.

Noise reduction schemes for chaotic time series

Abstract There has recently been a great deal of interest in the development of noise reduction techniques for noisy trajectories from nonlinear dynamical systems. Particular attention has been shown to their development for use in the analysis of chaotic time series. In this paper we consider the problem in an optimisation context. This allows us to categorise some of the commonly used techniques and to compare the performance of different methods from a theoretical standpoint in order to identify some of the pitfalls that can occur with these methods. Finally this formulation enables us to propose a natural composite method that provides flexibility between speed and stability.

The Lancet Countdown on health and climate change: from 25 years of inaction to a global transformation for public health

The Lancet Countdown tracks progress on health and climate change and provides an independent assessment of the health effects of climate change, the implementation of the Paris Agreement, 1 and th ...

The Lancet Countdown: tracking progress on health and climate change

The Lancet Countdown: tracking progress on health and climate change is an international, multidisciplinary research collaboration between academic institutions and practitioners across the world. It follows on from the work of the 2015 Lancet Commission, which concluded that the response to climate change could be the greatest global health opportunity of the 21st century. The Lancet Countdown aims to track the health impacts of climate hazards; health resilience and adaptation; health co-benefits of climate change mitigation; economics and finance; and political and broader engagement. These focus areas form the five thematic working groups of the Lancet Countdown and represent different aspects of the complex association between health and climate change. These thematic groups will provide indicators for a global overview of health and climate change; national case studies highlighting countries leading the way or going against the trend; and engagement with a range of stakeholders. The Lancet Countdown ultimately aims to report annually on a series of indicators across these five working groups. This paper outlines the potential indicators and indicator domains to be tracked by the collaboration, with suggestions on the methodologies and datasets available to achieve this end. The proposed indicator domains require further refinement, and mark the beginning of an ongoing consultation process-from November, 2016 to early 2017-to develop these domains, identify key areas not currently covered, and change indicators where necessary. This collaboration will actively seek to engage with existing monitoring processes, such as the UN Sustainable Development Goals and WHOs climate and health country profiles. The indicators will also evolve over time through ongoing collaboration with experts and a range of stakeholders, and be dependent on the emergence of new evidence and knowledge. During the course of its work, the Lancet Countdown will adopt a collaborative and iterative process, which aims to complement existing initiatives, welcome engagement with new partners, and be open to developing new research projects on health and climate change.

Impact of climate change on the domestic indoor environment and associated health risks in the UK

There is growing evidence that projected climate change has the potential to significantly affect public health. In the UK, much of this impact is likely to arise by amplifying existing risks related to heat exposure, flooding, and chemical and biological contamination in buildings. Identifying the health effects of climate change on the indoor environment, and risks and opportunities related to climate change adaptation and mitigation, can help protect public health. We explored a range of health risks in the domestic indoor environment related to climate change, as well as the potential health benefits and unintended harmful effects of climate change mitigation and adaptation policies in the UK housing sector. We reviewed relevant scientific literature, focusing on housing-related health effects in the UK likely to arise through either direct or indirect mechanisms of climate change or mitigation and adaptation measures in the built environment. We considered the following categories of effect: (i) indoor temperatures, (ii) indoor air quality, (iii) indoor allergens and infections, and (iv) flood damage and water contamination. Climate change may exacerbate health risks and inequalities across these categories and in a variety of ways, if adequate adaptation measures are not taken. Certain changes to the indoor environment can affect indoor air quality or promote the growth and propagation of pathogenic organisms. Measures aimed at reducing greenhouse gas emissions have the potential for ancillary public health benefits including reductions in health burdens related heat and cold, indoor exposure to air pollution derived from outdoor sources, and mould growth. However, increasing airtightness of dwellings in pursuit of energy efficiency could also have negative effects by increasing concentrations of pollutants (such as PM2.5, CO and radon) derived from indoor or ground sources, and biological contamination. These effects can largely be ameliorated by mechanical ventilation with heat recovery (MVHR) and air filtration, where such solution is feasible and when the system is properly installed, operated and maintained. Groups at high risk of these adverse health effects include the elderly (especially those living on their own), individuals with pre-existing illnesses, people living in overcrowded accommodation, and the socioeconomically deprived. A better understanding of how current and emerging building infrastructure design, construction, and materials may affect health in the context of climate change and mitigation and adaptation measures is needed in the UK and other high income countries. Long-term, energy efficient building design interventions, ensuring adequate ventilation, need to be promoted.

Linear recursive filters and nonlinear dynamics

In this paper we investigate the effects of filtering a chaotic time series with a linear IIR filter. Using the Kaplan and Yorke conjecture it has been argued that such filtering can result in an increase in information dimension. Here we show that the filter dynamics induce an extended dynamical system and that this system possesses a globally attracting invariant graph over the base system. Using this framework we obtain sufficient conditions on the filter dynamics that guarantee that the dimension remains unchanged.

Space heating demand and heatwave vulnerability: London domestic stock

A conceptual framework and methodological approach are developed to understand the potential linkage between urban domestic heat demand and the heatwave vulnerability index, using the London building stock as a case study. A geographic information system (GIS)-based systematic approach towards exploring the impact of the urban built form and the heat island phenomenon on domestic space heating needs and heat-related mortality is demonstrated. The physical properties of individual dwellings were inferred from existing GIS databases as a function of given attributes (such as the form and age of the property). Localized annual heating degree-days (HDD) across London were predicted using a site-specific model. Each dwelling was modelled using a modified version of the steady-state annual domestic energy model. The energy consumption profiles generated were subsequently compared with existing top-down regional energy statistics. In addition, local environmental factors such as built density, green coverage ratio, and land surface temperature were extracted from a combination of GIS and satellite image data sources. By mapping these factors across the Greater London Area, their influence on the risk of heat death during the 2006 heatwave was examined. The model could potentially be utilized to inform urban-scale policies relating to the reduction of CO2 emissions and the identification of heat-vulnerable population groups across London. Un cadre conceptuel et une approche méthodologique sont développés afin de comprendre le lien potentiel entre la demande urbaine en chauffage domestique et lindice de vulnérabilité aux vagues de chaleur, en utilisant le parc bâti de Londres comme étude de cas. La démonstration est faite dune approche systématique basée sur des systèmes dinformation géographique (SIG) visant à explorer limpact de la forme bâtie urbaine et du phénomène de lîlot de chaleur sur les besoins en chauffage de lespace domestique et la mortalité liée à la chaleur. Les propriétés physiques des logements individuels ont été déduites des bases de données SIG existantes utilisées comme une fonction dattributs données (tels que la forme et lâge des biens immobiliers). La prévision des degrés-jours de chauffage (DJC) annuels localisés sur Londres sest faite en utilisant un modèle spécifique au site. Chaque logement a été modélisé en utilisant une version modifiée du modèle dénergie domestique annuelle en régime continu. Les profils de consommation dénergie générés ont été comparés ultérieurement aux statistiques énergétiques régionales descendantes existantes. De plus, les facteurs environnementaux locaux tels que la densité du bâti, le coefficient despaces verts et la température superficielle des terres ont été extraits dune combinaison de sources de données provenant de SIG et dimages satellite. En dressant des cartes de ces facteurs sur la Région du Grand Londres, leur influence sur le risque de mortalité par la chaleur pendant la vague de chaleur de 2006 a été examinée. Ce modèle pourrait potentiellement être utilisé pour influencer les politiques à léchelle urbaine qui sont liées à la réduction des émissions de CO2 et à lidentification des groupes de populations vulnérables à la chaleur sur Londres. Mots clés: parc bâti, changement climatique, parc de logements, consommation dénergie, système dinformation géographique (SIG), demande de chaleur, mortalité liée à la chaleur, surchauffe, planification durable, îlot de chaleur urbaine

Health effects of home energy efficiency interventions in England: a modelling study

Objective To assess potential public health impacts of changes to indoor air quality and temperature due to energy efficiency retrofits in English dwellings to meet 2030 carbon reduction targets. Design Health impact modelling study. Setting England. Participants English household population. Intervention Three retrofit scenarios were modelled: (1) fabric and ventilation retrofits installed assuming building regulations are met; (2) as with scenario (1) but with additional ventilation for homes at risk of poor ventilation; (3) as with scenario (1) but with no additional ventilation to illustrate the potential risk of weak regulations and non-compliance. Main outcome Primary outcomes were changes in quality adjusted life years (QALYs) over 50u2005years from cardiorespiratory diseases, lung cancer, asthma and common mental disorders due to changes in indoor air pollutants, including secondhand tobacco smoke, PM2.5 from indoor and outdoor sources, radon, mould, and indoor winter temperatures. Results The modelling study estimates showed that scenario (1) resulted in positive effects on net mortality and morbidity of 2241 (95% credible intervals (CI) 2085 to 2397) QALYs per 10u2005000 persons over 50u2005years follow-up due to improved temperatures and reduced exposure to indoor pollutants, despite an increase in exposure to outdoor-generated particulate matter with a diameter of 2.5 μm or less (PM2.5). Scenario (2) resulted in a negative impact of −728 (95% CI −864 to −592) QALYs per 10u2005000 persons over 50u2005years due to an overall increase in indoor pollutant exposures. Scenario (3) resulted in −539 (95% CI −678 to -399) QALYs per 10u2005000 persons over 50u2005years follow-up due to an increase in indoor exposures despite the targeting of pollutants. Conclusions If properly implemented alongside ventilation, energy efficiency retrofits in housing can improve health by reducing exposure to cold and air pollutants. Maximising the health benefits requires careful understanding of the balance of changes in pollutant exposures, highlighting the importance of ventilation to mitigate the risk of poor indoor air quality.

Urban social housing resilience to excess summer heat

The potential levels of exposure to indoor overheating in an urban environment are assessed for vulnerable social housing residents. Particular focus is given to the synergistic effects between summertime ventilation behaviour, indoor temperature and air pollutant concentration in relation to energy retrofit and climate change. Three different types of social housing are investigated (1900s’ low-rise, 1950s’ mid-rise and 1960s’ high-rise). The case study dwellings are located in Central London and occupied by vulnerable individuals (elderly and/or people suffering from ill-health or mobility impairment). Indoor temperature monitoring suggests that occupants are already exposed to some degree of overheating; the highest levels of overheating occur in 1960s’ high-rise tower blocks. The thermal and airflow performance simulation of a mid-floor flat in the 1960s’ block under the current and projected future climate indicates that improved natural ventilation strategies may reduce overheating risk to a certain extent, with night cooling and shading being slightly more effective than all-day rapid ventilation. However, their potential may be limited in future due to high external temperatures and the undesired ingress of outdoor pollutants. This highlights the need for the development of combined strategies aiming to achieve both indoor thermal comfort and air quality.