Transforming Cities to Preserve the Health of Present and Future Generations

* This article was originally published by Santé publique France in La Santé en Action on December 15, 2022. Read the full issue dedicated to urban planning and health.

* One of the co-authors, Mathilde Pascale, is a Santé publique France representative in the IANPHI Committee on Climate Change and Health.

© City of Grenoble

At the end of 2021, on the sidelines of COP26, an international alliance of non-governmental organizations representing healthcare professionals from all over the world prescribed climate action as “a remedy for patients” [1]. A symbolic way of emphasizing that climate change is already claiming victims everywhere in the world, and that policies aimed at reducing greenhouse gas emissions and building adaptive capacities are essential to preserve health in all its dimensions, including mental health. The opinion of caregivers is consistent with that of researchers [2; 3] and public health agencies: climate action is public health action [4].

Unprecedented challenges

All of these communities agree on the need to act quickly, in a concerted and interdisciplinary manner. The unprecedented environmental, health and social challenges we face can no longer be addressed separately or on an ad hoc basis. The interdependence between the environment and health is now widely recognized, especially through the concepts of Planetary Health¹ [5] and One Health² [6]. The implementation of integrated preservation actions is essential [7]. According to the Intergovernmental Panel on Climate Change (IPCC), climate change mitigation, adaptation, nature conservation and the reduction of inequalities are essential for a “viable future” [7].

In terms of environmental challenges, climate change associated with the destruction of biodiversity and the alteration (in quality and quantity) of natural resources constitute a unique situation in human history. The planetary boundary theory was developed to help grasp the extent of environmental issues: it assesses the state of nine natural processes considered essential to the stability of the biosphere [8]. Five of these nine³ processes are already in a state of imbalance that threatens the terrestrial ecosystem: climate change; loss of biodiversity; changes in land use; disruption of global phosphorus and nitrogen bio-geochemical cycles⁴; chemical pollution [9]. Thus, it is insufficient to act solely on the climate, for example by investing in future technological solutions for trapping greenhouse gases. Societies need systemic transformation to redress these five imbalances that are already having massive impacts. Outdoor air pollution alone is responsible for 4.2 million premature deaths per year worldwide [10], including 40,000 deaths in mainland France [11].

We do not yet have indicators to globally quantify the effects of other planetary imbalances on health, but the IPCC already points to the dramatic impacts of climate change and its repercussions on natural and human ecosystems [7], via extreme climatic events, deterioration in the quantity and quality of food and water resources, mental health, certain infectious pathologies, or even migration. The World Health Organization (WHO) estimates that the health impacts are set to cost US$2–4-billion per year by 2030. This is a minimum estimate that only takes into account a small number of impacts [12].

Faced with this sombre observation, hope comes from the fact that it is possible to transform lifestyles and environments to simultaneously meet environmental, health and social challenges [5; 13]. This means mobilising new, creative and experimental approaches to tackle complex problems and help accelerate change, especially at city level [14].

Acting on the urban environment to protect the health of humans and ecosystems

Urban territories are among the places targeted for action to carry out these transformations. In 2018, approximately 55% of the world’s population lived in urban areas, a proportion that is expected to increase to 68% by 2050 [15]. These territories are also where the majority of economic wealth is concentrated [16]. Considered as complex socio-ecological systems, urban territories must be apprehended by adopting systemic approaches. However, the use of this type of approach and the importance of the repercussions in terms of health are still insufficiently considered by decision-makers [17].

Photo credit: J. Falguière 

Urban territories are now very sensitive to environmental issues

Climate change increases the risk of complex crises via extreme events that lead to massive disorganization within urban systems [7]. These events can have lasting impacts on mortality, health care utilization or mental health.

In these territories, populations are overexposed to major health risks. Four out of the nine⁵ main environmental determinants of health [18] are omnipresent in urban areas: air pollution; temperature; noise; urban characteristics (urban fabric, built environment, land use, chemical pollution, etc.). However, these exposures are directly linked to the city’s organizational choices, particularly in terms of development, urban sprawl and transport, which also contribute to climate change. By acting on these choices, it is therefore possible to work both in favour of the environment and health, and to protect the health of current and future populations. This is, for example, the case of interventions aimed at reducing motorized mobility in favour of active mobility (i.e. non-motorized mobility, such as walking or cycling), which helps to reduce greenhouse gas emissions, while generating very significant health benefits [19] via increasing physical activity and reducing exposure to noise and air pollutants from road traffic.

To illustrate the importance of overexposure in urban areas, and therefore the potential co-benefits of interventions, we can note the considerable impact of environmental pollution generated by motorized mobility, which is the main form of transport today. Chronic exposure to ambient air pollutants is associated with the development of many diseases such as respiratory, cardiovascular and neurodegenerative diseases, perinatal health problems, and cancers. Air pollution is the first environmental determinant of health, with a considerable impact on quality of life, life expectancy and the health system. In France, almost three-quarters of deaths due to air pollution occur in urban communities (> 2,000 inhabitants) [20]. Noise, particularly related to traffic, is associated with one of the highest environmental disease burdens in Europe, after air pollution [21], mainly via the consequences of the discomfort caused, sleep disturbances and ischemic heart disease. It is also associated with learning disabilities in children.

Another example is how the lack of nature in the city aggravates exposure to heat. The latter is associated with the deterioration of many conditions such as mental health, cardiovascular, respiratory and renal diseases, and pre- or post-natal pregnancy-related pathologies affecting both mother and infant. The risk is exacerbated by the effects of urban heat islands (UHI) [22]. Heat waves are the deadliest extreme weather event in France today, totalling more than 39,500 deaths since 1974⁶. The IPCC considers heat as one of the most important structural risks that Europe will face in the coming years [7].

In addition to their cooling effect on cities, green spaces are associated with an improvement in the overall state of health, mental health and even the behavioural development of children [23]. They also lead to a decrease in all-cause mortality [24; 25]. Be analysing different conceptual frameworks that illustrate how urban green spaces can contribute to health [26; 30], it is possible to assess the health potential of green spaces according to four main functions (see figure below). Although all of the mechanisms that could explain these benefits have not yet been fully elucidated, the conceptual frameworks proposed and the results of epidemiological studies are sufficiently robust to consider that lack of green space is one of the factors influencing mortality [31]. Urban green spaces thus represent major potential as a community intervention that simultaneously addresses public health issues (in particular the reduction of chronic diseases and their associated symptoms) and challenges linked to serious environmental changes, i.e. the fight against the effects of climate change and the protection of water resources and biodiversity [32; 33]. Thus, their implementation at all levels of urban land development has been strongly encouraged in recent years, as proved by the growing availability of documents supporting such action [34; 35]. 

Finally, there is a notable scarcity of scientific studies focusing on the health effects of biodiversity within cities (diversity of living species, wild fauna and flora). Also, the majority of existing studies analyse the risks (e.g. allergenics, stinging species, risks of zoonoses) and not the benefits. Some studies, however, point to co-benefits for mental health through actions that protect wildlife in the city [36]. Yet the deterioration of mental health is also one of the major impacts highlighted by the IPCC [7], as associated with extreme events but also with increasing anxiety about current environmental changes.

Figure. Effects of Green Spaces on Health [37]

Outlook

There is no turnkey solution to the current challenges, but there are many opportunities for action favourable to health, climate and biodiversity.

For researchers, it is a matter of supporting these developments via the dissemination of knowledge; through the co-production of tools adapted to the evaluation of these interdependent issues and decision-making; by the construction of productive interactions between scientists, decision-makers and society. The objective must be to better consider knowledge, as applied to a specific context, for decision-making [38]. These activities, called “boundary spanning”, go far beyond a simple process of disseminating science (via communication, applied science and advocacy).

For elected officials and municipal engineering services, as for other stakeholders in regional planning, priority should be given to setting up decision-making organizations and processes that tackle climate change adaptation and mitigation issues, protection of biodiversity and public health in a concerted manner. They must propose creative and evidence-based solutions that are adapted to the local context. This is all the more important since, in terms of healthy urban planning, adaptation and mitigation of climate change, and preservation of biodiversity, the several regulatory tools that exist too often operate in a disconnected way. The concept of health within all WHO policies aims to promote and facilitate inclusive and collaborative approaches [39] (see article “Urban health challenges: WHO findings and proposals” in the full issue of La Santé en Action).

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1. Planetary Health integrates the health of human civilizations and the ecosystems on which it depends, in a cross-disciplinary approach.
2. One Health is an integrated and unifying approach that aims to sustainably balance and optimize the health of people, animals and ecosystems.
3. Other processes studied are ocean acidification, stratospheric ozone depletion, global freshwater use and aerosol loading.
4. Transport and transformation of a chemical element between the atmosphere, the hydrosphere, the geosphere and the biosphere.
5. The five other environmental determinants of health proposed by Rojas-Rueda et al. (2021) are environmental tobacco smoke, radon, heavy metals, radiation and chemical pollutants.
6. Departmental data available on Géodes.santepubliquefrance.fr, Health determinants/Climate/Heat wave section

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For more information

Seminar dedicated to climate change and public health. Organized by Santé Publique France and the International Association of National Public Health Institutes.

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