Urban heat: an increasing threat to global health

Impact of urban greening on population health in sub-Saharan Africa: a scoping review protocol

INTRODUCTION

The rate of urbanisation in sub-Saharan Africa (SSA) has increased remarkably, with the urban population expected to double by 2050. This rapid urbanisation, industrialisation and climate change pose serious public health challenges resulting from increased heat waves and other environmental changes. Urban greening holds promise as a climate change mitigation and adaptation strategy, leading to biodiversity conservation and enhancing the physical, mental and social well-being of the population.

METHODS AND ANALYSIS

This scoping review aims to identify and synthesise studies that investigated the availability and utilisation of green spaces, the factors that affect the utilisation of green spaces as well as the health impacts of urban greening in SSA. A systematic search will be conducted across multiple databases (MEDLINE, PubMed, JSTOR, SCOPUS and Green FILE) and grey literature sources for papers published up to 2024, in line with established scoping review frameworks. The data will be charted and extracted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, Extension for Scoping Reviews. We will further synthesise and use thematic analysis to fully understand the relationship between urban greening and population health in SSA.

ETHICS AND DISSEMINATION

Ethical approval will not be required because primary data will not be collected for the study. The results of this study come from published articles, which are publicly available. The results of the review will be submitted to a peer-reviewed journal for publication and presented at workshops and conferences.

REGISTRATION

The scoping review protocol has been registered on the Open Science Framework https://osf.io/nfh68.

Is home where the heat is? comparing residence-based with mobility-based measures of heat exposure in San Diego, California

BACKGROUND

Heat can vary spatially within an urban area. Individual-level heat exposure may thus depend on an individual's day-to-day travel patterns (also called mobility patterns or activity space), yet heat exposure is commonly measured based on place of residence.

OBJECTIVE

In this study, we compared measures assessing exposure to two heat indicators using place of residence with those defined considering participants' day-to-day mobility patterns.

METHODS

Participants (n = 599; aged 35-80 years old [mean =59 years]) from San Diego County, California wore a GPS device to measure their day-to-day travel over 14-day intervals between 2014-10-17 and 2017-10-06. We measured exposure to two heat indicators (land-surface temperature [LST] and air temperature) using an approach considering their mobility patterns and an approach considering only their place of residence. We compared participant mean and maximum exposure values from each method for each indicator.

RESULTS

The overall mobility-based mean LST exposure (34.7 °C) was almost equivalent to the corresponding residence-based mean (34.8 °C; mean difference in means = -0.09 °C). Similarly, the mean difference between the overall mobility-based mean air temperature exposure (19.2 °C) and the corresponding residence-based mean (19.2 °C) was negligible (-0.02 °C). Meaningful differences emerged, however, when comparing maximums, particularly for LST. The mean mobility-based maximum LST was 40.3 °C compared with a mean residence-based maximum of 35.8 °C, a difference of 4.51 °C. The difference in maximums was considerably smaller for air temperature (mean = 0.40 °C; SD = 1.41 °C) but nevertheless greater than the corresponding difference in means.

IMPACT

As the climate warms, assessment of heat exposure both at and away from home is important for understanding its health impacts. We compared two approaches to estimate exposure to two heat measures (land surface temperature and air temperature). The first approach only considered exposure at home, and the second considered day-to-day travel. Considering the average exposure estimated by each approach, the results were almost identical. Considering the maximum exposure experienced (specific definition in text), the differences between the two approaches were more considerable, especially for land surface temperature.

Comprehensive evaluation framework for intervention on health effects of ambient temperature

Despite the existence of many interventions to mitigate or adapt to the health effects of climate change, their effectiveness remains unclear. Here, we introduce the Comprehensive Evaluation Framework for Intervention on Health Effects of Ambient Temperature to evaluate study designs and effects of intervention studies. The framework comprises three types of interventions: proactive, indirect, and direct, and four categories of indicators: classification, methods, scope, and effects. We trialed the framework by an evaluation of existing intervention studies. The evaluation revealed that each intervention has its own applicable characteristics in terms of effectiveness, feasibility, and generalizability scores. We expanded the framework's potential by offering a list of intervention recommendations in different scenarios. Future applications are then explored to establish models of the relationship between study designs and intervention effects, facilitating effective interventions to address the health effects of ambient temperature under climate change.

Socio-environmental modifiers of heat-related mortality in eight Swiss cities: A case time series analysis

In the light of growing urbanization and projected temperature increases due to climate change, heat-related mortality in urban areas is a pressing public health concern. Heat exposure and vulnerability to heat may vary within cities depending on structural features and socioeconomic factors. This study examined the effect modification of the temperature-mortality association of three socio-environmental factors in eight Swiss cities and population subgroups (<75 and ≥ 75 years, males, females): urban heat islands (UHI) based on within-city temperature contrasts, residential greenness measured as normalized difference vegetation index (NDVI) and neighborhood socioeconomic position (SEP). We used individual death records from the Swiss National Cohort occurring during the warm season (May to September) in the years 2003-2016. We performed a case time series analysis using conditional quasi-Poisson and distributed lag non-linear models with a lag of 0-3 days. As exposure variables, we used daily maximum temperatures (Tmax) and a binary indicator for warm nights (Tmin ≥20 °C). In total, 53,593 deaths occurred during the study period. Overall across the eight cities, the mortality risk increased by 31% (1.31 relative risk (95% confidence interval: 1.20-1.42)) between 22.5 °C (the minimum mortality temperature) and 35 °C (the 99th percentile) for warm-season Tmax. Stratified analysis suggested that the heat-related risk at 35 °C is 26% (95%CI: -4%, 67%) higher in UHI compared to non-UHI areas. Indications of smaller risk differences were observed between the low vs. high greenness strata (Relative risk difference = 13% (95%CI: -11%; 44%)). Living in low SEP neighborhoods was associated with an increased heat related risk in the non-elderly population (<75 years). Our results indicate that UHI are associated with increased heat-related mortality risk within Swiss cities, and that features beyond greenness are responsible for such spatial risk differences.

China's public health initiatives for climate change adaptation

China's health gains over the past decades face potential reversals if climate change adaptation is not prioritized. China's temperature rise surpasses the global average due to urban heat islands and ecological changes, and demands urgent actions to safeguard public health. Effective adaptation need to consider China's urbanization trends, underlying non-communicable diseases, an aging population, and future pandemic threats. Climate change adaptation initiatives and strategies include urban green space, healthy indoor environments, spatial planning for cities, advance location-specific early warning systems for extreme weather events, and a holistic approach for linking carbon neutrality to health co-benefits. Innovation and technology uptake is a crucial opportunity. China's successful climate adaptation can foster international collaboration regionally and beyond.

Intestinal alkaline phosphatase improves intestinal permeability and alleviates multiple organ dysfunction caused by heatstroke

Objective

Heatstroke (HS) is a severe acute disease related to gastrointestinal barrier dysfunction, systemic inflammation and multiple organ injury. Many of the functions of Intestinal alkaline phosphatase (IAP) have been linked to gut homeostasis, gut barrier function and inflammation. However, the protective effect of IAP on heatstroke is not fully elucidated. This study aims to explore the protective effect of IAP on heatstroke by maintaining intestinal barrier and improving permeability.

Methods

Male C57BL/6 mice were placed in a controlled climate chamber (ambient temperature: 40.0 ± 0.5 °C; humidity: 60 ± 5 %) until the maximum core temperature (Tc, max) reached 42.7 °C (the received criterion of HS). Then heat exposed mice (n = 195) were divided into three groups: 0.2 mL of 0.9 % physiological saline (HS) or vehicle (HS + Vehicle) or 300 IU IAP (HS + IAP) by gavage at 0, 24, and 48 h after onset. Control group mice (Con) (n = 65) were not exposed to heat and were gavaged with 0.9 % physiological saline of the same volume at the same time.

Results

IAP treatment significantly reduced the levels of endotoxin, FD4, and D-lactate in the blood of heatstroke mice, reduced intestinal permeability and maintained the integrity of the intestinal barrier by increasing the expression of tight junction proteins. Meanwhile, IAP treatment alleviated liver and kidney damage caused by heatstroke, reduced serum levels of inflammatory cytokines, and thus improved survival rate of mice after heatstroke.

Conclusion

This study indicates that IAP can improve the intestinal barrier function and intestinal permeability by increasing intestinal tight junctions, reduce systemic inflammation and multiple organ injury and improving the survival rate of heatstroke. Therefore, we consider IAP may be added to enteral nutrition formulas as a potential means for diseases characterized by intestinal permeability disorders, including heatstroke.

Trees, Climate Change, and Health: An Urban Planning, Greening and Implementation Perspective

The In Conversation: Boundary, Spanners, Thinkers and Policy Actors Round Table Series provides a platform for researchers, policy actors, and implementation experts to elevate discussion on emerging issues, present new and upcoming research, and facilitate conversations around impacts and possible solutions. This brief report, on trees, climate change, and health, reflects a conversation between the authors of this paper, along with supporting literature. It explores the potential of green spaces and trees as a viable strategy to address climate change challenges and simultaneously improve population health, well-being, and health equity. In particular, it highlights the public health benefits of trees and green space, the challenges faced in urban areas, and opportunities for the protection, maintenance and regeneration of urban green space.

Impact of native-plants policy scenarios on premature mortality in Denver: A quantitative health impact assessment

BACKGROUND

Cities often use non-native plants such as turf grass to expand green space. Native plants, however, may require less water and maintenance and have co-benefits for local biodiversity, including pollinators. Previous studies estimating mortality averted by adding green space have not considered the provision of native plants as part of the greening policies.

AIM

We aim to estimate premature deaths that would be prevented by the implementation of native-plants policy scenarios in the City of Denver, Colorado, USA.

METHODS

After conducting interviews with local expert stakeholders, we designed four native-plants policy scenarios: (1) greening 30% of all city census-block groups to the greenness level of native plants, (2) adding 200-foot native-plants buffers around riparian areas, (3) constructing large water retention ponds landscaped with native plants, and (4) greening parking lots. We defined the normalized difference vegetation index (NDVI) corresponding to native plants by measuring the NDVI at locations with known native or highly diverse vegetation. Using a quantitative health-impact assessment approach, we estimated premature mortality averted under each scenario, comparing alternative NDVI with the baseline value.

RESULTS

In the most ambitious scenario, we estimated that 88 (95% uncertainty interval (UI): 20, 128) annual premature deaths would be prevented by greening 30% of the area of census block groups with native plants. We estimated that greening 30% of parking-lot surface with native plants would prevent 14 annual deaths (95% UI: 7, 18), adding the native buffers around riparian areas would prevent 13 annual deaths (95% UI: 2, 20), and adding the proposed stormwater retention ponds would prevent no annual deaths (95% UI: 0, 1).

CONCLUSION

Using native plants to increase green spaces has the potential to prevent premature deaths in the City of Denver, but results were sensitive to the definition of native plants and the policy scenario.

Integrated assessment of personal monitor applications for evaluating exposure to urban stressors: A scoping review

Urban stressors pose a health risk, and individual-level assessments provide necessary and fine-grained insight into exposure. An ever-increasing amount of research literature on individual-level exposure to urban stressors using data collected with personal monitors, has called for an integrated assessment approach to identify trends, gaps and needs, and provide recommendations for future research. To this end, a scoping review of the respective literature was performed, as part of the H2020 URBANOME project. Moreover, three specific aims were identified: (i) determine current state of research, (ii) analyse literature according with a waterfall methodological framework and identify gaps and needs, and (iii) provide recommendations for more integrated, inclusive and robust approaches. Knowledge and gaps were extracted based on a systematic approach, e.g., data extraction questionnaires, as well as through the expertise of the researchers performing the review. The findings were assessed through a waterfall methodology of delineating projects into four phases. Studies described in the papers vary in their scope, with most assessing exposure in a single macro domain, though a trend of moving towards multi-domain assessment is evident. Simultaneous measurements of multiple stressors are not common, and papers predominantly assess exposure to air pollution. As urban environments become more diverse, stakeholders from different groups are included in the study designs. Most frequently (per the quadruple helix model), civil society/NGO groups are involved, followed by government and policymakers, while business or private sector stakeholders are less frequently represented. Participants in general function as data collectors and are rarely involved in other phases of the research. While more active involvement is not necessary, more collaborative approaches show higher engagement and motivation of participants to alter their lifestyles based on the research results. The identified trends, gaps and needs can aid future exposure research and provide recommendations on addressing different urban communities and stakeholders.

Spatially-optimized urban greening for reduction of population exposure to land surface temperature extremes

The population experiencing high temperatures in cities is rising due to anthropogenic climate change, settlement expansion, and population growth. Yet, efficient tools to evaluate potential intervention strategies to reduce population exposure to Land Surface Temperature (LST) extremes are still lacking. Here, we implement a spatial regression model based on remote sensing data that is able to assess the population exposure to LST extremes in urban environments across 200 cities based on surface properties like vegetation cover and distance to water bodies. We define exposure as the number of days per year where LST exceeds a given threshold multiplied by the total urban population exposed, in person ⋅ day. Our findings reveal that urban vegetation plays a considerable role in decreasing the exposure of the urban population to LST extremes. We show that targeting high-exposure areas reduces vegetation needed for the same decrease in exposure compared to uniform treatment.

Urbanization and the Future of Population Health

Policy Points Cities, which are where the majority of the world's population lives today, directly and indirectly shape human health and well-being. Urban health research, policy, and practice are increasingly using a systems science approach to address the upstream and downstream drivers of health in cities, which include social and environmental factors, features of the built environment, conditions of living, and health care resources. To guide future scholarship and policy, we propose an urban health agenda for 2050 focused on revitalizing the sanitation movement, integrating data, scaling best practices, adopting the Health in All Policies approach, and addressing intraurban health inequities.

Without Affordable, Accessible, and Adequate Housing, Health Has No Foundation

Policy Points Today's housing disparities are rooted in the increasing commodification of housing that has taken precedence over the need for shelter, a basic human right. With rising housing costs across the country, more residents are finding their monthly income going to rent, mortgage payments, property taxes, and utilities, leaving little for food and medication. Housing is a determinant of health, and with increasing housing disparities, action must be taken to ensure no individual is displaced, communities remain intact, and cities continue to thrive.

Small-scale urban design interventions: A framework for deploying cities as resource for mental health and mental health literacy

With roughly half of the global population living in cities, urban environments become central to public health often perceived as health risk factors. Indeed, mental disorders show higher incidences in urban contexts compared to rural areas. However, shared urban environments also provide a rich potential to act as a resource for mental health and as a platform to increase mental health literacy. Based on the concepts of salutogenesis and restorative environments, we propose a framework for urban design interventions. It outlines (a) an output level, i.e., preventive and discursive potentials of such interventions to act as biopsychosocial resources, and (b) a process level, i.e., mechanisms of inter- and transdisciplinary collaboration of researchers and citizens in the design process. This approach aims at combining evidence-based, salutogenic, psychosocially-supportive design with a focus on mental health. Implementing low-threshold, resource-efficient options in the existing urban context brings this topic to the public space. Implications for the implementation of such interventions for citizens, researchers, and municipality stakeholders are discussed. This illustrates new directions of research for urban person-environment interactions, public health, and beyond.

The influence of heatwave temperatures on fracture patient presentation to hospital

INTRODUCTION

As global warming continues at its current rate, heatwaves are likely to become an increasing phenomenon. At present, knowledge of the influence of heatwave temperatures on fracture patient presentation to hospital remains limited.

METHODS

This was a retrospective descriptive epidemiology study performed through hospital database review, linked to meteorological data. Emergency Department and Fracture Patient Presentation Data was obtained for the adult (16+) South Glasgow population (population count - 525,839) and the adult (16+) population covered by the West of Scotland Major Trauma Centre (population count - 2,218,326) from May 2021 to August 2021. This was combined with maximum temperature data, along with humidity and humidex data. Humidex is a measure which quantifies the temperature experienced by the patient, through a combined score incorporating both maximum temperature and humidity RESULTS: During the study period, there was one temperature heatwave (19th to 25th July), and four humidex heatwaves (27^th June to 3rd July, 15th to 17th July, 19th to 27th July, 22nd to 26th August). During the temperature heatwave, there was a significantly higher incidence of orthopaedic polytrauma patient presentation (IRR 2.37: p < 0.027), as well as ED patient presentation (IRR 1.07: p < 0.036). The humidex heatwaves were associated with a significantly higher incidence of orthopaedic polytrauma patient presentation (IRR 2.31: p < 0.002) and overall fracture patient presentation (IRR 1.18: p < 0.002). Positive correlations were found between orthopaedic polytrauma patient presentation vs temperature (R=0.217: p < 0.016), ED patient presentation vs temperature (R=0.427: p < 0.001), fracture patient presentation vs temperature (R=0.394: p < 0.001), and distal radius fracture patient presentation vs temperature (R=0.246: p < 0.006).

CONCLUSION

This study finds that heatwave temperatures result in a significantly increased number of orthopaedic polytrauma patients presenting to a Major Trauma Centre. Given the significant resources these patients require for care, Major Trauma Centres should be aware of such findings, and consider staff and resources profiles in response.

Vulnerable, Resilient, or Both? A Qualitative Study of Adaptation Resources and Behaviors to Heat Waves and Health Outcomes of Low-Income Residents of Urban Heat Islands

Little is known of how low-income residents of urban heat islands engage their knowledge, attitudes, behaviors, and resources to mitigate the health impacts of heat waves. In this qualitative study, we conducted semi-structured interviews with 40 adults in two such neighborhoods in Los Angeles California to explore their adaptation resources and behaviors, the impacts of heat waves on physical and mental health, and threat assessments of future heat waves. Eighty percent of participants received advanced warning of heat waves from television news and social media. The most common resource was air conditioning (AC) units or fans. However, one-third of participants lacked AC, and many of those with AC engaged in limited use due primarily to the high cost of electricity. Adaptation behaviors include staying hydrated, remaining indoors or going to cooler locations, reducing energy usage, and consuming certain foods and drinks. Most of the participants reported some physical or mental health problem or symptom during heat waves, suggesting vulnerability to heat waves. Almost all participants asserted that heat waves were likely to increase in frequency and intensity with adverse health effects for vulnerable populations. Despite limited resources, low-income residents of urban heat islands utilize a wide range of behaviors to minimize the severity of health impacts, suggesting they are both vulnerable and resilient to heat waves.

Urban Air Pollution, Urban Heat Island and Human Health: A Review of the Literature

Many cities of the world suffer from air pollution because of poor planning and design and heavy traffic in rapidly expanding urban environments. These conditions are exacerbated due to the Urban Heat Island (UHI) effect. While there have been studies linking the built environment and air pollution with health, they have ignored the aggravating role of UHI. The past urban planning literature in this field has also ignored the science of materials, vehicles and air pollution, and technological solutions for reducing cumulative health impacts of air pollution and UHI. Air Pollution, built environment and human health are complex discussion factors that involve several different fields. The built environment is linked with human health through opportunities of physical activity and air quality. Recent planning literature focuses on creating compact and walkable urban areas dotted with green infrastructure to promote physical activity and to reduce vehicle emission-related air pollution. Reduced car use leading to reduced air pollution and UHI is implied in the literature. The literature from technology fields speaks to the issue of air pollution directly. Zero emission cars, green infrastructure and building materials that absorb air pollutants and reduce UHI fall within this category. This paper identifies main themes in the two streams of urban air pollution and UHI that impact human health and presents a systematic review of the academic papers, policy documents, reports and features in print media published in the last 10–20 years.

The Changing Climate and Pregnancy Health

PURPOSE OF REVIEW

Climate change is the biggest public health threat of the twenty-first century but its impact on the perinatal period has only recently received attention. This review summarizes recent literature regarding the impacts of climate change and related environmental disasters on pregnancy health and provides recommendations to inform future adaptation and mitigation efforts.

RECENT FINDINGS

Accumulating evidence suggests that the changing climate affects pregnancy health directly via discrete environmental disasters (i.e., wildfire, extreme heat, hurricane, flood, and drought), and indirectly through changes in the natural and social environment. Although studies vary greatly in design, analytic methods, and assessment strategies, they generally converge to suggest that climate-related disasters are associated with increased risk of gestational complication, pregnancy loss, restricted fetal growth, low birthweight, preterm birth, and selected delivery/newborn complications. Window(s) of exposure with the highest sensitivity are not clear, but both acute and chronic exposures appear important. Furthermore, socioeconomically disadvantaged populations may be more vulnerable. Policy, clinical, and research strategies for adaptation and mitigation should be continued, strengthened, and expanded with cross-disciplinary efforts. Top priorities should include (a) reinforcing and expanding policies to further reduce emission, (b) increasing awareness and education resources for healthcare providers and the public, (c) facilitating access to quality population-based data in low-resource areas, and (d) research efforts to better understand mechanisms of effects, identify susceptible populations and windows of exposure, explore interactive impacts of multiple exposures, and develop novel methods to better quantify pregnancy health impacts.

Individually experienced heat stress among elderly residents of an urban slum and rural village in India

The elderly are one of the most vulnerable groups to heat-related illnesses and mortality. In tropical countries like India, where heat waves have increased in frequency and severity, few studies have focused on the level of stress experienced by the elderly. The study presented here included 130 elderly residents of Kolkata slums and 180 elderly residents of rural villages about 75 km south of Kolkata. It used miniature monitoring devices to continuously measure temperature, humidity, and heat index experienced during everyday activities over 24-h study periods, during hot summer months. In the Kolkata slum, construction materials and the urban heat island effect combined to create hotter indoor than outdoor conditions throughout the day, and particularly at night. As a result, elderly slum residents were 4.3 times more likely to experience dangerous heat index levels (≥ 45°C) compared to rural village elderly. In both locations, the median 24-h heat indexes of active elderly were up to 2°C higher than inactive/sedentary elderly (F = 25.479, p < 0.001). Among Kolkata slums residents, there were no significant gender differences in heat exposure during the day or night, but in the rural village, elderly women were 4 times more likely to experience dangerous heat index levels during the hottest times of the day compared to elderly men. Given the decline in thermoregulatory capacity associated with aging and the increasing severity of extreme summer heat in India, these results forecast a growing public health challenge that will require both scientific and government attention.