A bus terminal with no greenery and shade highlights the Urban Heat Island Effect in Ilidža, Bosnia and Herzegovina, and its impact on residents’ health, as explored in a study by CENER 21 featuring insights from Ema Midžić.
According to latest data, the year 2024 is very likely to surpass 2023 as the warmest on record. The annually rising temperatures prompted UN Secretary General António Guterres in July 2024 to issue a “Call to Action on Extreme Heat”, discussing the wide-ranging global impacts extreme heat events have on societies and the environment, and emphasizing the need for rapid action to limit global temperature rise.
The impacts of extreme heat on humans, infrastructure, and ecosystems are diverse and severe. They range from serious health hazards, decreased workers’ productivity and overall economic activity to the destruction of infrastructure – particularly in the transport, energy, water and communication sector. They also bring about significant strains on the healthcare sector and exacerbate environmental degradation such as water scarcity, droughts and reduced plant and crop growth, resulting in decreased harvest yield and therefore food insecurity.
One possible mitigation strategy to extreme heat in cities involves passive cooling measures. This can include urban greening, the installation of green roofs, green walls and light-colored or reflective streets, sidewalks and parking lots, as well as the installation of shading structures. These passive cooling measures are meant to mitigate the so-called urban heat island (UHI) effect.
An UHI describes an area in an urban setting that is significantly warmer than the rural surroundings. The increased heating up of cities is related to several factors: heat getting trapped and stored due to high and side by side buildings, building materials, street surfaces and canyons, traffic, space heating, industries, air pollution, and a reduction of wind speed. The extent of the temperature difference varies and depends on meteorological, locational and urban characteristics. But cloud cover, precipitation, solar irradiation, air temperature and wind speed can vary significantly between an urban setting and its immediate rural surrounding. According to latest numbers, cities globally are heating up twice the average due to increased urbanisation and UHI effect.
In his “Call to Action on Extreme Heat”, the UN-Secretary General described extreme heat as the “silent killer” alluding to the dangerous health risks and high number of deaths associated with extreme heat. Extreme heat is killing “silently” because, on the one hand, little awareness is being raised of the actual dangers of heatwaves and their potential life-threatening impact. On the other hand, extreme heat is also killing in silence because of the difficulty of actually collecting detailed data on the correlation between extreme heat and health.
Still, we know that extreme heat affects human health in multiple and severe ways. On a direct level, the human body often cannot compensate for the heat it is exposed to, experiencing heat stress. If the body temperature rises above 38C, a person can experience heat exhaustion, heat cramps and/or hyperthermia. Heat stress can increase demand on the cardiovascular system and promote dehydration, blood clots, and electrolyte imbalances. When the body temperature rises above 40.5C, a heatstroke can occur, potentially leading to organ damage, loss of consciousness and risk of death, requiring immediate emergency treatment. Hot and especially humid conditions can also lead to heat rash, occurring when sweat is trapped in the skin.
The study revealed a consistent and increasing temperature difference between urban and rural areas of Ilidža, with urban areas consistently experiencing higher temperatures.
On a more indirect and long-term level, climate-induced heatwaves are often associated with poor air quality due to lack of wind and precipitation, which trap pollutants in the air. This exacerbates respiratory distress, but also inflammatory skin conditions such as eczema and rosacea. Additionally, extreme weather conditions influenced by climate change, such as severe heat, increase the risk of vector-borne diseases across expanding geographical ranges. Vector-borne diseases such as dengue fever and malaria are bacterial or viral diseases transmitted to humans and other animals by vectors like mosquitos, ticks, and fleas.
While the physical consequences of extreme heat on the human body are well documented and known, only recently mental health and its correlation to extreme heat has caught public health professionals’ interest. According to research published in 2023, depression and anxiety can increase during extreme heat, and psychotic outbreaks are more likely to occur. The persisting exposure to extreme heat also affects cognitive abilities like memory, concentration, and intellectual ability.
Extreme heat does not affect everyone equally. Different vulnerable groups within society suffer more from extreme heat and its related health risks. These include elderly people, infants and toddlers, people with chronic medical conditions, homeless people, economically vulnerable people, outdoor workers, and persons under the influence of alcohol and drugs.
The effect of urban heat islands on the health of the residents of Ilidža
To highlight the connection between the UHI effect and the health conditions of the residents of Ilidža, in Bosnia and Herzegovina, the “Center for Energy, Environment and Resources” (CENER 21) conducted a comprehensive long-term study analyising these linkages and recommending adaptation pathways. The study analyzed heat- and health-related data from 2021, 2022, and 2023.
CENER 21, an AMWAJ member, is a non-government organization based in Sarajevo dedicated to developing and implementing projects focused on sustainable development in Bosnia and Herzegovina and Southeast Europe. In 2023, CENER 21 started the research on the UHI effect in Ilidža, a small town located near Sarajevo, the capital of Bosnia and Herzegovina. Ilidža can be considered a suburb of Sarajevo, but it has its own municipality and a population of approximately 65,000 inhabitants. When asked why Ilidža was chosen for this study, Ema Midžić, project associate at CENER 21 and the project manager responsible for the UHI project, explained:
“Ilidža is located very close to central Sarajevo and has a city center with a bus terminal. This bus terminal is completely open, with no shade at all and is frequently crowded with people waiting for the bus to commute to work or home. Through discussions with local residents, we determined that this terminal would be the best representation of the UHI effect. Its central location combined with the surrounding rural areas are the same altitude, makes it easier to measure and compare temperatures between urban and rural zones, directly linking them to the UHI effect.”
In addition to geographical consideration, CENER 21 chose to study the UHI effect and its impact on the health of Ilidža’s residents because no similar research has been conducted in Bosnia and Herzegovina. This is largely due to a lack of data on temperature and its correlation with health risks.
“In Bosnia and Herzegovina, some research has identified the presence of UHI is in the centre of Sarajevo”, Midžić said. “Although I could not locate the original study, there is a study included in the climate action plan for Sarajevo. It confirmed the existence of the UHI effect in the city, but that was it – no further research was conducted due to the lack of temperature data. This gap inspired us to undertake our study. Our objective was to produce a document that not only confirmed the UHI effect but also highlighted its impact on health. With this evidence, we aim to use the document as a foundation for future projects. Until now, we lacked a baseline, from which we can start further research.”
Analyzing the data and its correlation to health
The research conducted by CENER 21 incorporated both quantitative and qualitative components. For the quantitative aspect, temperature and humidity levels were measured and compared between rural and urban sites in Ilidža over three consecutive three years in order to identify long-term trends.
The qualitative component of the research involved structured interviews with Ilidža residents. These interviews captured personal experiences and perceptions related to living in the urban heat island, with a particular focus on health issues.
The study revealed a consistent and increasing temperature difference between urban and rural areas of Ilidža, with urban areas consistently experiencing higher temperatures. To examine the correlation between higher temperatures and health issues, CENER 21 collaborated with the J.U. Ilidža Health Center. For 2021 and 2022, the collaboration involved analyzing recorded health data, while for 2023, it included active data collection by healthcare providers. This enabled the establishment of a direct correlation between heat exposure and reported health problems.
The study specifically focused on respiratory and cardiovascular health issues, skin diseases and mental health issues. The analysis of the research highlighted a seasonal variation in the occurrence of health issues. Across all three years, respiratory and cardiovascular diseases were most prevalent during the colder months, attributed to the start of the heating season and increased pollution. However, conditions such as dehydration and heat exhaustion but also respiratory diseases surged during the summer months as temperatures rose.
In 2023, the year with the highest recorded temperatures and with the most pronounced UHI effect, there was a noticeable general increase in the incidence of diseases, particularly respiratory conditions. The peak of health problems – including exhaustion, dehydration, heat cramps, and rashes – was recorded in June and August 2023. The data also revealed a significant rise in health issues among two age groups: those under 20 and those under 70 years old. Mental health issues showed a particularly striking increase among young people.
Additionally, the 2023 data underscored the differing responses of urban and rural environments to temperature changes. “Our data analysis from June to November shed light on how urban and rural environments respond differently to temperature changes,” Midžić elaborated. “In urban areas, there was a consistently higher correlation between temperature changes and disease incidents throughout most of the year, indicating that health outcomes are more directly influenced by temperature.
“When we looked at monthly trends, June and October showed a moderate positive correlation between temperature and diseases in both rural and urban areas. However, during the peak summer months of July and August, there was no significant correlation in rural areas whereas urban areas maintained a strong correlation. This clearly highlights the urban heat effect.”
The interviews conducted as part of the research included questions about awareness of UHI effect and its health impacts, personal experiences with symptoms or health problems related to UHI, and strategies for protection against its negative effects. Additionally, the role of local authorities in mitigating UHI and the condition of green areas in the urban areas were explored.
The majority of respondents expressed discomfort in urban areas where they felt more exposed to extreme heat compared to the rural surroundings. Women, in particular, cope with this discomfort by avoiding the urban area of Ilidža altogether. When asked about health issues, most people reported breathing difficulties, as well as increased exhaustion and fatigue, in the urban environment.
Although the analysis of the interview shows a strong awareness among residents of Ilidža about the impacts of UHI effect on health and well-being, a high percentage of respondents are still unfamiliar with methods of protection against these negative impacts.
Recommendations and next steps
“I hope that the insights from this study will inform and shape public health policies,” said Midžić, summarizing her aspirations for the study’s impact. “Here in Ilidža, we face many issues with illegal construction, which has led to the disruption of natural wind corridors. I hope this study can help us advocate for change and improve the situation.”
The study concludes with 10 recommendations to mitigate the UHI effect, including increasing urban greening and creating more urban gardens, installing green or cool roofs and cool sidewalks, and developing sustainable urban planning that incorporates heat-resistant buildings and water distribution points across the city. Additionally, it suggests creating specialized programs to support those most affected by extreme heat, such as the elderly, children, and other vulnerable groups.
