HOPE E-COURSE STUDENTS -ENGLISH FINAL

Goal: student explains the urban determinants of heat exposure and risk 

 Welcome to the first week of this module. In this week you are going to study the urban determinants of heat exposure and risk. More specifically you will learn about the phenomenon of urban health islands. It is recommended that you read the article of Tong et al (https://doi.org/10.1136/bmj.n2467). Also, chapter 8 of the WHO report on Heat and health in the WHO European Region (2021), is very helpful in understanding the issue of urban determinants of heat exposure and risk (https://www.who.int/europe/publications/i/item/9789289055406). In figure 5.1 you can see that the temperature in the city centre is about 3 degrees Celcius higher than in the surrounding areas. How is that possible?  

Figure 5.1: temperature in the urban area 

Source: Tong et al in BMJ 2021;375 

 The urban structure can aggravate heat risks, especially during the night. This phenomenon is called the Urban Heat Island (UHI) effect. It can result in night-time air temperatures in large cities that are 3-12 C higher than in surrounding rural areas.  

In general, the reasons that it is more hot in cities than in surrounding rural areas are: 

• the absorption and slow release of heat from buildings and other heat-retaining surfaces (f.i. the use of dark-coloured paving or asphalt); 

• residual heat from energy use (f.i. by transport, air conditioners and industrial facilities); 

• a lack of vegetation. Vegetation has a cooling effect.   

The first source that influences the heat in cities are the buildings and paved streets. In cities, there may be a high density of buildings. Depending on the material that is used, heat is absorbed and released from these buildings. The same goes for paving or asphalt. The architecture and the height of buildings or building blocks may also influence the way the natural air flow moves through the streets.  A second source is the so-called anthropogenic heat emissions. This refers to the heat released into the atmosphere as a result of human activities. Examples are heat released by industry, by (public) transportation (cars, large vehicles) air conditioning used to heat or cool buildings. The last source of heat is the amount of or the lack of vegetation, green areas and water areas. The city architecture where green and buildings are nicely integrated has a positive effect on heat reduction. Unlike (parts of) cities where this is not the case. All sources are also influenced by the climate zone in which the city is located (f.e. wet, dry, (sub)tropical) in combination with the (rural) vegetation.  

Within a city, the extremely hot temperatures manifested during a heat wave are not evenly distributed over the city. Temperatures are significantly higher in parts of cities with high population density, poor housing conditions, less green space and/or more asphalt.  Consequently, not all residents of a city are exposed to the same heat stress. In module 2 we learned that some residents are more susceptible to heat stress than others. These are the elderly, people with chronic health conditions and other vulnerable population groups (f.e. those who live in areas with a poor economic situation). So, when they live in a so-called UHI the chance that they suffer from heat stress gets even larger than when they would live in another part of the city.   

In the Summer of 2023, the following article was published in the New York Times New Heat Wave Descends on Europe, as It Struggles to Adapt - The New York Times (nytimes.com)  

Source: Francesca Volpi for The New York Times, July 14, 2023 

 The biggest win in tackling heat-related health problems comes from investments in the living environment.  The article shows that in Europe the heat strategies of governments are somewhat lacking behind those of the United States. Cultural elements of cities may prohibit certain interventions from implementation. Long-term planning aimed at heat reduction is lacking and so are targeted investments. From the WHO report (https://www.who.int/europe/publications/i/item/9789289055406) we also know that there is not enough urban temperature data to target specific areas in the urban setting.  Last but not least, those who are responsible for health-related issues are most of the time not able to influence urban planning or the construction of buildings. These types of Interventions are also expensive and take time and investments without too many additional benefits for those who pay (like private investors). 

Knowledge Check:  

(please Insert H5P module 5 5.1 )