Heat islands increase mortality rates in European cities
Published: Tuesday, Jan 23rd 2024, 11:40
Updated At: Tuesday, Jan 23rd 2024, 11:40
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Heat islands in European cities increase the mortality rate on extremely hot days by 45 percent. On extremely cold days, however, heat islands reduce mortality by an average of seven percent, as a study from Lausanne shows.
"Our study shows that heat islands are not a comfort problem, but cause considerable health costs, for example through higher respiratory and cardiovascular risks that reduce life expectancy," study leader Gabriele Manoli was quoted as saying in a press release issued by the Swiss Federal Institute of Technology Lausanne (EPFL) on Tuesday.
The heat island effect means that cities heat up more than rural areas. This is triggered by a number of different characteristics of cities: Sealed soils, poor air circulation due to buildings, a lack of vegetation, and additional heat generated by traffic, industry and heating systems.
Damage in summer, protection in winter
EPFL researcher Manoli, together with researchers from London and Singapore, analyzed heat islands in 85 cities in Europe between 2015 and 2017. The cities studied included Geneva, Zurich and Basel.
The results were published in the journal "Nature Communications". They compiled data and simulations to assess both the damage caused by heat islands in summer and the protection they provide during cold snaps in winter.
On the hottest days in the years studied, these urban heatwaves caused an average of one additional death per 400,000 inhabitants, as the analysis showed. This contrasts with a reduction of one death per two million inhabitants per day on extremely cold days.
However, the differences between the various cities were large. While the negative effect of summer heat islands was greater in cities in hotter regions such as Spain, the positive effect of heat islands in winter was greater in colder regions such as Finland. In Geneva, according to the EPFL, urban heat islands caused four additional heat-related deaths per 100,000 inhabitants each year, but prevented 3.4 cold-related deaths.
Costs of heat waves
The researchers put the cost of urban heat islands at an average of 192 euros per year, the equivalent of around 180 francs per city dweller. According to the EPFL, this is comparable to the cost of air pollution or the price paid by city dwellers for public transport.
According to the study, the net cost of heat islands in Geneva is 20.7 euros (just under 20 francs) per adult inhabitant per year. Heatwaves in summer cause costs of 155 euros, while the reduced cold in winter saves 134 euros.
In Trieste, Italy, the net costs amounted to 184.4 euros. According to the study, the heat island effect even saves money in Helsinki, Finland: 113.9 euros are saved per inhabitant.
"Our study shows that the effects of heat islands vary greatly from city to city and from season to season. In future, political decision-makers will be able to base their decisions on this specific information," said Manoli.
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