TRUE OR FAKE. Is Paris the European city with the highest excess mortality during heat waves?

Almost twenty years ago, in the heart of August 2003, an intense heat wave hit France. According to data from Public Health France, nearly 15,000 people have died “in excess” during this period, i.e. about 60% more than expected. As this sinister date approaches, a worrying observation has been relayed by many Internet users on social networks: Paris is the European city where the risk of excess mortality (abnormally high mortality rate) is the greatest, in case of very hot weather.

According to Geo magazine, “France is home to the deadliest city in Europe in the event of a heat wave”. A formulation taken from the analysis of a British study published in March 2023 in the scientific journal The Lancet Planetary Earth. The co-founder of Mediapart Edwy Plenel or the elected ecologist of the 18th arrondissement of Paris Emile Meunier were alarmed in various tweets.

So what does this study really say? And can we conclude that the French capital ranks at the top of European cities with the highest risk of excess mortality in the event of a heat wave?

Several Italian cities in front of Paris

The researchers studied the excess mortality linked to heat and cold in 854 cities in 30 countries (the 27 countries of the EU, to which they added Norway, Switzerland and the United Kingdom and subtracted the cities overseas). sea). These urban areas have more than 50,000 inhabitants and concentrate 40% of the population. The study authors also made sure that each city’s demographics (age categories) did not skew the results. In other words, if we observe high excess mortality in a given city, it is not because it has more elderly people, a more vulnerable population.

Is Paris at the top of the charts? Franceinfo interviewed Pierre Masselot, co-author of the study and researcher at the Environment and Health Modeling Laboratory at the London School of Health and Tropical Medicine. “Paris is the city with the highest risk [de surmortalité] for the heathe admits, but based on the capitals of all the countries we studied”. Thus, the alarmist presentation made by certain media “is not quite true”according to the statistician.

On the other hand, Paris can be presented as the European capital with the highest risk of excess mortality in the event of a heat wave. According to the graph above, it appears in the lead ahead of other capitals such as Amsterdam, Rome or Zagreb. “If we look at the full sample of 854 cities, there are a few that have a higher risk than Paris [en cas de chaleur extrême]“, shade Pierre Masselot. The Italian cities of Bologna and Milan come first and second respectively, Salamanca (Spain) and Capri (Italy) come third and fourth. Of all the cities studied, and not just the capitals, Paris ranks fifth.

Eastern Europe very vulnerable

Still, for the time being, Europeans are dying more “in excess” because of the cold than the heat. This is one of the main conclusions of the study, with an excess mortality of 200,000 cold-related deaths, while there are ten times fewer (20,100 deaths) related to heat over the period 2000-2019. Thus London is the capital where the risk of excess mortality is the greatest in the event of a cold snap. However, Eastern Europe (Poland, Czech Republic, Slovakia, Hungary, Romania, Bulgaria) appears to be the most vulnerable geographical area, whether to cold or heat. This phenomenon is widely observed on the following maps.

By publishing their study on the excess mortality linked to extreme temperatures in European cities, the authors precisely wished to provide “valuable information for policy makers to design national, regional and local climate and public health policies”. Pierre Masselot pleads for taking into account the effects of climate change in the design of cities. “To reduce vulnerability to heat, you need less bitumen, and more greenery!”he advocates.

90% of the Parisian population exposed to an urban heat island

The fact that Paris is at the top of the European rankings during heat waves is not insignificant. High temperatures particularly affect urban areas, in particular because of the urban heat island phenomenon (UHI), which distinguishes the temperature in the city, which is warmer, and that in the surrounding countryside, which is cooler. Town planning is directly involved: buildings blocking air circulation, building materials that store heat, car traffic, lack of green spaces and water points…

In Paris, 90% of the population was exposed to a high intensity ICU (between 3 and 6°C difference) and 10% to a very high intensity ICU (more than 6°C difference) in 2021, found franceinfo by analyzing data from the MApUCE project and INSEE. “There is a much larger urban continuum than for other cities [françaises] and also an urban roughness [la hauteur des bâtiments] very important” disrupting air circulation, analyzes Erwan Cordeau, in charge of studies on climate, air and energy at the Paris Region Institute.

“We observe the most mortality when the population is exposed to continuous heat, when it does not come down at night, in cities like Paris or in extremely concrete neighborhoods.”

Pierre Masselot, researcher and co-author of the study

at franceinfo

Economic fragility may also explain excess mortality in general. “In Paris, there are more economic inequalities. A large part of the population is more vulnerable to heat, because it has less access to infrastructure to cool off in the event of a heat wave”, says Pierre Masselot. In order to fight against heat islands this summer, the municipality has been betting since June on a cooling plan, entitled “Paris adapts” : planting of trees, installation of shade structures, increase in the number of fountains and misters, greening of streets, walls and roofs… The municipality also offers a map of cool islands.

“In a few years, the Parisian climate will resemble that of a city like Seville. [dans le Sud de l’Espagne]with extreme heat waves, which will last several consecutive weeks, and possibly heat peaks of 50°C… The challenge is quite simply that Paris remain livable and breathable in the coming years”anticipates Dan Lert, deputy mayor of Paris in charge of ecological transition, climate plan, water and energyin a report on the adaptation of the city to the heat (in PDF)published in April.