Evolution climatique et canicule en milieu urbain : apport de la télédétection à l'anticipation et à la gestion de l'impact sanitaire

rapport finalSummer warming trends in Western Europe are increasing the incidence, intensity and duration of heat waves. These are especially deadly in cities owing to surface properties, anthropogenic heat and pollutants. In August 2003, for nine consecutive days, the Paris metropolitan area experienced an extreme heat wave that caused 4,867 heatrelated deaths. A time series of 84 satellite thermal images, from July 21 to August 21 2003 was used to analyze surface temperature variations and the associated heat stress. Satellite observations indicate significant surface temperature gradients and contrasted daytime / nighttime urban heat island patterns. The relatively small temperature amplitude in reference to a normal summer confirms the impact of high minimum temperatures on the heat wave process, lack of nighttime relief and on the subsequent heat stress and mortality. Maps of temperature thresholds and areas most vulnerable to heat stress were delineated. Thermal indices were produced at the addresses of 482 case studies and were integrated into a regression model to estimate the risk factors of mortality for elderly people during the heat wave. Thermal indices for minimum, maximum, mean surface temperatures and diurnal amplitude were tested on the day of death and 1, 2, 6 or 13 days preceding. Results from the linear regression analysis were statistically significant for minimum temperatures. For an increase of 0.5°C, the death risk can be twice as high. A summertime satellite surveillance is being developed to inform the public and authorities about extreme surface temperatures and related heat stress. This analysis demonstrates the relevance of satellite remote sensing in monitoring heat waves in megacities, in estimating the health impact and implementing alert systems and public health strategies

The Impact of Heat Islands on Mortality in Paris during the August 2003 Heat Wave

Background: Heat waves have a drastic impact on urban populations, which could increase with climate change

La vie humaine en haute montagne

Altitude is one of the few natural constraints to which human response cannot be purely cultural or technological. Most of the high mountain areas are uninhabited, but about 10 million people in tropical latitudes permanently live above 3500 m. The main limiting factors of living so high up are night cold ana the lack of oxygen. Only specific adaptation mechanisms ensure that human organism can survive in such conditions. Moreover this does not rule out a greater incidence of a number of diseases, even if it is sometimes tricky to tell what is under the control of altitude and what is caused by other factors, as a bad socio-economic status. The same assessment applies to the decreasing fertility, that is yet to be proved : instead of less frequent conceptions, it would be better to talk about abnormally frequent miscarriages and still births.L'altitude est l'une des rares contraintes naturelles auxquelles la réponse humaine ne peut pas être uniquement d'ordre culturel ou technologique. La plupart des hautes montagnes sont vides d'hommes, mais aux latitudes intertropicales quelque 10 millions d'individus vivent de façon permanente au-dessus de 3500 m. Les principaux facteurs limitants auxquels la vie se heurte à ces niveaux sont le froid nocturne et la pénurie d'oxygène. Seule l'intervention de mécanismes spécifiques d'adaptation permet de survivre dans de telles conditions, sans que cela exclue une incidence majorée d'un certain nombre de maladies, même s'il est parfois difficile de distinguer ce qui relève de l'altitude et d'autres causes, à commencer par la précarité des conditions socio-économiques. Le constat vaut également pour l'apparente baisse de la fécondité : plutôt que de conceptions espacées, il conviendrait de parler de fausses couches et de mortinatalités anormalement fréquentes.Laaidi Karine, Besancenot Jean-Pierre. La vie humaine en haute montagne. In: L'information géographique, volume 66, n°1, 2002. pp. 1-17

Relevance of Green, Shaded Environments in the Prevention of Adverse Effects on Health from Heat and Air Pollution in Urban Areas

S’adapter à un monde plus chaud est devenu une priorité, particulièrement dans les villes qui combinent une population importante et des conditions d’exposition aggravées par l’îlot de chaleur urbain. Ces villes sont également soucieuses d’améliorer la qualité de l’air. Cet article synthétise et discute les principales connaissances sur l’intérêt de la végétalisation en ville comme outil de prévention des impacts sanitaires de la chaleur et sur les bénéfices potentiels associés, notamment sur la qualité de l’air. La littérature montre que la végétation peut créer des îlots de fraîcheur en ville et réduire localement la température et les concentrations de certains polluants de l’air. Peu d’études épidémiologiques s’intéressent aux répercussions sanitaires possibles, mais elles indiquent un effet protecteur probable de la végétation sur la mortalité et le recours aux soins pendant les vagues de chaleur. Les espaces verts peuvent également contribuer à restaurer et à construire les capacités de résilience des personnes, et à réduire les impacts sanitaires de la chaleur et de la pollution. Les connaissances actuelles permettent de développer des stratégies de végétalisation adaptées pour optimiser les bénéfices en termes de réduction des îlots de chaleur urbains, d’amélioration du confort thermique en hiver, et de qualité de l’air. Les bénéfices sanitaires associés sont potentiellement importants. Seule une partie peut en être quantifiée par les outils actuels d’évaluation des impacts sanitaires.Adaptation to a warmer world is a priority, especially in large urban centres where the population is concen-trated and heat-related risks are compounded by the urban heat island. These cities are also interested in improving their air quality. This paper summarizes and discusses current knowledge on how green spaces may be used to reduce heat-related health impacts and their potential co-benefits, especially for air quality. The literature shows that vegetation contributes to the creation of cool islands in cities, and to locally decreasing temperature and air pollutant concentrations. Few epidemiological studies have investigated the associated health impacts, but what is available indicates that vegetation is probably a protective factor that reduces mortality and morbidity during heat waves. Green spaces can also contribute to restoring and building resi-lience capabilities, thus reducing the health impacts of heat and pollution. Current knowledge provides the material to develop green space strategies adapted to optimize benefits in terms of urban heat island, ther-mal comfort and air quality, generating potentially large health benefits. Only a part of those benefits can be quantified with current health impact assessment tools

Satellite monitoring of summer heat waves in the Paris metropolitan area

11 p.International audienceIn August 2003, for 9 consecutive days, the Paris metropolitan area experienced an extreme heat wave that caused 4867 estimated heat-related deaths. A set of 61 NOAA-AVHRR images and one SPOT-high resolution visible image were used to analyse the spatial variations of land surface temperature (LST) over the diurnal cycle during the heat wave.LSTs were sampled from images at the addresses of 482 elderly people to produce daily and cumulative minimal, maximal and mean thermal indicators, over various periods of time.These indicators were integrated into a conditional logistic regression model to test their use as heat exposure indicators, based on risk factors. Over the period 1–13 August, thermal indicators taking into account minimum nocturnal temperatures averaged over 7 days or over the whole period were significantly linked to mortality. These results show the extent of the spatial variability in urban climate variables and the impact of night-time temperatures on excess mortality

Impact of the 2015 July Heat Waves in France on Heat-Related Causes

Presentation of the impact of two major heat waves occurring in July 2015 in France on heat-related causes in emergency health care facilities, using the French syndromic surveillance system SurSaUD®

Impact of the 2015 July Heat Waves in France on Heat-Related Causes

Presentation of the impact of two major heat waves occurring in July 2015 in France on heat-related causes in emergency health care facilities, using the French syndromic surveillance system SurSaUD®

Has the impact of heat waves on mortality changed in France since the European heat wave of summer 2003? A study of the 2006 heat wave.

International audienceBACKGROUND: In July 2006, a lasting and severe heat wave occurred in Western Europe. Since the 2003 heat wave, several preventive measures and an alert system aiming at reducing the risks related to high temperatures have been set up in France by the health authorities and institutions. In order to evaluate the effectiveness of those measures, the observed excess mortality during the 2006 heat wave was compared to the expected excess mortality. METHODS: A Poisson regression model relating the daily fluctuations in summer temperature and mortality in France from 1975 to 2003 was used to estimate the daily expected number of deaths over the period 2004-2006 as a function of the observed temperatures. RESULTS: During the 2006 heat wave (from 11 to 28 July), about 2065 excess deaths occurred in France. Considering the observed temperatures and with the hypothesis that heat-related mortality had not changed since 2003, 6452 excess deaths were predicted for the period. The observed mortality during the 2006 heat wave was thus markedly less than the expected mortality ( approximately 4400 less deaths). CONCLUSIONS: The excess mortality during the 2006 heat wave, which was markedly lower than that predicted by the model, may be interpreted as a decrease in the population's vulnerability to heat, together with, since 2003, increased awareness of the risk related to extreme temperatures, preventive measures and the set-up of the warning system