Climate change will influence human health in several ways. Impacts will reflect the conditions of the ecological and social environments in which humans live. The impacts of projected changes in climate will depend on current and future public health defenses. Difficult economic conditions during the past decade have had serious implications for the delivery of health care and the public health infrastructure in some countries in CEE. These countries are most at risk from potential health impacts of climate change.
One can expect an increase in the frequency of heat waves, as well as warmer summers and milder winters. Analyses in European cities show that total mortality rises as summer temperatures increase (Katsouyanni et al., 1993; Kunst et al., 1993; Jendritzky et al., 1997). Episodes of extreme high temperatures (heat waves) also have significant impacts on health. Heat waves in July 1976 and July-August 1995 were associated with a 15% increase in mortality in greater London (McMichael and Kovats, 1998; Rooney et al., 1998). A major heat wave in July 1987 in Athens was associated with 2,000 excess deaths (Katsouyanni et al., 1988, 1993). Much of the excess mortality attributable to heat waves is from cardiovascular, cerebrovascular, and respiratory disease, and the elderly are particularly vulnerable to heat-related illness and death (Faunt et al., 1995; Sartor et al., 1995).
In cold and temperate locations, daily deaths increase as daily wintertime temperature decreases (Khaw, 1995; Laake and Sverre, 1996). Based on current evidence, climate change (increase in mean winter temperatures) is likely to result in a reduction in wintertime deaths, at least in temperate countries. Langford and Bentham (1995) estimate that 9,000 wintertime deaths yr-1 could be avoided by the year 2025 in England and Wales under a 2.5°C increase in average winter temperature. A meta-analysis by Martens (1997) estimates that an increase in global temperature could result in a reduction in winter cardiovascular mortality in Europe, leading to a decrease in mortality rates in regions with cold/temperate climates. At this time, the literature does not enable quantitative comparison between changes in summer and winter mortality.
Climate change also is likely to affect air quality in urban areas. Formation (and destruction) of secondary air pollutants, such as ozone, increases at higher temperatures and increased levels of sunlight. Studies in the United States indicate that climate change would entail an increase in average ambient concentrations of ozone and an increase in the frequency of ozone pollution "episodes" (USEPA, 1989). Experiments with the Hadley Centre climate model indicate significant increases in baseline ozone concentrations in Europe. Ozone and other air pollutants have significant impacts on health; these pollutants are considered to be one of the most important environmental health problems in Europe. Finally, climate change is likely to change the seasonality of pollen-related disorders such as allergic rhinitis (hay fever) (Emberlin, 1994).
Climate plays a dominant role in determining the distribution and abundance of insects and tick species-directly, through its effects on vector and parasite development, and indirectly through its effects on host plants and animals and land-use changes (McMichael et al., 1996). Therefore, it is anticipated that climate change will have an effect on the geographical range and seasonal activity of vector species and, potentially, disease transmission (Bradley, 1993; Martens et al., 1997; Martens, 1998).
As a result of deterioration of health systems, the recent resurgence of malaria in eastern Europe is now a growing cause for concern. Climate change could exaggerate this increased risk. In regions of southern Europe, climate change would increase the current very small risk of local (autochthonous) transmission. A few such cases are reported in the Mediterranean area under current climate conditions (e.g., in Italy-Balderi et al., 1998). Concomitant with increases in the volume of international travel, all countries in Europe have seen a steady increase in the number of imported cases of malaria, which provide the source of the pathogen (WHO, 1997). In the UK, however, local vectors are physiologically unable to transmit the most lethal form of malaria (falciparum) (Marchant et al., 1998). Although localized outbreaks are more likely to occur under climate change, in northern and western Europe existing public health resources and a lack of breeding habitats necessary to maintain high densities of mosquitoes make re-emergent malaria unlikely.
Dengue currently is not present in Europe, although it has been present in the past (Gratz and Knudsen, 1996). However, one of the vectors (Ae. albopictus) currently is extending its range in Europe, and climate change could facilitate this expansion (Knudsen et al., 1996). This vector has been reported in Italy since 1990 and in Albania since 1979.
In all countries bordering the Mediterranean, cutaneous and visceral leishmaniasis are transmitted to humans and dogs by phebotomine sandflies (Dedet et al., 1995). Higher temperatures are likely to change the geographical distribution of the important sandfly vector species and accelerate maturation of the protozoal parasite, thereby increasing the risk of infection (Rioux et al., 1985). Increased incidences of visceral leishmaniasis, unrelated to immune suppression, have been reported from regions of Italy and coastal Croatia (Gabutti et al., 1998; Punda-Polic et al., 1998). Several imported cases of canine leishmaniasis are reported in Germany, Switzerland, and Austria every year (Gothe et al., 1997). Thus, imported canine cases are a potential source of the pathogen, if the vectors expand further north with climate change.
Ixodid ticks (e.g., Ixodes ricinus and I. persulcatus) are widely distributed in temperate regions and transmit tick-borne diseases in Europe, of which Lyme disease (Berglund et al., 1995) and tick-borne encephalitis (TBE) are the most important (Tälleklint and Jaenson, 1998). In Sweden, TBE incidence has increased after milder winters, in combination with extended spring and autumn seasons during 2 successive years (Lindgren, 1998). There also is some evidence that the northern limit of the distribution of ticks in Sweden has moved northward between 1980 and 1994 as a result of the increased frequency of milder winters (Tälleklint and Jaenson, 1998; Lindgren et al., 2000). Climate change may extend the length of the transmission season of tick-borne diseases and facilitate spread to higher latitude and altitudes in northern Europe. However, a model-based study indicates that overall the region suitable for TBE transmission may contract significantly (Randolph and Rogers, 2001).
Climate change could have a major impact on water resources and sanitation in situations where water supply is effectively reduced. Some populations in eastern Europe with restricted access to water in the home would be vulnerable to any climate-related decreases in freshwater availability. Decreased water availability also could lower the efficiency of local sewage systems and may necessitate use of poorer quality sources of freshwater, such as rivers. All of these factors could result in an increased incidence of water-borne diseases.
The most significant water-borne disease associated with the public water supply in western Europe is cryptosporidiosis. Increases in the frequency or intensity of extreme precipitation events can increase the risk of outbreaks of this disease. Cases of cercarial dermatitis (water-based parasitic disease) may increase if the climate becomes more favorable for the host-a water snail (de Gentile et al., 1995).
Warmer climate in combination with inappropriate food behavior may contribute to increased incidences of food-borne diseases. A study of food-borne illness in the UK found a strong relationship between incidence and temperature in the month preceding the illness (Bentham and Langford, 1995). The distribution and activity of flies, cockroaches, and rodents could change in response to climatic changes. These species are carriers of food-borne pathogens and are considered to be major hygienic pests in the domestic environment.
The risk of flooding (coastal and riverine) is likely to increase in Europe under climate change. With this risk comes additional risk to people's health as a consequence of flooding (Menne et al., 1999). Some floods in Europe have been associated with an increased risk of leptospirosis-for example, outbreaks were reported following floods in Ukraine and the Czech Republic in 1997 (Kriz, 1998: Kriz et al., 1998) and in Portugal in 1967 (Simoes, 1969). Many cases of post-flood food poisoning were noted during and after the Odra flood in 1997.
Some of the effects of flooding on mortality and ill health in developed countries is attributable to the distress and psychological effects of the event (Bennett, 1970). This was demonstrated in the Easter 1998 flooding in parts of England (the worst since 1947); the majority of flood victims interviewed cited stress associated with the event and post-flood recovery as the worst aspect of their experience (Tapsell and Tunstall, 2000). Cases of post-traumatic stress disorder, including 50 flood-linked suicides, were reported in the 2 months following the major floods in Poland in 1997 (IFRC, 1998). The health effects of flooding are complex and can result from a combination of factors. The impact of flooding on mental health therefore may be significant.
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