Climate Impacts: Field of Action Human Health

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Human health can be affected by climate change.
Source: Miss X/

Humans react sensitively to changes in the climate - especially to rising temperatures. Physical performance and bodily well-being can be strongly influenced by heat. Older, more frail and health-impaired people and children are particularly affected by the health risks of climate change.

Health consequences of extreme weather events

As a result of climate change, an increase in extreme weather conditions in Germany is expected. These include an increase in extreme heat waves, storms or heavy precipitation, floods, avalanches or landslides. Direct effects can be diseases and injuries, some of them fatal. Further consequences can be health conditions such as stress, mental disorders, anxiety or depression.

The summers in Germany have also become significantly hotter in all regions and at all altitudes. What was once an extremely hot summer is now an average summer. Even the cooler summers of the last 25 years usually remained well above the long-term temperature average before 1990.

In retrospect, since the 1970s there has been an increasing trend of so-called "hot days", when the daily maximum air temperature is 30 °C or more. This also applies to the so-called "tropical nights", in which temperatures do not drop below 20°C and proper rest and recuperation is then severely limited.

Spread of vector-borne infectious agents

As air temperature rises, carriers of pathogens (so-called carriers, such as ticks or mosquitoes), whose distribution was previously restricted to tropical and subtropical regions, can open up new habitats and thus expand the range of the pathogens they transmit.

It is feared that under future changes in climate conditions in Germany, conditions will be more favorable both for the animal carriers and for the pathogens themselves (such as West Nile virus, dengue- or Q fever). As a result, the risk of infection for humans may also increase. This can also affect domestic carriers and pathogens (e.g. Orthohantavirus).

Changing climatic conditions can influence the interaction of pathogens and carriers in several ways. If climatic conditions change for the animal carrier organisms, changes in behaviour, reproduction rate, life span, population density or choice of habitat may follow. Therefore, milder winters can cause the animals to be active for a longer time of year and reproduce faster. Additionally, it is possible that carrier species not originally native to this country, which are introduced from warm countries, establish and spread here.

The mechanisms responsible for the development of pathogens within carriers and for their transmission to animals and humans are complex and often not yet fully understood.

Extreme weather events such as floods can also benefit the existence of carriers. The Elbe floods of 2002 and 2013, for example, provided ideal conditions for the mass reproduction of mosquitoes.

In Germany, there could be an increased risk of Orthohantavirus, Borrelia and TBE viruses in particular. Orthohantavirus is transmitted by rodents, often by bank voles. It can lead to fever and, in the worst cases, cause kidney failure. The virus is currently particularly widespread in the Swabian Jura, the Bavarian Forest, Lower Franconia and the Osnabrück area. Borrelia or tick-borne encephalitis virus (TBE virus), on the other hand, are transmitted by ticks. Lyme borreliosis is one of the most frequent vector-borne infectious diseases in Germany. TBE risk areas are currently designated in the federal states of Baden-Württemberg, Bavaria, Hesse, Rhineland-Palatinate and Thuringia.

Increasing global trade in goods and tourism can also lead to the unintentional introduction of foreign pathogens by humans or animals, for example through animal and food transport or animal feed or seeds.

Asthma, allergies, sunburn and skin cancer

Due to changed environmental conditions, further health risks such as asthma and allergies can arise as a consequence of climate change. An overall milder climate with a longer vegetation period favors the longer flying times and higher concentrations of pollen. The potency of pollen allergens could also possibly increase with higher temperatures. If it gets warmer, thermophilic plant species that were previously not native to Germany and have a high allergenic potential may also migrate.

The pollen season could therefore start earlier and last longer than a few years ago. An increase in theCO2 concentration in the air can additionally increase pollen production. For people with asthma and hay fever, this prolongs the amount of tie suffering from symptoms. At the same time, allergies triggered by pollen have become much more frequent in Germany in recent years. Newly immigrated plants such as the ragweed (Ambrosiaartemisiifolia), which thrives well under the altered climatic conditions, also contribute to this.

As hot days increase, so do the concentrations of ground-level ozone and particulate matter in the air. Direct health effects of increased ozone concentrations include irritation of mucous membranes, respiratory reactions such as reduced lung function, cardiovascular disease and reduced physical performance.

In particular, increasing summer high-pressure weather conditions could favour the formation of ground-level ozone. This has also been proven to intensify sunshine duration. The short-term effects of increased, unprotected UV radiation include sunburn, corneal disease and conjunctivitis. Long-term, unprotected exposure to UV radiation can lead to skin cancer. However, in Germany the UV radiation only slightly increased in the last decade. A further slight increase is expected in the future.

Heat stress affects health

The effect of extreme heat events on human health depends crucially on their frequency, intensity and duration. In Germany, so-called heat waves in the future will occur more frequently and last longer, as the years 2015 and 2018 recently showed. They can cause extreme heat stress in humans. Stress reduces physical performance, therefore having a negative impact on social productivity in industry and trade.

The human cardiovascular system is particularly affected by extremely high temperatures. Older people are particularly affected, as the adaptation process for thermoregulation of body temperature slows down with age and the ability to release physical heat decreases. Therefore, demographic change increases the risk potential in the population.

In addition, the body's ability to adapt can be impaired by previous illnesses such as diabetes or diseases of the central nervous system, as well as by the intake of medication and consumption of stimulants (alcohol, caffeine, etc.).

In 2003, the heat wave in Germany led to about 7,500 additional deaths from heart attacks, cardiovascular diseases and kidney failure as well as respiratory problems and metabolic disorders. In 2006 and 2015 there were about 6,000 additional heat-related deaths respectively.

Overall, EU countries are expected to experience an increase in mortality of one to four percent per one degree increase in temperature. For Germany, it is estimated that heat-related deaths will increase by more than 5,000 per year between 2071 and 2100. Model calculations show that winter mortality and ice-related injuries are expected to decrease due to milder winters.

Climate change has a negative impact on water quality

The increase in weather extremes such as heavy rainfall, flooding or drought will also affect the quality and availability of drinking water. Mild air and water temperatures, increased solar radiation and higher CO2 concentrations in the atmosphere favor plant growth which, as an example, can lead to an increase in blue-green algae (cyanobacteria) in the Baltic Sea and inland lakes. Since certain blue-green algae produce numerous toxins, the quality of affected waters decreases significantly. In addition, the summer warming of the Baltic Sea with its low tides is also expected to increase the risk of vibrio infections. Health effects are skin irritations or gastrointestinal diseases.

If you are interested in possible adaptation measures in the field of human health, please click here.