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How climatic change affects human health

Updated on March 8, 2015

Climatic change contributes to the outbreak of vector-borne diseases

According to Knowlton (2010), global climatic change poses a threat to people’s health by contributing to the outbreak of water-borne diseases such as cholera, dengue. This is because there are various ways via which climatic changes result to the exacerbation of waterborne illnesses For instance, an increase in temperatures by 4°C (7.2°F) leads to increased rainfall intensity. The later results to the occurrence of floods that cause water to stagnate everywhere. The presence of stagnant water provides proper breeding spots for insects and other organisms that transmit diseases. Moreover, it is commonly known that mosquitoes use stagnant waters to breed and transmit malaria. Therefore, a sudden increase in temperatures reduces the incubation periods for water born and vector diseases. The later increases the rate at which vector and waterborne diseases are transmitted because it increases the populations of the disease vectors. Alternatively, some vectors do not need high temperatures to hatch. In fact, they breed under low-temperature conditions. In the light of this, a decrease in temperature will still increase the rates at which disease vectors hatch and burden the human populations with many illnesses.

Climate change leads to the outbreak of waterborne diseases

Knowlton also believes that climatic changes such as floods and rise in sea levels result in the contamination of drinking waters (2010). This is because runway waters wash away all the sewage and other human-related wastes and dump them in other water sources during periods of heavy rains. Because the hygiene is at minimum levels during these moments, the less fortunate people are forced to cook with and ingest these contaminated waters because they cannot afford to treat it. They also lack the capabilities of boiling or distilling these waters. The later leads to an increased transmission of water pathogens and diseases. Soon or later, they start suffering from various illnesses as characterized by nausea, vomiting, skin rashes, fever, headaches, diarrhoea and other body problems. Overly, these diseases worsen the health of human beings and serves as threats to their survival.

Climate change causes respiratory and cardiovascular diseases

Changes in weather conditions such as wind, temperature and humidity may lead to both cardiovascular and respiratory diseases because they affect the ambient quality of air. Climatic related environmental factors such as rainfalls, winds, dust storms and temperatures amplify the ambient concentrations of ground-level ozone and aeroallergens (dust and pollen grains) which are the main causatives of respiratory diseases. For instance, in Egypt, 340000 deaths and 15000 bronchitis infections arise from air pollution caused by desert storms and humid air. These dust storms are caused by change in wind patterns resulting from severe temperature changes. Similarly, cardiovascular related illnesses are caused by factors related to adverse climatic changes. For instance, changes in average daily temperatures lead to other vital physiological changes within the body. These comprise of blood viscosity, blood pressures and rates of heartbeats that are directly associated with stroke and other cardiovascular diseases. The author also states that 2070 to 4760 cases of respiratory illnesses reported in the United Arabs Emirate, Syria, Lebanon, Egypt and Kuwait are as a result of temperature changes arising from climatic changes


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Severe climate changes cause gene mutations and may lead to birth defects

Severe climatic changes may also interfere with people’s genetic compositions and lead to their mutations. According to Verner (2012), many of the increased rates of birth defects witnessed here on earth are as a result of climatic changes among other factors. This is because adverse climatic changes such as rainfalls and temperatures increases the levels of toxins such as pesticides in the environment and leaves individuals vulnerable to these toxins. Consequently, the early development stages of human beings such as foetal formation, birth and childhood are susceptible to the effects of these toxins. During these delicate stages of human development, exposure to toxins induces malfunction defects through the mechanisms of epigenetic changes and genetic mutations (Verner, 2012). The later leads to the delivery of children with severe defects; hence negatively impacting their health. In order to prove how climatic changes result in genetic mutations, Verner quotes the example of Arab countries whereby the total annual birth defects are estimated to be 43520. 43520 is a 7% estimation of the total number of illnesses occurring within the Arab countries. This 7% population of congenital anomalies is caused by factors emanating from climatic changes such as changes in weather, soil salinity and water acidity (Verner, 2012).

Climate change affects peoples’ health by causing food poisoning

Severe climatic changes also affect people’s health by promoting factors that lead to food poisoning. For instance, they promote the growth of algae blooms that are poisonous when ingested by humans. In the light of this, climatic change forces sea temperatures to rise to abnormal temperatures. This creates favourable environments for the growth of harmful algae blooms. At relatively higher temperatures, harmful algae blooms grow well and attract fish species. Being a typical food for fish and other marine animals, the fish consume the harmful and poisonous algae. Consequently, fishermen trap these poisoned fish while fishing and offer them to the markets for sale. Once people purchase and consume these fishes, they suffer from food poisoning (Verschuuren, 2013). The most common type of fish poisoning occurring to due to climatic change are Ciguatera and Scombroid.


Ciguatera is the most recurrently reported disease caused by harmful algal blooms (HABs). It is endemic in Caribbean and South Pacific regions where the consumption of reef fish is common. People suffering from Ciguatera fish poisoning are classically described as initially exhibiting gastrointestinal symptoms followed by neurologic symptoms. In severe cases, Symptoms of cardiac arrests are also exhibited by the victims of Ciguatera food poisoning (Verschuuren, 2013). Additionally, the affected individuals may continually reveal chronic neurologic symptoms even after periods of their health recovery. To elaborate further the concepts of Ciguatera food poisoning, Verschuuren (2013) states that the Ciguatera disease is caused by the ingestion of tropical reef fishes that have accrued potent neurotoxins (ciguatoxins) in their viscera and flesh. He also continues to explain how neurotoxins flow from the algae to Pisces; and later to human beings. According to Verschuuren (2013), Ciguatoxins have their origins in precursor compounds called gambier toxins produced by Gambierdiscus genus dinoflagellates, a type of microalgae. Gambier toxins undergo the process of biotransformation to ciguatoxins while moving through coral reef trophic levels from herbivorous to large carnivorous fish (Verschuuren, 2013). While at the carnivorous stage, the already poisoned fish eventually get consumed by humans. Therefore, the author states that climatic changes in terms of heat waves and rise in sea temperatures negatively impact the health of people by making them vulnerable to food poisoning.


Scombroid affects people in a global sphere because it occurs both in tropical and temperate waters. Its infection occurs after the consumption of poorly preserved or refrigerated fish containing high levels of histamine (Hungerford, 2010). It symptoms range from mild to severe allergic reactions. Fishes that are typically associated with Scombroid infections contain naturally high levels of histidine accumulated in their flesh after sea temperatures change (Hungerford, 2010). Examples of fishes that have been determined to accumulate high levels of Scombroid comprise of herring, dolphin fish, tuna, marlin, bluefish, anchovy, amberjack, and sardine. Bacterial overgrowth in poorly stored fish convert Histidine into histamine (Hungerford, 2010). Overly, these histamines cause allergic reactions when people consume infected fish because they are resistant to freezing, cooking, smoking and canning.

Other food poisoning arising from sea toxins

Apart from the Ciguatera food poisoning, there are other sea toxins that arise in the oceans due to temperature and acidity changes. These toxins are carried by shellfish. Once ingested by humans, they cause severe gastrointestinal illnesses. They comprise of:

i. Paralytic shellfish poisoning. This is a fatal disease whose effects are seen two hours after consuming affected fish. In affects the nervous system and may cause life term paralysis (Ansdell, 2013).

ii. Diarrhetic shellfish poisoning. This infection cause diarrhoea and vomiting. It is also accompanied by other gastrointestinal symptoms that arise two to three after the consumption of affected fish.

iii. Amnesic shellfish poisoning. This is yet another fatal disease that occurs one hour after consuming affected fish. The infection kills the nervous systems, cause coma and may lead to acute death (Ansdell, 2013).

iv. Neurotoxic shellfish poisoning. This disease exhibits symptoms that are similar to that of Ciguatera. However, their effects last shortly, ranging between 2 hours and 3 hours after the consumption of affected fish.

Climate change lowers crop, livestock and marine production

Severe climatic changes also affect the health of people by affecting the quality and quantity of food products. This is because various climatic factors such as periodic floods, droughts and stresses emanating from high heat waves may lead to a decline of both crop and livestock productivity (The US Environmental Protection Agency, 2013). For instance, regions that have already been severely affected by drought such as Sahel- in Africa- and Australia have experienced a reduction in the available water for irrigation. Because these countries have been heavily relying on crop irrigation, crop yield have declined leading to food shortages (The treasury of Great Britain, 2007). Moreover, cereal crops yield more at mid to high latitudes. However, this depends on the type of crops grown and local rates of global warming. For the case of Sahel, the rates of global warming and temperature rises have exceeded the maximum temperatures at which cereal crops yield more. The increased heat waves have served to stress the cereal crops, leading to a reduction in their annual yield (The US Environmental Protection Agency, 2013). At lower latitudes such as in Australia, cereal crops reduce their yields due to the extreme reductions in temperatures.

Furthermore, global climatic changes have already affected many fisheries across the globe. This is because shifts in climates have resulted in increased sea temperatures. Consequently, some marine species have migrated to the cooler waters that reside outside of their normal range. Their migration has caused severe food shortages because they are vital for the supply and growth of many countries and their economies. The later has resulted to starvation and cases of ill health in many countries due to malnutrition. For instance, more than 47 million people in the Lower Asian Mekong delta thrive on the fisheries (The US Environmental Protection Agency, 2013). Additionally, according to the EAP report (2013), reductions and rises in sea levels together with their water flows negatively affect water quality. Consequently, fish species in the region decrease either due to migration or death. This would negatively impacts the supply of food for the neighbouring communities that have already grown dependent on these natural resources. The later leads to a poorly fed population whose health is susceptible to diseases (The US Environmental Protection Agency, 2013). Logically, diseases and ill heath are bound to thrive more in poorly fed populations than those that are fed well.

Climate change promotes poverty and ill health

There are also other indirect ways via which adverse climatic changes affect people’s health. This is because it promotes various factors that promote increased poverty rates and later overburden them with ill health. Firstly, floods cause water stagnation and prevent people from undertaking any economic activity (Renton, 2012). Secondly, floods may kill or worsen the health of livestock. This results to a decrease in the overall livestock production. Thirdly, severely climatic changes such as droughts and famines affect agricultural productivity. The later results to decreased products, food shortages, low incomes and increased rates of poverty. Thirdly floods may also destroy properties and people’s houses. Fourthly, severe climatic changes such as intense heat waves and ultraviolet sun radiations inflict diseases and suffering in people (Renton, 2012). This reduces the number of individuals capable of providing productive labor. The later results to an impoverished nation that is unable to care for citizens (The treasury of Great Britain, 2007). Because of the high rates of poverty, lack of financial power and poor environments, medical services become rare. At such rates of poverty, it becomes very difficult to cloth, shelter, feed people and provide them with the right medical treatments. Overly, these factors promote poor health and make people susceptible to diseases. The later results to high cases of ill-health and high mortality rates.


In conclusion, there are many ways via which climate change negatively affects people’s health. It leads to food poisoning such as Ciguatera and Scombroid fish poisonings, causes genetic mutations promoting cancer and causes respiratory diseases. It also contaminates drinking water, promotes the spread of waterborne diseases and cause cardiovascular diseases. Adverse climate changes also cause famine, floods and increase poverty rates. Overly, these effects promote ill health among people.


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