As time passes, scientists have witnessed several developments to the world as we know it. Yet, none has caused as much of a concern as climate change. Climate change is often thought of in terms of its effects on our physical environment: melting ice caps, rising sea levels, heat-waves, and storms. But increasing evidence shows that the human impact—particularly the impact on human health—will be a major challenge for scientists, politicians and ordinary people in years to come. Effects will vary by age, gender, geography, and socioeconomic status—and so will remedies. A recent international study in the Lancet says that many more people will be exposed to extreme weather conditions over the next century than previously thought—“a potentially catastrophic risk to human health” that could undo 50 years of global health gains. The precise extent of the impact is difficult to quantify exactly because there are so many different factors at play. But one thing is certain: climate change is having an effect, and as the planet warms up, that effect is only going to increase. Here are 9 ways climate change can impact our health.
1. More allergies
Studies show that allergies are on the rise in developed countries, which could be due, in part, to rising carbon dioxide levels and warming temperatures. Warmer temperatures and higher concentrations of carbon dioxide in the atmosphere stimulate some plants to grow faster, mature earlier, or produce more potent allergens. These can trigger asthma, which affects around 300 million people. Common allergens such as ragweed also seem to respond particularly well to higher concentrations of carbon dioxide, as do pesky plants such as poison ivy. A more recent study in Italy found that not only had pollen levels increased in the area, but the populations’ sensitivity to pollen had increased as well. While genetics plays a large role in all allergies, a longer and more intense pollen season could exacerbate symptoms.
The impact on malnutrition is more indirect, but comes as a result of climate change’s effect on human society and economic development. Rising temperatures and variable precipitation are expected to reduce crop yields in many tropical developing regions, where food security is already a problem. Cycles of drought and flood in West Africa are making it harder and harder to subsistence farmers to grow enough food to feed their families. And when the rain does come, it washes the topsoil away, degrading the land, so it becomes even more difficult to cultivate crops in the future. This will increase the prevalence of malnutrition—which causes millions of deaths each year—from both a lack of sufficient nutrients to sustain life and a resulting vulnerability to infectious diseases such as malaria, diarrhea, and respiratory illnesses.
3. Mental health
While a person’s physical well-being could be negatively affected by the outcomes of climate change, so too can an individual’s mental health. In particular, experiencing an extreme weather event can result in higher levels of stress, depression, post-traumatic stress disorder and anxiety, particularly when a person loses loved ones or their home. In developing countries, where the impacts of climate change are at their most severe, there is less access to mental health services, so symptoms go untreated and unchecked. Additionally, even the perceived threat of climate change (e.g. from reading or watching news reports about climate change) can influence stress responses and mental health. Individuals with mental illness are especially vulnerable to extreme heat as well; studies have found that having a pre-existing mental illness triped the risk of death during heat waves. People taking medication for mental illness that makes it difficult to regulate their body temperature are particularly at risk.
4. Natural disasters
Projected changes in temperature and precipitation under global warming are likely to lead to other effects that threaten human health and safety. Globally, the number of reporter weather-related natural disasters has more than tripled since the 1960s. Sea levels are rising around the world due to a higher temperature within the Earth’s core that is melting the polar ice caps. Rising sea levels increase the risk of coastal flooding, and could cause population displacement. More than half of the world’s population now lives within 60 kilometres of shorelines. Rising sea levels and increasingly extreme weather events will destroy homes, medical facilities and other essential services. People may be forced to move, which in turn heightens the risk of a range of health effects, from mental disorders to communicable diseases. Floods contaminate freshwater supplies, heighten the risk of water-borne diseases, and create breeding grounds for disease-carrying insects such as mosquitoes.
In addition, emergency evacuations pose health risks to older adults, especially those with limited mobility who cannot use elevators during power outages. Some individuals with disabilities may also be affected if they are unable to access evacuation routes, have difficulty in understanding or receiving warnings of impending danger, or have limited ability to communicate their needs.
5. Water scarcity
More variable rainfall patterns are likely to compromise the supply of fresh water. Rainfall and humidity play a role in spreading infectious diseases, and can cause issues if fecal pathogens are found in a community’s water supply. Furthermore, these transmitters may increase even more after a period of drought, causing an even larger outbreak of a particular infectious disease, according to a study published in Environment International.
Globally, water scarcity already affects 4 out of every 10 people. Water scarcity encourages people to transport water long distances and store supplies in their home. This can increase the risk of household water contamination, causing illnesses. A lack of water and poor water quality can compromise hygiene and health, which includes an increased risk of diarrhea, as well as trachoma (an eye infection that can lead to blindness) and other illnesses.
6. Extreme heat
Heat and drought are amongst the deadliest natural disasters. A study that reviewed weather disasters in the US since 1980 found the top two killers were heat waves and the drought that comes with them. And heat waves may be getting worse. Increasing concentrations of greenhouse gases lead to an increase to both average and extreme temperatures. This will cause increased levels of illness and death by compromising the body’s ability to regulate its temperature. Loss of internal temperature control can result in a cascade of illnesses, including heat cramps, heat exhaustion, heat stroke, and hyperthermia in the presence of extreme heat. Exposure to extreme temperatures can also worsen chronic conditions such as cardiovascular, respiratory, cerebrovascular diseases, and diabetes-related conditions.
Excessive heat is more likely to affect populations in northern latitudes where people are less prepared to cope with excessive temperatures. Certain communities are more vulnerable than others: for example, outdoor workers, homeless people and low-income households who spend more time outdoors and may lack access to air conditioning. Additionally, young children, pregnant women, older adults, and people with medical conditions are less able to regular their body temperature and can therefore be more vulnerable to extreme heat.
7. Poor air quality
Changes in the climate affect their air we breathe, both indoors and outdoors. Three key ingredients—sunlight, warm air, and pollution from power plants and cars burning coal and gasoline—combine to produce ground-level ozone (O3) and fine particulate matter, which can worsen air quality. Wildfires, which are expected to continue to increase in number and severity as the climate changes, create smoke and other unhealthy air pollutants. Increasing carbon dioxide levels also promote the growth of plants that release airborne allergens (see point 2). These changes to outdoor air quality and airborne allergens also affect indoor air quality as both pollutants and aeroallergens infiltrate homes, schools, and other buildings. This can lead to asthma attacks and other respiratory and cardiovascular health effects. Longer pollen seasons can increase allergic sensitization and asthma episodes and thereby limit productivity at work and school.
8. Vector-borne diseases
While individuals may struggle in extreme heat, many infectious illnesses thrive in warmer temperatures. Certain vector-borne diseases in which a host organism, such as an insect, carries and transmits a disease-causing agent are particularly affected by varying weather and hotter temperatures. Climate change lengthens the transmission season and expands the geographical range of many vector-borne diseases like malaria and dengue. Because these vectors are cold-blooded, they rely on their surrounding environment to control their internal heat. So, an increase in temperature would potentially favor insect life, and possibly allow the spread of certain diseases, such as malaria, into new areas.
9. Water-related illnesses
Climate change is expected to affect fish and marine water sources in ways that will increase people’s exposure to water-related contaminants that cause illness. Climate change increases the risk of illness through increasing temperature, more frequent heavy rains and runoff, and the effects of storms. Water-related illnesses are caused by pathogens, such as bacteria, viruses, and protozoa, which flourish in warmer oceans. Water-related illnesses are also caused by toxins produced by certain harmful algae and cyanobacteria and by chemicals introduced into the environment by human activities.
Changing water temperatures mean that waterborne Vibrio bacteria and harmful algal toxins will be present in the water or in seafood at different times of the year, or in places where they were not previously threats. Runoff and flooding resulting from increases in extreme precipitation, hurricane rainfall, and storm surge will increasingly contaminate recreational water bodies (lakes and beaches), shellfish harvesting waters, and sources of drinking water.
People can become ill if exposed to contaminated drinking or recreational water. Exposure occurs through ingestion, inhalation, or direct contact with contaminated water and through consumption of contaminated fish and shellfish. Health impacts may include gastrointestinal illness like diarrhea, effects on the body’s nervous and respiratory systems, or liver and kidney damage.