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Climate change is causing adverse health impacts and premature deaths worldwide. The Intergovernmental Panel on Climate Change (IPCC), a United Nations research body, emphasized the link between climate and public health in its 2022 report on climate impacts, adaptation, and vulnerability. For North America specifically, the IPCC stated that infectious diseases, heat, malnutrition, mental health, and displacement are all adversely impacted by climate change (see graphic) and will be at an increasing rate.
Source: IPCC 6th Assessment Report Working Group II (Impacts, Adaptation and Vulnerability) Summary for Policy Makers Figure 2
Not only does climate change result in more frequent and severe occurrences of these familiar health threats, but it could also generate unanticipated health threats. For example, the scientific community suspects that thawing permafrost caused by climate change unearthed an infected reindeer carcass in Siberia, Russia, causing an unusual anthrax outbreak. Researchers are concerned that smallpox and other dormant viruses may also lie encapsulated in permafrost, and could potentially be unleashed by warming temperatures.
The health of humans and the health of the planet are deeply connected. Addressing climate change will help address public health threats.
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Although every American is at risk of experiencing adverse health impacts due to climate change, certain populations are more vulnerable due to heightened sensitivity, increased exposure, or reduced adaptive capacity. Although every American is at risk of experiencing adverse health impacts due to climate change, certain populations are more vulnerable due to heightened sensitivity, increased exposure, or reduced adaptive capacity.
Various climate hazards can affect these groups differently, depending on where they live. For example, children of color in the Southern Great Plains are 77% more likely than white children to live in the areas most at risk of seeing increased childhood asthma rates because of climate change. Pregnant individuals everywhere face a high degree of sensitivity to extreme heat, but those in heat-prone areas like the Western United States are frequently exposed to conditions that increase the risk of heat-related illness, preterm birth, and stillbirth. A resurgence of the Zika virus caused by climate change—virus-carrying mosquitoes thrive in warmer, wetter weather—could increase severe fetal brain defects in the Southeast.
Extreme temperatures and weather events are increasing in frequency and severity as a result of climate change. Extreme climate-related events such as hurricanes and heat waves can result in physical injury, cardiovascular failure, hypothermia, heat exhaustion, heatstroke, and death. These events can also cause peripheral impacts during disaster preparation and post-event cleanup activities. As the frequency, intensity, duration, and location of weather events shift, certain regions will experience new climate threats and unfamiliar health problems.
In the United States, the top weather-related public health hazard is extreme heat. By the mid-21st century, the number of people exposed to extreme heat conditions and the frequency of their exposure are expected to increase considerably across the United States. Extreme heat and drought—both of which are amplified by climate change—create the conditions for more frequent wildfires and an extension of wildfire season. On top of the risk of burns, injuries, or deaths as a direct result of wildfires, the smoke produced is a dangerous mixture of air pollutants like particulate matter and mercury, which present additional health risks to surrounding communities. Exposure to wildfire smoke can cause both short- and long-term health impacts, including but not limited to: lung damage and disease; exacerbation of heart disease; impairment of speech, hearing and walking; and preterm birth.
Scientists are still working to quantify the extent to which infectious diseases—which originate from a pathogen (such as a virus or bacteria) and are transmitted by an infected person, animal, or contaminated surface to a susceptible host—are worsened by climate hazards. A 2022 study published in Nature Climate Change found that 58% of all infectious diseases known to have impacted humans in recorded history are aggravated by climate change. The study noted that this documented pattern of disease aggravation happens because climate change hazards tend to 1) bring pathogens and people in closer proximity to each other, 2) strengthen the virulence and accelerate the life cycle of pathogens, and 3) weaken the human capacity to avoid or fight pathogens.
A robust understanding of animal health is of particular importance in the effort to protect human health. Zoonotic diseases—which originate in animals before spreading to humans—account for an estimated 60% of all human pathogens and 75% of emerging infectious diseases. Some notable examples of zoonotic diseases include viruses such as Ebola, human immunodeficiency virus (HIV), and Zika, as well as avian flu and Lyme disease. Warming temperatures can allow these diseases to expand their geographical ranges. For example, researchers predicted in a 2020 study that, by 2050, 1.3 billion more people could live in areas where Zika can spread because of climate change. These newly vulnerable areas would likely include parts of the United States. Prior to 2014, cases of Zika virus were practically unheard of in the United States, but two large outbreaks occurred in 2015 and 2016.
The impacts of climate change on food production, nutrition, prices, and trade in the United States and around the world are profound. Over the next century, climate change is projected to affect food availability, limit access to food, and make farming more difficult as global temperatures rise and cause weather patterns to change. Furthermore, higher concentrations of carbon dioxide in the atmosphere can reduce the nutritional value of a number of widely consumed crops such as wheat, rice, and potatoes. The main factors affecting food security are foodborne bacteria, water scarcity, chemical contaminants, and disruptions in emergency distribution, most of which are exacerbated by climate change. For example, because bacteria grow more rapidly in warmer environments, the presence of bacteria-related food illnesses will likely increase, contributing to both gastrointestinal distress and death.
Rising temperatures can contribute to higher accumulations of mercury in marine life, posing an increased health risk to people who eat seafood. Fish in warmer water have a higher metabolic rate, causing them to eat more but grow less. This is problematic because industrial pollution has led to elevated levels of mercury in streams and oceans, which contaminates fish food sources. If this trend continues over time, people will ingest increasing amounts of mercury even if they do not increase the amount of seafood in their diets. Mercury exposure is especially dangerous for children because it can impair their development. Furthermore, research on the Grassy Narrows First Nation in Canada suggests there may be a correlation between mercury poisoning and increasing rates of attempted suicide among youths.
As climate change increases the frequency and severity of extreme weather events, roads and waterways can become damaged, limiting the opportunities for post-disaster assistance, such as food distribution, to reach communities. Food distribution following severe weather can be particularly challenging in remote and island communities like Puerto Rico that are largely dependent on imported supplies.
Climate change hazards—both immediate and gradual—are already causing mental and emotional distress. This is of great concern in the United States where the National Alliance on Mental Illness suggests that nearly half of the 60 million adults and children living with mental health conditions do not receive treatment. As climate change worsens, children, the elderly, and women are more likely than others to experience mental health issues, although no one is entirely free of the risk.
Post-traumatic stress disorder (PTSD) is perhaps the most well-documented mental health outcome following climate-related disasters. According to a 2021 analysis by the American Psychological Association and ecoAmerica, Hurricane Harvey left at least one in four affected Houston residents with symptoms meeting the diagnostic criteria for PTSD three months after the storm hit in 2017. That same year, Hurricane Maria devastated Puerto Rico, with PTSD rates estimated six months later at about 44% for Puerto Ricans displaced within the island and about 66% for those who fled to Florida after the storm. In addition to PTSD, extreme climate events are linked to higher rates of anxiety, depression, sleep disruption, and suicidal thoughts. Chronic mental distress can have a negative impact on a person’s physical health and immune system response, which, in turn, makes them more susceptible to disease and other ailments.
The production of fossil fuels—coal, oil, and natural gas—is directly damaging to human health in addition to being damaging to the climate and environment. The extraction, transportation, burning, and leaking of fossil fuels result in the release of harmful pollutants into the air. Fine particulate matter (a primary component of air pollution) from fossil fuel combustion is linked to almost one in five deaths worldwide, killing more people each year than HIV, tuberculosis, and malaria combined. In the United States alone, over 100,000 premature deaths can be attributed to human-generated fine particulate matter annually. Some of the most common health impacts attributed to this carcinogen include aggravated asthma, respiratory infections, lung cancer, heart disease, stroke, and cognitive impairment. In addition to releasing fine particulate matter, fossil fuel systems also release about a third of U.S. methane emissions, which can result in ground-level ozone, or smog. Smog is responsible for approximately one million premature respiratory deaths globally every year.
Facilities that process fossil fuels are more likely to be located near overburdened and under-resourced communities typically made up of low-income, minority, or Indigenous populations. Researchers found that non-Hispanic white communities in the United States are exposed to 17% less air pollution than what they emit through their consumption. Black and Hispanic communities, on the other hand, are exposed to 56% and 63% more pollution, respectively, than their own emissions. This racial disparity is exemplified by a stretch of land in Louisiana known as “Cancer Alley,” home to a predominantly Black and low-income community whose cancer risk is nearly 50 times higher than the national average due to the over 200 chemical plants, oil refineries, and other industrial facilities in the area. During the height of the global coronavirus pandemic, these disproportionate levels of air pollution contributed to some of the underlying health conditions that made exposure to the disease more deadly for people of color in the United States.
In order to combat health effects exacerbated or caused by climate-related events on a national level, improvements in emergency preparation and response are essential. Most emergency management should occur before disaster strikes, with a focus on equitable pre-disaster funding and preparedness. Large-scale investments in climate-resilient infrastructure can help prevent injury during extreme events and also facilitate better emergency medical response and food distribution in their aftermath.
Meanwhile, a more localized public health response could take into consideration specific impacts associated with regional climate trends. For example, the extreme heat and drought afflicting the American West calls for policies focused on dehydration, heat stroke, and cardiovascular disease. This is especially true for the Northwest, where high temperatures have been uncommon until recent years and people are therefore more affected by heat because of the lack of infrastructure to deal with it.
Source: U.S. Global Change Research Program, “The Impacts of Climate Change on Human Health: A Scientific Assessment”
Solutions to food insecurity and malnutrition should involve the prioritization of sustainable agriculture. Local resources can be sustainably managed through soil and water conservation, rehabilitation of irrigation systems, and preservation of biodiversity. In addition to food safety and security, sustainable agriculture is also an effective preventative measure against zoonotic diseases. Policies and practices that support the harmonious coexistence of humans, domesticated livestock, and local ecosystems, such as the One Health philosophy supported by the Centers for Disease Control and Prevention, can be particularly impactful tools for disease prevention.
The protection of biodiversity through policies that promote the conservation of key wildlife species and the restoration of their habitats will also be an important step in preventing future pandemics of zoonotic origin. Wildlife conservation programs have the added benefit of offering people the opportunity to interact more with the natural world, which can have positive impacts on mental health. It is essential that climate policies and mental health systems be developed synergistically, and with special consideration for the most vulnerable populations.
Investing in clean sources of energy—including solar, wind, geothermal, hydropower, and biomass—catalyzes the transition away from a fossil fuel economy while also addressing the public health disparities stemming from air pollution. This is a win-win for the climate and our communities. Reducing or eliminating fossil fuel subsidies would help to reinforce the advancement of clean energy technologies and the transition to a more sustainable, equitable, and healthier society.
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