Climate change affects public health in many ways – increasing heat exposure, expanding the range of disease vectors, worsening food and waterborne illnesses, and causing air pollution. These changes can impact people’s physical and mental health.
They can also increase costs for healthcare systems. Some people are at higher risk, including vulnerable populations like the elderly and those living in poverty.
Increased Heat-Related Illnesses
As the climate warms, the risk of heat-related illnesses will increase. These illnesses include acute respiratory and cardiovascular diseases, mental health impacts, and more.
While most people can adapt to incremental increases in average temperatures, some groups will be at greater risk for adverse health effects. These include small children, older adults, communities of colour, and those living below the poverty line. Additionally, those whose jobs require outdoor work and people with chronic diseases or social isolation may be especially vulnerable.
In addition to increasing the incidence of these illnesses, warmer weather will allow mosquitoes and other disease-carrying insects to thrive in new areas. This will lead to an increased risk of the spread of diseases like malaria, dengue, and Zika.
Cities will be particularly vulnerable as they experience multiple hazards such as extreme heat, air pollution and urban flooding. Wellcome is supporting research into how to best help communities adapt to these challenges, particularly in the most affected areas.
Spread of Vector-Borne Diseases
A warmer climate is creating more places where disease-carrying mosquitoes, ticks, and fleas can survive and breed. These vectors then carry pathogens like West Nile Virus, dengue fever, malaria, and Lyme disease to humans.
Warmer temperatures increase vector competence, meaning that they can grow faster and reproduce more. This increases the likelihood of outbreaks, particularly when naive hosts are present. Moreover, increased transmission rates drive selection for new variants of viruses with greater epidemic potential.
The impacts of climate change on human health are complex and often disproportionately affect vulnerable populations, such as minorities, low-income communities, infants and children, older adults, and pregnant women. Therefore, it is important to consider both the immediate and long-term ramifications of climate change when planning adaptations to improve public health.
Developing indicators of climate change and environmental public health impact is an important first step in this effort. These indicators are quantitative summaries of the relationship between climatic factors and human health outcomes, including mortality and healthcare service use. However, the most accurate and comprehensive approach to assessing these impacts involves disaggregating indicators by country and region and also accounting for social determinants of health (e.g., income, gender, race or ethnicity, disability, occupation, and age).
Air Pollution-Related Health Effects
Many of the health impacts of climate change are related to air pollution and will continue to get worse unless there is an urgent international response to reduce emissions. People’s exposure to and vulnerability to these threats will depend on where they live, how sensitive they are to climate hazards, and their ability to adapt to them.
The effects of climate change on air quality include longer warm seasons and higher levels of airborne pollen, which can make hay fever or allergies much worse; higher levels of carbon monoxide, produced when fuel is burned in vehicles and heating systems; increased ground-level ozone, made when nitrogen oxides and volatile organic compounds react with sunlight; and more frequent and intense wildfire smoke.
These changes can also increase the risk of waterborne illness from contaminated drinking water, as storms and floods can disrupt sewage treatment plants and lead to overflowing streams and rivers. This risk is particularly high for vulnerable populations, including those living in low socioeconomic neighbourhoods and communities, infants and children, older adults, and those with preexisting heart or lung disease.
Food and Waterborne Illnesses
Climate change is increasing the risk of food and waterborne illnesses, as well as changing the transmission routes for vector-borne diseases. This includes a rise in the number of people who are exposed to disease-carrying mosquitoes, as the warmer weather makes them more comfortable, and an increase in the range of places where they can breed.
Warmer temperatures also make it easier for viruses like Zika and dengue to spread. And changes in the weather patterns can lead to the contamination of drinking water with parasites such as Giardia and Cryptosporidium, which are more likely to grow when water is stored for longer periods of time or becomes hotter, as in a drought.
A recent review of 94 systematic reviews found that the majority of studies suggested that climate change is associated with adverse health outcomes, mostly in the form of increased infectious diseases or mortality. However, there are some important gaps in the evidence, particularly around psychosocial outcomes. We need further research to identify, understand and communicate the impacts of climate change on human health.
Mental Health Impacts
Mental health encompasses an individual’s emotional, psychological and behavioural well-being, as well as their social functioning. Climate change is creating stressors that can negatively affect mental health, particularly for vulnerable groups like children and the elderly.
The resulting stress can lead to an increased risk of depression, anxiety and other mental illnesses or aggravate existing ones. Moreover, the effects can be felt even by people not living directly at the centre of climate disasters and extreme weather events.
Moreover, the resulting disruptions in social and community structures can make it difficult to access mental health care, especially in rural communities. In addition, the financial and logistical burdens of rebuilding or repairing infrastructure, losing belongings, and coping with displacement can further compound mental health impacts.
A growing number of studies are exploring the links between climate change and mental health, but most reports show limited or conflicting evidence. A more systematic and collaborative approach is needed to identify, communicate, and harness research on this topic towards effective intervention strategies.
Vulnerable Populations at Risk
Few organizations have a greater responsibility for public health and the societal mandate to protect people from harm than healthcare systems. That’s why experts say that viewing climate change as a health threat is so important.
Most studies indicate a negative impact of climate change on multiple adverse health outcomes. However, the extent to which a population is affected varies according to its inherent sensitivity, exposure, and adaptive capacity (see Figure 4).
The most vulnerable are people already struggling with a variety of issues, including poverty, lack of access to health care, or physical or mental illness. These include individuals in poorer neighbourhoods, people of colour, the elderly, and those with preexisting conditions.
Jalonne White-Newsome, an APHA member and senior program officer at the Kresge Foundation, saw this firsthand while caring for her elderly grandparents in Detroit during summertime heat. Her grandparents had a wide range of health problems, and the heat made them worse. “It was heartbreaking to see them suffer,” she says. But she was also inspired to take action and work on addressing the impacts of climate change on health.
Healthcare System Strain and Adaptation
When natural disasters strike, health systems face enormous strain and stress. Hospitals are overcrowded, staffing is disrupted, and supplies of essential medications and equipment are limited or in short supply. These impacts are particularly acute for populations that depend on public-funded healthcare and community resources, like children, the elderly, ethnic minorities, those with underlying medical conditions, and low-income communities.
Flooding can contaminate drinking water with harmful bacteria, and floodwaters may contain heavy metals or chemical pollutants that can make people sick. Droughts and wildfire smoke can interfere with breathing and aggravate respiratory and cardiovascular problems.
Climate change also harms mental health through loss of home and property, injury or death, displacement, and chronic stress. Surveys indicate that many patients lack awareness of how climate change is harming their own health. It’s up to healthcare organizations to educate their patients.
Conclusion
The health impacts of climate change are wide-ranging and exacerbate existing health inequities. It jeopardizes progress towards universal health coverage (UHC) and aggravates barriers to accessing essential healthcare services, such as water, sanitation, food and shelter.
The climate crisis is affecting people globally, but the severity of the impact varies across geographic regions and populations. It is mainly caused by human activity, including burning fossil fuels like coal and oil, cutting down forests, and raising livestock. These activities add enormous amounts of carbon dioxide and other greenhouse gases to the atmosphere, causing global warming.
These gases also aggravate air pollution, which is linked to several health effects, such as respiratory and cardiovascular problems. It also increases the risks of floods, droughts, and wildfires. In addition, it alters the geographical range of mosquitoes and ticks that carry diseases like malaria, dengue, Zika, and Lyme disease. In addition, it increases the amount of pollen in the air, triggering allergic reactions and asthma attacks. Moreover, it reduces the availability of safe drinking water and threatens the supply of adequate nutrition in poor communities.
