The Environmental Effects of Climate Change on Human Health: An Overview
Climate change, defined by the United Nations as “long-term shifts in temperature and weather patterns” due to human activities such as burning fossil fuels in the industrial era, has resulted in profound and ongoing changes in our environment and the health of our planet and humanity (1). Since the dawn of the industrial revolution, the continued acceleration of greenhouse gas emissions due primarily to the burning of fossil fuel has led to rising levels of carbon dioxide and other greenhouses gases, leading to a rise in global mean temperatures. Temperature increases have led to sea level rise, extreme weather events, including flooding, prolonged and more severe heat waves, and worsening drought. These changes in the environment and weather have led to a variety of adverse outcomes including:
- An increase in mortality and morbidity due to heatstroke
- Malnutrition due to crop failure and food insecurity
- Wildfires that expose people to increased air pollution
- Displacement of communities, migration, and civil strife related to profound economic disruptions
Exposure and deleterious outcomes related to these threats will place increasing pressure on community and health care systems infrastructure to adequately respond. Individuals and communities with the fewest socioeconomic resources will be at the highest risk for the environmental effects due to climate change.
Efforts to mitigate damage by weaning off the use of fossil fuel so far have not been successful in moderating global temperatures, so it is expected that these temperature changes will continue to degrade our environment and put humans at risk for deleterious effects on health.
The known and potential effects on human health related to climate change include psychological risks, cardiovascular disease, kidney disease, respiratory and allergic conditions, immune-system dysfunction, and increased susceptibility to infection. Possible adaptive measures can limit risk to human health, especially among individuals with the greatest degrees of vulnerability.
Specific Effects on Human Health Related to Climate Change
Psychological Effects:
Perhaps the most significant effect on human health is psychological. Individuals may experience worsening anxiety, depression, posttraumatic stress disorder (PTSD), and cognitive decline as a result of climate-related exposures that cause profound social disruption, food and water insecurity, and geographic displacement of individuals and communities. Individuals with preexisting psychiatric illness may have exacerbations of their illness due to additional stress and disruptions in health care services due to limited access to medication and health care professionals (2,3).
Cardiovascular Disease:
Cardiovascular effects on human health can occur due to the effects of excessive heat during heat waves when efforts to cool the body lead to excessive heart rate, myocardial demand, and potentially myocardial ischemia and heart failure. Use of beta-blockers and diuretics can alter cardiovascular and renal hemodynamics, limiting adaptive mechanisms, when patients are exposed to acute heat. Wildfire exposure that results in inhalation of small particulate matter (PM) can cause systemic inflammation, leading to vascular inflammation, thrombosis, and ischemia. Epidemiologic data suggest an increased risk of sudden death and myocardial infarction in those exposed to major wildfires (4, 5).
Respiratory and Allergic Disease:
Increased exposure to PM, particularly to fine particulate matter (PM2.5, PM10), due to wildfire smoke and industrial pollution can exacerbate underlying pulmonary disorders such as asthma and chronic obstructive pulmonary disease (COPD). Aeroallergens, such as ragweed, are now found in more expansive geographic locations due to warmer temperatures, which foster their growth and allergenicity. In vulnerable people (eg, those living near industrial areas), the combination of increased allergenicity and air pollution exposure can increase the risk of developing asthma, asthma exacerbations, and other respiratory disorders (6).
Kidney Disease:
Exposure to extreme heat can lead to acute kidney failure due to dehydration. In people with chronic heat exposure (eg, farm workers), extreme heat can contribute to unexplained chronic renal insufficiency (formerly referred to as Mesoamerican nephropathy, after a high burden of disease was observed in agricultural workers in Central America). Disruptions in dialysis and medical services due to extreme weather events can lead to higher rates of hospitalization and death, and delay kidney transplantation (7,8).
Immunologic Disease:
Environmental effects on the immune system related to climate change are poorly understood; however, emerging evidence suggests that pollution, heat stress, and infectious exposures can result in loss of epithelial and gut mucosal integrity, causing an inflammatory cascade that can result in autoimmune disease. Environmental exposure may result in changes in the immune system that lead to de novo autoimmune diseases or possibly exacerbations of existing diseases. Understanding the temporal relationship between exposure and the immunologic effect is challenging; recent epidemiologic evidence has shown an association between the development of rheumatoid arthritis and exposure to PM and nitrogen oxides due to wildfires (9,10).
Infectious Disease:
Increased risk of infections may be linked to migration of pathogens due to climate change. Tick-borne illness, fungal infections, and malaria may become endemic in wider regions. Flooding due to increased storm severity and sea level rise may affect vulnerable populations in low-lowing areas due to water-borne illness leading to diarrhea, dehydration, and malnutrition (11).
Adaptive and Mitigative Strategies
As environmental exposures due to climate become more common and severe, health care professionals will need to understand how to communicate with and help patients and their communities prepare and limit harm, especially among those at highest risk. For example, emerging heat-mapping tools and more accurate weather prediction allow more precise assessment for those areas and individuals at risk for heat effects.
Local health care institutions, local governments, and individual clinicians can develop alert systems to communicate risk and provide adaptive strategies and resources ahead of need.
Well-defined air quality indices can be used to communicate the impending potential for exposure to wildfire smoke and PM to individuals and communities at risk (such as those with COPD or asthma). Public health officials can implement protective strategies such as remaining indoors, using N95 masks, and considering installation of HEPA filters in homes for use during periods of exposure to high levels of air pollution.
Education for patients in zones that are at high risk for storms, flooding, or heat waves will be necessary to guarantee adequate supplies of medications, water, and food as well as back-up power for telecommunication and refrigeration needed for certain medications. More globally, renewable energy sources must be increasingly used, and the health care sector will need to adopt strategies to limit waste and pollution given that health care delivery is a significant contributor to greenhouse emissions in most industrialized countries.
References
1. United Nations Climate Action. What is climate change? United Nations. Accessed October 3, 2025. https://www.un.org/climatechange/what-is-climate-change
2. Nan J, Jaiswal S, Ramanathan D et al. Climate trauma from wildfire exposure impacts cognitive decision-making. Sci Rep 2025;15:11992. doi: 10.1038/s41598-025-94672-0
3. Mishra J, Han H, Ramanathan V. A mental health focus to amplify climate resilience actions. npj Clim Action 2025; 4:55. doi: 10.1038/s44168-025-00263-0
4. Kazi DS, Katznelson E, Liu CL, et al. Climate Change and Cardiovascular Health: A Systematic Review. JAMA Cardiol 2024;9(8):748-757. doi: 10.1001/jamacardio.2024.1321
5. Braunwald E. Cardiovascular effects of climate change, Eur Heart J. 2024;45(33):3006–3008. doi: 10.1093/eurheartj/ehae401
6. Burbank AJ. Climate Change and the Future of Allergies and Asthma. Curr Allergy Asthma Rep. 2025;25:20. doi: 10.1007/s11882-025-01201-0
7. Young SE, Khoshnaw LJ, Johnson RJ. Climate and the Nephrologist: The Intersection of Climate Change, Kidney Disease, and Clinical Care. Clin J Am Soc Nephrol. 2023;18(3):411-417. doi: 10.2215/CJN.08530722
8. Remigio RV, Jiang C, Raimann J, et al. Association of extreme heat events with hospital admission or mortality among patients with end-stage renal disease. JAMA Netw Open. 2019;2(8):e198904. doi:10.1001/jamanetworkopen.2019.8904
9. Miller FW. Environment, Lifestyles, and Climate Change: The Many Nongenetic Contributors to The Long and Winding Road to Autoimmune Diseases. Arthritis Care Res. 2025;77(1): 3-11. doi: 10.1002/acr.25423
10. Kronzer VL, Yang Y, Roul P, et al. Associations of Fire Smoke and Other Pollutants With Incident Rheumatoid Arthritis and Rheumatoid Arthritis-Associated Interstitial Lung Disease. Arthritis Rheumatol. 2025;77(7):808-816. doi: 10.1002/art.43113
11. Mora C, McKenzie T, Gaw IM, et al. Over half of known human pathogenic diseases can be aggravated by climate change. Nat Clim Chang. 2022;12(9):869–875. doi:10.1038/s41558-022-01426-1