Health Effects of Climate Change

The consequences of climate change — including more frequent and intense severe weather, heat, drought and flooding extremes, changing patterns of vector-borne diseases, and threats to food and water security — can have significant impacts on public health. These impacts range from immediate threats to physical safety to long-term effects on mental health and societal wellbeing. As climate change intensifies, its impacts on public health are expected to persist for longer periods of time, occur at unprecedented times of the year, and expand into areas that have never experienced these threats before.1 

Intense Heat

Heat causes more deaths in the U.S. than any other weather-related hazard2 — estimates suggest that approximately 12,000 Americans die of heat-related causes annually, and more than 80 percent of these victims are over 60 years old.3 As humid heat extremes become more frequent due to climate change, scientists predict that related health impacts will increase accordingly, leading to tens of thousands of additional heat-related premature deaths every summer.4 Common heat-related illnesses include heat stroke and exhaustion; heat stress can also cause or exacerbate cardiovascular and kidney problems.5

Extreme Weather Events

Extreme weather events exacerbated by climate change — including drought, heavy rainfall, floods, and intense hurricanes that feed off of warm ocean waters— cause death, injury, illness, worsening of underlying medical conditions, and adverse effects on mental health.6 Hurricanes Harvey and Maria, for example, killed thousands of people in Houston and Puerto Rico, respectively.7 As extreme weather events become more frequent and intense, these risks to public health are expected to worsen. 

Chemical Safety

Chemical safety is a major public health concern at all times, but especially during extreme weather events. Extreme weather events can dislodge harmful chemicals from soil, homes, industrial waste sites and other sources, and disperse them into the air and water.8 Excessive flooding caused by Hurricane Harvey in 2017 led to multiple fires and explosions at a chemical plant in Crosby, Texas. More than 200 nearby residents were forced to evacuate and 21 emergency responders sought medical treatment after being exposed to the combusted chemicals.9 An investigation of the disaster conducted by the U.S. Chemical Safety Board revealed that, although these types of severe weather events are becoming more intense and frequent, there is a significant lack of guidance in planning for flooding and other severe weather events in the chemical industry.10 

After Hurricane Maria in 2017, researchers in Puerto Rico found elevated levels of polychlorinated biphenyls (PCBs), a suspected carcinogen, in residents of a bayside town. The researchers hypothesized that PCBs from former industrial sites nearby washed into the bay and the surrounding area during the hurricane, exposing residents who survived the storm to PCB-contaminated fish and air.11

In Westlake, Louisiana, a fire at a chemical plant began when Hurricane Laura hit in 2020. The fire released smoke containing chlorine, nitrogen oxide, and other toxins that can be extremely dangerous when inhaled, leading authorities to shut down the interstate highway near the facility, issue stay-at-home orders for nearby residents, and instruct residents to close doors and windows to avoid inhaling the smoke.12

Superfund Sites

According to the Government Accountability Office, the effects of climate change pose a threat to 60 percent of the Superfund sites that are scattered across the U.S.13 Particularly concerning for public health are the effects of flooding caused by hurricane storm surges and sea level rise, which can wash out and expose nearby residents to dangerous toxic 

substances. For example, floodwaters from Hurricane Harvey compromised the containment of hazardous chemicals at the San Jacinto Waste Pits Superfund site in Houston, Texas. Floodwaters from Hurricane Irene in 2011 caused the release of the cancer-causing agent benzene beyond the protective barriers of the American Cyanamid Superfund site in New Jersey. Scientists predict that extreme coastal flooding caused by climate change will pose a risk to more than 900 Superfund sites within the next 20 years.14

Health Care

Extreme weather events also exacerbate existing public health problems by disrupting critical health care systems and infrastructure. During Hurricane Sandy in 2012, six hospitals and 26 residential care facilities in New York City were closed, and thousands of residents who are reliant on home nursing, personal care attendants, medical equipment, and refrigeration for maintaining medications were affected by flooding and loss of power.15

In Puerto Rico, researchers found that interruptions to the island’s medical care systems led to a sustained high mortality rate in the months following Hurricane Maria in 2017.16 One week after the hurricane made landfall, only 11 of the island’s 69 hospitals had power or fuel, and six months after, one in 10 permanent health centers lacked consistent electricity.17 The rapid increase in the number of health care workers leaving the island after the hurricane and a lack of funding at both the federal and local levels has prevented the island from rebuilding much of its health care infrastructure, even three years after the hurricane.18 


As the planet warms, wildfires are becoming more frequent and intense worldwide. In the U.S., wildfires burned more than twice as much land area between 2000 and 2018 as they did between 1985 and 1999.19 Wildfires not only present an immediate safety risk to local residents, but also threaten the health of more distant communities, even those thousands of miles away,20 through exposure to harmful air pollutants found in wildfire smoke, which include particulate matter, ozone, and carbon monoxide.21 Health effects associated with wildfire smoke range from minor eye, nose, and throat irritation to hospitalization and death from severe respiratory issues.22

Infectious Diseases

As the planet warms, diseases carried by vectors, such as mosquitoes, ticks, and fleas, are expected to become more widespread.23 Climate change is altering the geographic range and prevalence of disease vectors that thrive in warm climates, exposing a growing portion of the U.S. population to ticks that carry Lyme disease and mosquitoes that transmit West Nile, chikungunya, dengue, and Zika viruses.24 Researchers have predicted that the number of cases of Lyme disease in the U.S. will rise an estimated 20 percent by mid-century.25 Of 244 U.S. cities studied by a team of researchers at Stanford University, 94 percent have seen an increase in the number of “disease danger days” during which residents are at a heightened risk of contracting diseases spread by mosquitoes.26 

Food Security

The effects of climate change — including extreme weather, exposure to pathogens and pest infestations, and rising levels of carbon dioxide — pose a serious threat to food security in the U.S.27 Floods, droughts, and storms can cause significant damage to crop fields and warmer temperatures can inhibit the growth of certain crops, including corn.28 Scientists have predicted that U.S. corn production could fall by 18 percent by 2100 if global temperatures 

rise by 2°C — or worse, by 50 percent if global temperatures rise by 4°C.29 High temperatures can also increase the risk of crops being exposed to pathogens and toxins that cause foodborne illnesses, and elevated levels of carbon dioxide can diminish the nutritional quality of food by reducing concentrations of dietary iron, zinc, protein, and other important nutrients. These impacts will disrupt food supply chains, reduce access to food, and increase food prices.30

Water Security

High temperatures and heavy rainfall and flooding due to climate change pose a threat to water quality and security in the U.S. Warming water temperatures and increased stormwater runoff triggered by more frequent and intense rainfall can foster harmful algae blooms and introduce toxic pathogens to both recreational waters and drinking water.31 Damage to aging water and sewage infrastructure caused by more severe storms and flooding also jeopardizes access to adequate clean drinking water. Just this summer, 3,700 gallons of sewage spilled into a river in North Carolina as a result of intense rain during Tropical Storm Isaias.32 Researchers predict that by 2100, Chicago will experience a 50 to 120 percent increase in overflow events where stormwater drainage systems are overwhelmed and untreated sewage flows into neighboring water bodies.33

Mental Health 

Climate change can have serious consequences for mental health. Weather-related disasters can cause a range of mental health issues, from short-term stress and increased alcohol and tobacco use, to chronic anxiety, depression, post-traumatic stress, and suicide. The mere threat of climate impacts and related uncertainty can also contribute to anxiety and depression.35 In addition, heat can affect mental health and cause mood changes and an increase in aggressive behavior.36 

Mental health treatment after severe weather events and disasters is important to ensuring that these symptoms do not persist, but federal programs meant to aid survivors struggling with mental health issues only reach a fraction of those who need help. Since Hurricane Harvey in 2017, researchers found that 50 percent of Houston-area residents suffered from powerful or severe emotional distress, yet 70 percent of survivors reported they did not receive mental health treatment.37 Mental health problems that go untreated can linger long after a disaster, as evidenced by a study conducted 12 years after Hurricane Katrina hit Louisiana in 2005, which revealed that one in five low-income mothers affected by the storm still suffered from post-traumatic symptoms.38


1Allison Crimmins et al., Tʜᴇ Iᴍᴘᴀᴄᴛs ᴏꜰ Cʟɪᴍᴀᴛᴇ Cʜᴀɴɢᴇ ᴏɴ Hᴜᴍᴀɴ Hᴇᴀʟᴛʜ ɪɴ ᴛʜᴇ Uɴɪᴛᴇᴅ Sᴛᴀᴛᴇs: A Sᴄɪᴇɴᴛɪꜰɪᴄ Assᴇssᴍᴇɴᴛ (2016), 

2Weather Related Fatality and Injury Statistics, Nᴀᴛɪᴏɴᴀʟ Wᴇᴀᴛʜᴇʀ Sᴇʀᴠɪᴄᴇ (2019), 

3Seniors at Risk: Heat and Climate Change, Cʟɪᴍᴀᴛᴇ Cᴇɴᴛʀᴀʟ (June 24, 2020), 

4Crimmins et al., supra note 1, at 45. 

5Samantha Harrington, How climate change threatens public health, Yᴀʟᴇ Cʟɪᴍᴀᴛᴇ Cᴏɴɴᴇᴄᴛɪᴏɴs (Aug. 19, 2019), 

6Kristie L. Ebi et al., Human Health, in Iᴍᴘᴀᴄᴛs, Rɪsᴋs, ᴀɴᴅ Aᴅᴀᴘᴛᴀᴛɪᴏɴ ɪɴ ᴛʜᴇ Uɴɪᴛᴇᴅ Sᴛᴀᴛᴇs: Fᴏᴜʀᴛʜ Nᴀᴛɪᴏɴᴀʟ Cʟɪᴍᴀᴛᴇ Assᴇssᴍᴇɴᴛ, Vᴏʟᴜᴍᴇ II 14 (2018), 

7CNN Editorial Research, Hurricane Statistics Fast Facts, CNN (updated June 2, 2020),  

8Christopher Flavelle, ‘Toxic Stew’ Stirred Up by Disasters Poses Long-Term Danger, New Findings Show, N.Y. Tɪᴍᴇs (July 15, 2019), 

9U.S. Cʜᴇᴍɪᴄᴀʟ Sᴀꜰᴇᴛʏ ᴀɴᴅ Hᴀᴢᴀʀᴅ Iɴᴠᴇsᴛɪɢᴀᴛɪᴏɴ Bᴏᴀʀᴅ, Exᴛʀᴇᴍᴇ Wᴇᴀᴛʜᴇʀ, Exᴛʀᴇᴍᴇ Cᴏɴsᴇǫᴜᴇɴᴄᴇs: CSB Iɴᴠᴇsᴛɪɢᴀᴛɪᴏɴ ᴏꜰ ᴛʜᴇ Aʀᴋᴇᴍᴀ Cʀᴏsʙʏ Fᴀᴄɪʟɪᴛʏ ᴀɴᴅ Hᴜʀʀɪᴄᴀɴᴇ Hᴀʀᴠᴇʏ (2018), 

10Extreme weather led to chem plant fire, hazmat release, Iɴᴅᴜsᴛʀɪᴀʟ Sᴀꜰᴇᴛʏ ᴀɴᴅ Hʏɢɪᴇɴᴇ Nᴇᴡs (May 29, 2018), 

11Flavelle, supra note 8.

12Nick Miroff, Hurricane Laura strikes Louisiana as Category 4 storm, battering Lake Charles area and bringing flood threat, Wᴀsʜ. Pᴏsᴛ (August 27, 2020),

13Gᴏᴠᴇʀɴᴍᴇɴᴛ Aᴄᴄᴏᴜɴᴛᴀʙɪʟɪᴛʏ Oꜰꜰɪᴄᴇ, Sᴜᴘᴇʀꜰᴜɴᴅ: EPA Sʜᴏᴜʟᴅ Tᴀᴋᴇ Aᴅᴅɪᴛɪᴏɴᴀʟ Aᴄᴛɪᴏɴs ᴛᴏ Mᴀɴᴀɢᴇ Rɪsᴋs ꜰʀᴏᴍ Cʟɪᴍᴀᴛᴇ Cʜᴀɴɢᴇ (2019),

14A Toxic Relationship: Extreme Coastal Flooding and Superfund Sites, Cᴇɴᴛᴇʀ ꜰᴏʀ Sᴄɪᴇɴᴄᴇ ᴀɴᴅ Dᴇᴍᴏᴄʀᴀᴄʏ ᴀᴛ ᴛʜᴇ Uɴɪᴏɴ ᴏꜰ Cᴏɴᴄᴇʀɴᴇᴅ Sᴄɪᴇɴᴛɪsᴛs (2020),

15Lessons Learned from Hurricane Sandy and Recommendations for Improved Healthcare and Public Health Response and Recovery for Future Catastrophic Events, Aᴍᴇʀɪᴄᴀɴ Cᴏʟʟᴇɢᴇ ᴏꜰ Eᴍᴇʀɢᴇɴᴄʏ Pʜʏsɪᴄɪᴀɴs (2015),

16Nishant Kishore et al., Mortality in Puerto Rico after Hurricane Maria, 379 N. Eɴɢʟ. J. Mᴇᴅ. 162 (2018),

17Matt Kurht, Puerto Rico’s healthcare system slowly recovering 6 months after Hurricane Maria, Fɪᴇʀᴄᴇ Hᴇᴀʟᴛʜᴄᴀʀᴇ (Mar. 20, 2018),

18Catherine Kim, A 13-year-old’s death highlights Puerto Rico’s post-Maria health care crisis, Vᴏx (Feb. 27, 2020),

19The Connection Between Climate Change and Wildfires, Uɴɪᴏɴ ᴏꜰ Cᴏɴᴄᴇʀɴᴇᴅ Sᴄɪᴇɴᴛɪsᴛs, (last updated Mar. 11, 2020).

20See, Michael Kodas & Evelyn Nieves, The Fires May be in California, but the Smoke, and its Health Effects, Travel Across the Country, Iɴsɪᴅᴇ Cʟɪᴍᴀᴛᴇ Nᴇᴡs (Aug. 27, 2020),

21John R. Balmes, Where There’s Wildfire, There’s Smoke, 378 N. Eɴɢʟ. J. Mᴇᴅ. 881 (2018),


23Crimmins et al., supra note 1, at 131.

24Ebi et al., supra note 6, at 545.

25Igor Dumic & Edson Severnini, “Ticking Bomb”: The Impact of Climate Change and the Incidence of Lyme Disease, 2018 Cᴀɴᴀᴅɪᴀɴ Jᴏᴜʀɴᴀʟ ᴏꜰ Iɴꜰᴇᴄᴛɪᴏᴜs Dɪsᴇᴀsᴇs ᴀɴᴅ Mᴇᴅɪᴄᴀʟ Mɪᴄʀᴏʙɪᴏʟᴏɢʏ (2018),

26Mosquito Disease Danger Days, Cʟɪᴍᴀᴛᴇ Cᴇɴᴛʀᴀʟ (Aug. 8, 2018),

27Ebi et al., supra note 6, at 546.

28Harrington, supra note 5.

29Rene Cho, How Climate Change Will Alter Our Food, Cᴏʟᴜᴍʙɪᴀ Uɴɪᴠ. Eᴀʀᴛʜ Iɴsᴛɪᴛᴜᴛᴇ (July 25, 2018),

30Ebi et al., supra note 6, at 546.

31Id. at 545.

323,700 gallons of sewage spills in N.C. amid rain from Isaias, E&E Nᴇᴡs (Aug. 5, 2020),

33Harrington, supra note 5.

34Ebi et al., supra note 6, at 546.

35Harrington, supra note 5.

36Ebi et al., supra note 6, at 546.

37Dean Russell & Jamie Smith Hopkins, Disasters are Driving a Mental Health Crisis, Cᴛʀ. ꜰᴏʀ Pᴜʙ. Iɴᴛᴇɢʀɪᴛʏ (Aug. 25, 2020),