The Health Effects of Climate Change

Medical Alert! report explores how climate change is undermining
the health of Americans

Mona Sarfaty

Most Americans cannot name a single health effect from climate change.1 Nevertheless, U.S. physicians are providing medical care to people who are experiencing health problems caused or aggravated by climate change every day. Specific conditions include heat illnesses, aggravated allergies, injuries caused by extreme weather, lung problems due to wildfires and ozone pollution (smog), tick and mosquito borne diseases, and mental health conditions brought on by evacuation or loss due to heavy precipitation and flooding. Nineteen medical societies (and counting) representing more than 550,000 physician groups—more than half the physicians in the United States—have joined together to start a new group: the Medical Society Consortium on Climate and Health. Its mission is to inform the public and policymakers about the health harms of climate change and the health benefits of climate solutions.

In March 2017, the Consortium released a report called Medical Alert! Climate Change is Harming Our Health.2 The report provides information for the public and policymakers about seven climate-related health harms, and it highlights firsthand experiences from four physicians in different specialties in various parts of the country.3

Personal Stories

Virginia pediatrician Samantha Ahdoot talks about the danger of new heat records. She had a personal brush with the impact of hot weather on children when her 9-year-old son ended up in the emergency room (ER) after he fainted at band camp. She realized then that summers are changing and children are at excessive risk. She learned 9,000 high school athletes are treated in the ER for heat illness each year, and young men account for one-third of all heat-related visits.

North Carolina emergency medicine doctor John Meredith was in the ER at Eastern Carolina University during a bog fire in the unusually dry summer of 2008. He noted a rise in respiratory and cardiac complaints and, with other researchers, devised a study that would evaluate his observation.4 He and his colleagues compared ER visits in the counties that experienced the fire’s smoke plume with those that did not. The affected counties had a significant rise in the number of ER visits for an array of lung and heart ailments, including asthma, chronic lung disease, bronchitis, heart attacks and strokes, compared to the counties that did not experience the plume. Fire seasons now start earlier and last longer than they did in the past.5

Louisiana critical care physician Claude Tellis experienced the “1,000-year” rainfall and flood in his hometown of Baton Rouge in August 2016. The Coast Guard, National Guard and local responders rescued 30,000 people, and thousands went to shelters.6 People fled and left their lifesaving medicines behind. Dr. Tellis and other physicians worked with pharmacists to get medicines reissued and delivered to shelters. Six months later, discarded and ruined housing parts and appliances like refrigerators and washing machines were still piled up at curbs waiting for pick up. School children became frightened whenever it rained for fear of another flood.

Rhode Island internist Nitin Damle saw a dramatic rise in tick-borne illnesses in his practice. While he and his partners used to see two to three patients per month with Lyme disease during the warm season, they now see 30 to 40 patients. Other tick-borne diseases have become more common as well. They see babesiosis, erlichiosis and anaplasma—all rarely seen in the past.

Research Findings

Beyond the personal stories, there is an accumulating body of research documenting the many ways climate change is undermining the health of Americans. Unhealthy air quality develops on hotter days and puts breathing at risk—especially for those who have asthma or pre-existing lung disease. When vehicle or industrial emissions and fumes are exposed to heat and light, they undergo chemical transformation and become ozone (smog). Ozone irritates the airways of the lungs, and when enough of it accumulates in the air, an ozone alert may be triggered. This could be a problem for anyone, but people who are most likely to have breathing trouble are the 15 percent of the population who already have a problem.7

An Actuarial Perspective

In 2015, the Society of Actuaries (SOA) established the Climate and Environmental Sustainability Research Committee (CESRC). The purpose of the CESRC is to expand the boundaries of the actuarial profession in this emerging area of practice …

Others are more vulnerable to different climate change effects. Children who spend more time outside, pregnant women whose babies are developing in utero and the elderly whose bodies no longer respond well to heat are all at greater risk on hot days. People who work outside, experience homelessness or have mental health conditions are also at greater risk during heat waves. Increased risk confronts people with fewer financial resources who cannot get out of harm’s way when there is extreme weather.

Botanists say the nutritional value of wheat and other grains is declining as their protein content drops because of higher carbon dioxide concentration in the air.8 In other words, wheat grown under high carbon dioxide conditions is less nutritious. Furthermore, droughts lead to crop decline, resulting in increased prices and greater food insecurity.

Water contamination is also occurring. Around agricultural areas, increases in storm water run-off during heavy rainfall carries dissolved fertilizer (plant nutrients) that can spark harmful algae blooms in large bodies of water that people rely on for their drinking water. The water crisis that occurred in Toledo, Ohio, in 2014 because of the algae bloom in Lake Erie is an example of this.9 When harmful algae blooms occur in recreational lakes, swimming may be banned.

Taking Action

These health harms will get worse unless we act to stop them. That’s why physicians and medical societies have joined forces to speak out and urge action. They offer education to their own members as well as the public and policymakers. The most important actions we can take are to stop wasting energy, increase energy efficiency and accelerate the inevitable transition to clean renewable energy. In addition to limiting climate change, accelerating a transition to clean energy has the added benefit of rapidly cleaning up our air and our water so that we can all enjoy better health. Clean renewable energy choices, like wind and solar, do not pollute the air. They don’t leave coal ash behind that pollutes groundwater with toxic metals, either. And they don’t flow through pipes that burst and foul the landscape.

Americans waste a great deal of precious energy and use far more energy per person than people who have similar lifestyles in European countries, and way more than people around the world. Off-the-shelf energy efficient technologies and appliances could reduce our energy use by 25 to 40 percent. This is a huge savings and has the added benefit of leaving money in our pockets.

There is no longer any doubt that human-caused climate change is happening. Ninety-seven percent of peer reviewed papers published by climate scientists are in agreement about this fact. Thousands of studies with multiple sources of evidence have demonstrated this. Moreover, climate change is harming our health now, in communities across the nation. These harms include heat related conditions, worsening chronic illness, injuries and deaths from dangerous weather events, infectious diseases spread by mosquitoes and ticks, infections from contaminated food and water, and mental health problems.


While the health of any American can be harmed by climate change, some people face greater risk. Children, student athletes, pregnant women, the elderly, people with chronic illnesses and allergies, and the poor are most likely to be harmed. Unless we take concerted action, these harms to our health are going to get much worse. The sooner we act, the more harm we can prevent, and the greater our chances of protecting our people.

Physicians are sharing Medical Alert! with the public and policymakers. They have contacted members of Congress, the National Governors Association, the Conference of Mayors, the White House and Fortune 500 corporations. They are speaking in favor of limiting climate change to the fullest extent possible—so that the harm to the public’s health does not grow further. They are also speaking in favor of sustainability at their workplaces in offices and hospitals. Hospitals and health systems account for 8 percent of greenhouse gases.

Patients trust doctors to safeguard their health. This trust is an important reason to close this gap in public awareness, beginning with this Medical Alert! report. This may seem like an unusual topic for physicians, but climate change has become a very real health problem for many patients. Physicians are sounding the alarm: The ultimate danger of climate change is that it’s a danger to the health of every American.

Mona Sarfaty, M.D., MPH, FAAFP, is the director of the Program on Climate and Health in the Center for Climate Change Communication at George Mason University.


  1. 1. Leiserowitz, Anthony, Edward Maibach, Connie Roser-Renouf, Geoff Feinberg, Seth Rosenthal, and Jennifer Marlon. 2014. Public Perceptions of the Health Consequences of Global Warming. Yale University and George Mason University. New Haven, CT: Yale Project on Climate Change Communication.
  2. 2. The Medical Society Consortium on Climate and Health. 2017. Report: Medical Alert! Climate Change Is Harming Our Health. March 15.
  3. 3. Supra note 2.
  4. 4. Rappold, Ana G., Susan L. Stone, Wayne E. Cascio, Lucas M. Neas, Vasu J. Kilaru, Martha Sue Carraway, James J. Szykman, Amy Ising, William E. Cleve, John T. Meredith, Heather Vaughan-Batten, Lana Deyneka, and Robert B. Devlin. 2011. “Peat Bog Wildfire Smoke Exposure in Rural North Carolina Is Associated With Cardiopulmonary Emergency Department Visits Assessed Through Syndromic Surveillance.” Environmental Health Perspectives 119 (10): 1415–1420.
  5. 5. “Longer, More Frequent Fire Seasons.” 2015. NASA. July 28.
  6. 6. Yan, Holly, and Rosa Flores. 2016. “Louisiana Flood: Worst U.S. Disaster Since Hurricane Sandy, Red Cross Says.” CNN. August 19.
  7. 7. Reinberg, Steven. 2015. “About 1 in 7 Older Adults Has Lung Disease: CDC.” WebMD. January 6.
  8. 8. Myers, Samuel S., Antonella Zanobetti, Itai Kloog, Peter Huybers, Andrew D. B. Leakey, Arnold J. Bloom, Eli Carlisle, et al. 2014. “Increasing CO2 Threatens Human Nutrition.” Nature 510 (7503): 139–42.
  9. 9. Circle of Blue. 2014. “Toxic Algae Bloom Leaves 500,000 Without Drinking Water in Ohio.” EcoWatch. August 3.