The climate crisis may be the most critical public health problem of this century. 70 U.S. healthcare organizations including the American Medical Association, the American Academies of Family Practice and Pediatrics, and the American Heart and Lung Associations endorsed a report about public health and climate change titled “U.S. Call to Action on Climate, Health, and Equity: A Policy Action Agenda.” Human actions have increased the global mean surface temperature by 1°C (1.8°F) thus far and will continue to raise temperature by 0.1 – 0.3°C (0.2 – 0.5°F) per decade if greenhouse gas emissions continue. These changes in temperature will massively impact public health in a number of ways.
As ocean temperatures rise, tropical storms become larger, more powerful, and cause more rainfall. Many of these events are happening now. This year has seen record heat waves across the U.S., Europe, and Greenland; floods in the U.S. Midwest; and wildfires in Alaska, Siberia, Greenland, and the Western United States. In 2017 and 2018, there were unusually powerful and large hurricanes such as Harvey (Texas), Florence (North Carolina), Maria (Puerto Rico), and Irma (Florida and Caribbean). Lyme disease and West Nile virus encephalitis have been spreading north from the U.S. into Canada as warmer temperatures make survival easier for ticks and mosquitoes. As the tropics expand towards the poles, diseases carried by mosquitoes follow. The Middle East (Southwest Asia) may become too hot for human habitation. Coastal cities such as Jakarta, Indonesia; Mumbai, India; Shanghai, China; London, U.K.; Miami, New Orleans, and New York may become uninhabitable due to sea level rise.
Heat, droughts, and floods are reducing agricultural harvests. Longer warm seasons and warmer temperatures are expected to augment the numbers of insect agricultural pests. Hunger and undernutrition may increase worldwide. Fresh water may be compromised by contamination with floodwater, by blooms of toxic algae, or by salt intrusion from rising seas. Floods often introduce bacteria and toxins into sources of drinking water. For example, floodwaters from hurricane Florence contaminated fresh water with animal manure from farms and with toxic coal ash from power plants. Droughts may reduce available fresh water from lakes, rivers, and aquifers.
Heat-related illness such as hyperthermia (heat stroke) and heat-related kidney disease will increase particularly among outdoor workers and the elderly. Diseases exacerbated by air pollution such as asthma, heart disease, and chronic pulmonary disease may also be made worse by high heat and humidity. Mental illness such as anxiety, post-traumatic stress, and depression may become even more prevalent. Diseases carried by mosquitoes and ticks such as Lyme disease, dengue fever, zika virus infection, and malaria are already becoming more widespread geographically. Climate-related disasters such as floods, fires, or hurricanes may overwhelm health care, agricultural, and drinking water infrastructure. Water contamination due to microorganisms in flood waters (Campylobacter, Salmonella, Vibrio cholerae, Cryptosporidium) or toxic algae may cause outbreaks of diarrheal illnesses.
In addition to warmer ocean water, there is ocean acidification caused by CO2 emissions. Carbon dioxide from the atmosphere dissolves into and combines with water to form carbonic acid. Carbonic acid makes the ocean more acidic (lowers ocean water pH). As our actions add more CO2 to the atmosphere, ocean pH declines. Some organisms will have difficulty surviving. For example, corals, mollusks, and oysters have less ability to make shells as pH falls. If these organisms cannot survive, organisms that depend on them also may die. In general, the more acidic the ocean becomes, the fewer sea organisms can survive. Ocean water warming and acidification not only harm sea life, but also are likely to harm humans by reducing ocean harvests.
The World Health Organization estimates that, without efforts to mitigate climate change, 250,000 persons will die from climate change each year from 2030 to 2050. At the present time six to nine million premature deaths are caused by pollution each year. These deaths are predominantly due to exacerbations of heart and pulmonary disease in countries with severe air pollution.
Recognizing and acting on climate change improves the health of every person in the world and diminishes threats to future generations. Each person can be an effective steward by reducing their individual use of fossil fuels and petroleum products and by participating in collective efforts to replace fossil fuels and plastics with renewable resources. Our response will determine the state of human health for centuries to come. If people from wealthy nations act to reduce climate change and require their governments to act, the climate crisis can be averted.