Climate Fact: Hot Days, Heat Waves and Health

Is it getting hot in here? Rising temperatures and prolonged periods of heat can affect our health in many ways.

Hot Days and Heat Waves: The U.S. average temperature has increased 1.3 to 1.9 degrees Fahrenheit since 1895, and temperatures have risen more quickly since the late 1970s – seven of the 10 warmest years on record for the United States occurred since 1998. Over the past few decades, unusually hot summer days have become more common in the United States. The rate of occurrence of hot summer nights has increased even faster, and the frequency of heat waves – three days with temperatures above 90 degrees Fahrenheit for most parts of the United States – doubled during the 20th century. Heat waves are the number one cause of weather-related deaths due to heat stroke and related conditions.

Heat waves have also increased the number of hospital admissions for cardiovascular, respiratory and kidney disorders. Young children, older adults, people with medical conditions and the poor are the most vulnerable to heat-related illness. Know how to protect your health health during extreme heat events.

Heat, Air Quality and Allergies: Health risks from heat waves and air pollution are not independent. Ground-level ozone pollution forms under hot and stagnant conditions. Breathing ground-level ozone reduces lung function, damages the inner lining of the lungs and increases hospital admissions for asthma, among other health impacts. People who spend time outdoors and are physically active – including children, outdoor workers and athletes – are most vulnerable. Warmer temperatures also increase wildfire risk, which intensifies air pollution. In addition to impacting the areas where fires are burning, wildfire particles can travel thousands of miles, affecting indoor and outdoor air quality. Lastly, higher temperatures have been associated with longer pollen allergy seasons in the United States. Ragweed pollen season has extended by as much as 27 days in northern parts of the North American heartland, resulting in a longer allergy season. Monitor the air quality where you live to protect your health.

Infectious Diseases: Warm temperatures can increase the number of cases of infectious diseases. Some bacteria that infect humans, such as Salmonella, grow faster in warmer environments. It has also been documented that higher temperatures have influenced the spread and distribution of West Nile virus in North America. Scientists found a correlation between above-average temperatures and the spread of West Nile virus into the western United States. In laboratory experiments, scientists recorded that higher temperatures increase the viral load in mosquitoes that transmit the disease and shorten a portion of the mosquitoes’ incubation time. Protect yourself  from West Nile Virus.

Image courtesy NOAA’s National Weather Service (NWS) Collection

(Source: Kunkel, K.E. (2014, March 5) Telephone Interview; Peterson, T.C. et. al. 2013. Monitoring and Understanding Changes in Heat Waves, Cold Waves, Floods and Droughts in the United States: State of Knowledge. Bulletin of the American Meteorological Society. 94:821-834; Melillo, Jerry M., Terese (T.C.) Richmond, and Gary W. Yohe, Eds., 2014: Climate Change Impacts in the United States: The Third National Climate Assessment. U.S. Global Change Research Program, 841 pp. doi:10.7930/J0Z31WJ2; Anderson, G.B. and M.L. Bell. 2011. Heat Waves in the United States: Mortality Risk during Heat Waves and Effect Modification by Heat Wave Characteristics in 43 U.S. Communities. Environmental Health Perspectives 119: 210-218; Environmental Protection Agency. U.S. and Global Temperature. Accessed online 2 April 2014. http://www.epa.gov/climatechange/science/indicators/weather-climate/temperature.html; United States Global Change Research Program. 2009. Global Climate Change Impacts in the United States. Cambridge University Press 196 pp.; Environmental Protection Agency. Climate Change: Basic Information. Accessed online 2 April 2014. http://www.epa.gov/climatechange/basics/; Soverow, J.E., G.A. Wellenius, D.N. Fisman, and M.A. Mittleman. 2009. Infectious Disease in a Warming World: How Weather Influenced West Nile Virus in the United States (2001 – 2005). Environmental Health Perspectives 117(7):1049-1052; Environmental Protection Agency. Climate Impacts on Human Health. Accessed online 2 April 2014. http://www.epa.gov/climatechange/impacts-adaptation/health.html; Easterling, D.R., J.L. Evans, P.Ya. Groisman, T.R. Karl, K.E. Kunkel, P. Ambeje. 2000. Observed Variability and Trends in Extreme Climate Events: A Brief Overview. Bulletin of the American Meteorological Society 81(3):417-425)

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