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Health Effects

Weather and climate have affected human health for millennia. Now, climate change is altering weather and climate patterns that previously have been relatively stable. Climate experts are particularly confident that climate change will bring increasingly frequent and severe heat waves and extreme weather events, as well as a rise in sea levels. These changes have the potential to affect human health in several direct and indirect ways, some of them severe.

A brief overview of the likely health effects of increased temperatures and extreme weather events is provided here. Links to additional information about these and other potential health effects − such as air quality, vector-borne and zoonotic diseases, water- and food-borne diseases and mental health − appear below.

Increased Temperatures

Heat exposure has a range of health effects, from mild heat rashes to deadly heat stroke. Heat exposure can also aggravate several chronic diseases, including cardiovascular and respiratory disease. The results can be severe and result in both increased illness and death. Heat also increases ground-level ozone concentrations, causing direct lung injury and increasing the severity of respiratory diseases such as asthma and chronic obstructive pulmonary disease. Higher temperatures and heat waves increased demand for electricity and thus combustion of fossil fuels, generating airborne particulates and indirectly leading to increased respiratory disease.

Over a longer time period, increased temperatures have other effects ranging from drought to ecosystem changes that can affect health. Droughts can result in shortages of clean water and may concentrate contaminants that negatively affect the chemistry of surface waters in some areas. Drought may also strain agricultural productivity and could result in increased food prices and food shortages, worsening strain on those affected by hunger and food insecurity in the U.S. and elsewhere. Ecosystem changes include migration of the vectors (organisms that do not cause disease but transmit infection by carrying pathogens from one host to another) and animal hosts that cause certain diseases prevalent in the U.S., such as Lyme disease and Hantavirus. The dynamics of disease migration are complex and temperature is just one factor affecting the distribution of these diseases.

Winters will also be warmer, which is likely to lead to a decrease in illness and death associated with exposure to cold. In addition to this general warming trend, climate change will bring increased weather variability, the results of which are difficult to predict.

Extreme Weather Events

The direct effects of extreme weather events include drowning from floods, injuries from floods, and structural collapse. Indirect effects outnumber the direct effects and likely will be more costly. Potential indirect effects include aggravation of chronic diseases due to interruptions in health care service, significant mental health concerns both from interrupted care and geographic displacement, and socioeconomic disruption resulting from population displacement and infrastructure loss.

Sea level rise increases the risk from extreme weather events in coastal areas, threatening critical infrastructure and worsening immediate and chronic health effects. Salt-water entering freshwater drinking supplies is also a concern for these regions, and increased salt content in soil can hinder agricultural activity in coastal areas.

Other indirect exposures and health effects

Climate change is a complex phenomenon and a range of unanticipated ecological effects may result. Many of these ecosystem effects could have indirect health effects. Increased concentrations of ground-level carbon dioxide and longer growing seasons could result in higher pollen production, worsening allergic and respiratory disease. Increased carbon dioxide concentrations in sea water may cause oceans to grow more acidic and is likely to contribute to adverse ecosystem changes in the world’s tropical oceans. This would have potentially dramatic implications for fisheries and the food supply in certain regions of the world. Major regional ecosystem stresses may result in mass population movement and conflict, with significant health effects. Some of these concerns are low-probability high-impact events, and could have significant health impacts on a global scale.

Potential Climate Change Health Effects

Additional Readings about the Health Effects of Climate Change

Frumkin H, Hess J, and Vindigni S. Peak petroleum and public health. JAMA. 298:1688-1690, 2007.

Frumkin H, Hess J, Luber G, Malilay J, and McGeehin M. Climate change: the public health response. Am J Public Health. 98:435-445, 2008.

Luber G, and Hess J. Climate change and human health in the United States. J of Env Health. 70(5):43-44, 2007.

Patz JA, McGeehin M, Bernard SM, Ebie KL, Epstein PR, Grambsch A, Gubler DJ, Reiter P, Romieu I, Rose JB, Samet JM, Trtang J. The potential health impacts of climate variability and change for the US. Env Hlth Pers. 108 (4): 36-54, 2000.

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