World Health Day: The Hazards of Global Warming to Your Health

As thousands of people pour into emergency rooms and millions line up to be vaccinated, Brazil's public health officials and recently even its military are fighting to control vector-borne diseases. Mosquitoes are carrying illnesses like dengue and yellow fever into Brazil's largest cities, including Rio and Brasília, and the tropical disease, chikungunya, previously unheard of in Italy, was reported there last year. The two recent outbreaks in Brazil have caused a total of more than 80 deaths, 57,000 new infections, and widespread panic. As a result of global warming, mosquitoes, ticks, rodents and other vectors are expanding their geographic range and altering long-established patterns of disease. Climate changes worldwide are also causing serious problems with food and water supplies, increasing mental health concerns, and exacerbating air pollution, which elevates chronic disease risk.

Global temperature increases of 0.9°F (0.5°C) over the past century have led to an estimated 150,000 deaths and the loss of 5.5 million disability-adjusted life years (DALYs) annually, with the rates expected to double over the next several decades. The World Health Organization (WHO) has documented 39 new or re-emerging diseases since the 1960's, many linked to global warming -- an explosion of illnesses that has not been seen since the Industrial Revolution when masses of people moved to cities, increasing the spread of disease. Nevertheless, only minimal attention has been paid to one of the most significant yet least publicized hazards of climate change -- its impact on the health of people worldwide. Human health, influenced by a complex system of biological, social, economic, political and geographic factors, is particularly vulnerable to the effects of global warming and has significant humanitarian, economic and national security implications. On World Health Day, it is time to focus international attention on this critical issue.

Many infectious diseases exhibit sensitivity to climate change. Mosquitoes -- the most common disease vectors that spread illnesses such as malaria, dengue, West Nile encephalitis, and yellow fever -- thrive in wet and humid tropical environments. Currently, at least one million people die every year, including 3000 children every day, from malaria. A 3.6-5.4°F increase in global temperatures would cause malaria-carrying mosquitoes to enter new geographic areas, placing millions more people at risk of the disease. Moreover, this is not just a problem for the developing world. Malaria and dengue fever cases have been reported in the United States. West Nile encephalitis outbreaks, linked to warmer temperatures, have been on the rise in America as well. Studies also suggest that the extreme storms of El Niño increased mosquito populations, contributing to a five-fold rise in malaria rates worldwide. As global climate change produces more extreme weather events, such as hurricanes and flooding, spikes in the prevalence of other weather sensitive diseases can be expected. Furthermore, deforestation, a major contributor to global warming, has brought animals and ticks in contact with humans, resulting in the emergence of a new infectious illness, Lyme's Disease, first reported in 1975. Global warming is projected to expand the range of ticks that carry this disease.

The earth's water supply has also been profoundly affected by global warming, endangering the health of people and the planet. Water is essential to all aspects of life, yet 99% of water on Earth is unsafe or unavailable to drink. As a result of global warming, water will become even more scarce and contaminated as climate patterns change, extreme weather events occur, and glaciers melt. The 20th century has witnessed the greatest increase in temperature of any century in the past thousand years, bringing with it a change in precipitation patterns and a rise in sea levels. Global sea levels rose at an average rate of 0.07 inches per year from 1961-2003 (rising at an even greater rate of 0.12 inches per year on average from 1993-2003) reducing fresh water availability and elevating water temperatures that threaten already scarce water supplies. The 2007 Intergovernmental Panel on Climate Change Report projected that the global mean sea level is expected to rise between 7.1 to 23.2 inches by 2100. In many places, a rise in 19.7 inches would cause some beaches to be washed away, and for some islands such as the Maldives, it could mean significant portions of the land being submersed underwater. Furthermore, the combination of extreme weather events and changes in the availability of water affect agricultural food production, destroy botanical sources of natural medicines, incapacitate sewage systems, and result in widespread population displacement, leading to disruptions in acute and chronic disease management with national security implications as well. Some of the world's major conflicts have arisen over disputes concerning arable land and water and these types of tensions may become even more prevalent as resources diminish.