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Global warming may harm human health

November 16, 1998
Web posted at: 2:10 PM EDT

By Environmental News Network staff

Malaria is spread by the mosquito Anopheles gambiae. Analyses show malaria outbreaks outside tropical regions becoming more common in the future   

Climatic changes related to global warming could foster dangerous outbreaks of cholera, dengue fever and malaria, according to a report released recently by World Wildlife Fund. Children and the elderly would be particularly vulnerable.

Climate experts and environmental officials from 180 countries are currently meeting in Buenos Aires, Argentina, to agree on a work plan for implementation of the 1997 Kyoto protocol, signed by developed countries in Japan last December. The WWF report was issued on the first day of the conference.

"There are strong indications that a disturbing change in disease patterns has begun and that global warming is contributing to them," said the report's author, Dr. Paul Epstein, Associate Director of the Harvard Medical School's Center for Health and the Global Environment.

According to the report, the spread of infectious diseases has accelerated not only because the world is warming, but because nighttime temperatures are rising faster than daytime temperatures. This has particularly disturbing implications for human health because the range of many disease-transmitting insects is limited chiefly by nighttime temperatures.

Diseases like dengue and malaria are affecting new populations as warmer conditions allow mosquitoes to survive over a wider area and at higher altitudes. Dengue fever -- a flu-like illness which can be fatal and for which there is no vaccine -- blanketed Latin America in 1995. It has been recorded in northern Argentina and Australia and is now occurring regularly in Asia.

In fact, mosquitoes carrying dengue fever have invaded more than a third of the homes in Argentina's most populous province, a doctor said last week. The aedes aegypti mosquito appeared in Argentina in 1986 and is now being found in 36 percent of homes in Buenos Aires province, according to Dr. Alfredo Seijo of the Hospital Munoz. The province is home to 14 million people.

Malaria currently kills up to 2 million people each year and over 2 billion people are considered at risk of contracting the disease. Hot, humid periods in the 1990s have led to malaria cases being recorded in the United States in California, New Jersey, New York, Texas, Georgia, Florida, Michigan and Virginia, as well as in Toronto, Canada. Analyses show malaria outbreaks outside tropical regions becoming more common in the future.

Scientists and governments agree that the world has warmed by up to 0.6 degree Celsius (1.1 degree Fahrenheit) this century, according to WWF. The seven warmest years since scientists began keeping records almost 150 years ago have all occurred in the past decade with 1997 being the warmest. Every month from January to August in 1998 broke the previous record for that month.

If governments continue to allow anything like "business-as-usual" levels of global warming emissions, the build-up in the atmosphere is predicted to cause a further warming of 1 to 3.5 C (1.8 to 6.3 F) over the next century, according to WWF.

"Warmer winters and nights are altering the distribution of mosquito-borne diseases, while extreme weather events such as floods and droughts are spawning large "clusters" of infectious disease outbreaks. The costs of "business-as-usual" are mounting," said Epstein.

The problem will be worsened by global warming affecting the population balance of animal predators such as owls, snakes, birds and bats, animals that keep insects and rodents in check.

On top of the effects of the warming trend come more frequent and extreme weather events such as droughts, floods and storms which directly cause death and injury and open the door to other serious health problems, according to WWF.

During 1995 and the El Niño of 1997-98, which some scientists link to global warming, heat waves caused thousands of additional deaths in India and hundreds in central Europe and the United States.

At the same time, extreme droughts turned forests in Asia, the Mediterranean region, Mexico, Central America, Florida and California into tinderboxes. Enormous quantities of air pollution from burning forests led to a dramatic rise in the number of cases of eye irritation, respiratory illness and cardiovascular disease -- examples of the unexpected public health surprises which become more likely in a warming world.

Meanwhile, floods which affected Africa in late 1997 led to upsurges of cholera, malaria and Rift Valley fever. Cholera also affected parts of Latin America following flooding along the Pacific Coast and southern Brazil.

In developing countries, health conditions depend to a great extent on the success of the harvest. Both floods, which encourage the growth of fungi, and droughts, which promote whiteflies, locusts and rodents, have an impact on agricultural production. Half of the world's agricultural production, worth $250 billion, is currently lost to pests and weeds and this figure could increase with warmer and more unpredictable weather.

An ambitious multi-disciplinary study is under way to address the issue of climate change and public health, and its findings are being posted on a World Wide Web site set up by a Johns Hopkins University engineering graduate student. The study was made possible by a three-year, $3 million grant awarded to Hopkins last year by the Environmental Protection Agency. The EPA asked researchers to look at how climate change could affect public health and how policy makers should respond.

"One of the key purposes of the grant was to make this research public," says Rebecca Freeman, a 26-year-old doctoral student in the Department of Geography and Environmental Engineering. Data is developed at Hopkins and 11 other participating universities and government agencies. These partners include the University of Maryland, Penn State, Georgia Tech, the National Climate Data Center and the U.S. Department of Agriculture.

Copyright 1998, Environmental News Network, All Rights Reserved

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