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FEATURE: Global warming: its effect on health
Global warming and the climatic instability that accompanies it tends to affect our health seriously. There are strong indications that a disturbing change in disease patterns has begun and that global warming is contributing to these changes. The year 1997 was the warmest on record and every month from January through August in 1998 broke the previous world heat record for that month. Although accurate temperature records extend back only a little more than a hundred years, tree rings, ice core samples and fossil pollen records indicate that the 1990s have been the hottest decade in over 600 years.
Scientists agree that there is a significant warming trend and they are concerned by its rate. They agree that this warming is partially caused by the emission of greenhouse gases in the atmosphere, specially carbon dioxide. Most carbon dioxide pollution is the result of burning of fossil fuel, such as coal and oil, to produce electricity or used as fuel in automobiles. Scientists have determined that in many parts of the world extreme weather conditions such as drought, floods and storms are becoming more frequent and severe. These extreme weather conditions directly threaten human health and often act as a catalyst to outbreaks of infectious diseases.
Emerging infectious diseases
Infectious diseases are emerging on a global scale. According to a World Health Organization (WHO) report, at least 30 diseases new to medical science have emerged in the past 20 years. Environmental change including global warming apparently contributes to this global resurgence of diseases and may do so to an even greater extent in the future. Contagious diseases, like diphtheria and whopping cough, have resurged in many countries. Diseases which are spread through insects and animals, such as mosquitoes and mice as vectors (carriers), respond most readily to environmental change. Some diseases transmitted from person-to-person like meningitis are also associated with environmental conditions. In 1996 over 100,000 people contracted meningitis in West Africa, during periods of severe drought.
Ecological impacts: predators and prey
Climate plays an important role in maintaining the balance among predators and their prey and the ratio of these “functional groups” of species as natural biological controls over pests and pathogens (infectious disease agents). For example, owls and snakes help regulate the population of rodents involved in the transmission of lyme disease and plague. Similarly freshwater fish, reptiles, birds and bats limit the abundance of mosquitoes, some of which carry germs of diseases such as malaria and dengue fever, yellow fever and encephalitis.
Reduction and fragmentation of natural habitat worldwide is reducing predator population. Excessive reliance on pesticides kill “friendly” insects and predators. Global warming and increased climatic variability also disrupt biological systems that have evolved over the millennia, and which control the population of pestilent organisms.
Warming and disease
In a warm world, the rate of insect biting and microorganism maturation increases. Warming can also increase the number of insects, provided that moisture is adequate although excessive heat can decrease the survival of microorganisms and their host. Between extreme heat and cold is an optimum range of temperature in which warmth enhances our metabolism and chances for disease transmission. The nighttime warming and the early occurrence of spring in the Northern Hemisphere also enhances insect survival.
El Nino and health
The effects of El Nino in 1997/98 was the strongest of the century and its impact was felt worldwide. Extreme droughts and fires occurred in Asia, across the Mediterranean nations, the Amazon, Mexico’s tropical rain forests and in some regions of North America.
The incidence of eye irritation respiratory illnesses and cardiovascular diseases rose dramatically in many of these regions. Heat waves killed thousands in India and hundreds in central Europe and the United States. Devastating floods occurred in China and Bangladesh as El Nino waned.
The El Nino/Southern Oscillation phenomenon is a natural climatic cycle. But heat absorption by the world’s oceans as a result of global warming alter the natural rhythm of El Nino, causing it to recur more frequently and with greater ferocity. El Nino brought about changes in the ocean currents and winds in the eastern pacific which altered the jet stream as a result of which intense droughts and heat waves were experienced. At the end of an El Nino, the next phase of the cycle, La Nina often takes over and the opposite pattern occurs.
Health in marine ecosystems
Coastal pollution, ocean warming and flood promote the proliferation of toxic “red tides” and encourage diseases, such as cholera. “Browntides” affecting seaweeds and shellfish. Pollution and warming also spread diseases of the coral reefs and seaweed beds. Marine life highly depends on these habitats.
Air pollution and global warming
Global warming is not an isolated phenomenon. It is associated with existing environmental problems, such as acid rain and air pollution. It also takes place when fossil fuel such as coal and oil is burned. The aggregate impact of air pollution and climatic change increases respiratory diseases such as asthma and bronchitis.
These additive effects can occur in a number of ways:
* Greater heat and humidity enhance the conversion of nitrogen oxides to photo chemical smog. These allergens are transmitted through the air.
* Warmer winters and earlier spring increases pollen production.
* Heat waves and air pollution increase the local concentrations of the pollutants.
* Forest fires from droughts lead to an increase in respiratory and cardiovascular diseases, due to smoke and chemical inhalation.
Conclusion
Our health depends upon development. The question thus arises is not whether to develop, but how to develop with clean energy sources, while stimulating global, equitable economic growth.
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