Impacts of climate Change on health

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Impacts of climate Change on health

PEOPLE have adapted to living in a wide variety of climates around the world from the tropics to the arctic, both climate and weather have a powerful impact on human life and health. 
The extremes of weather (heavy rains, floods, and hurricanes) occur over a short period of time (a few days) and can severely affect health. Poorer communities are much more vulnerable to the health impact of climate variability than rich ones of approximately 80,000 deaths which occur worldwide each year as a result of natural disasters about 95% of them are in poor countries. In weather-triggered disasters people and animals die; homes, crops and resources are destroyed; public health infrastructure (e.g. hospitals, roads) is damaged. Some recent examples:

  • In 1998, hurricane Mitch caused over 7,500 deaths in Honduras, Nicaragua, Guatemala and El Salvador. Half the population was evacuated from their homes and, in Honduras, 75% were left without clean water. Sewage networks and water supplies were disrupted, bringing increases in the incidence of cholera and other diarrhea type diseases;
  • In 1998, China experienced its worst situation. Thousands of people have been lost their lives and millions of houses were totally destroyed.
  • In 1999, a cyclone in Orissa, India, caused of 10,000 deaths. The total number of people affected was estimated at 10-15 million;
  • In 2000, floods in Mozambique killed 500 people and left 330,000 homeless.

Human physiology can handle most variation in weather within certain limits. But marked short-term fluctuations in weather can cause acute adverse health effects, leading to a greater number of hospital admissions and even to increased death rate:
Heat waves can cause heat related illness and death (e.g. heat stroke). The elderly and persons with heart or respiratory disease are particularly vulnerable;  

Heat weaves in India in 1998 were associated with many deaths. In Chicago, USA, more than 500 deaths were caused by a heat wave in July 1995;
In cities, stagnant weather conditions can trap both warm air and air pollutants-leading to smog episodes which have significant impact on health;
Climate plays an important role in vector-borne diseases-a major cause of illness and death in tropical countries- transmitted by insects such as mosquitoes, ticks, sand flies and tsetse flies. These cold-blooded vectors are sensitive to direct effects of climate such as temperature, rainfall patterns and wind. Climate also affects their distribution and abundance through its effects on host plants and animals.

Malaria transmission is particularly sensitive to weather and climate. Unusual weather conditions, for example, a heavy downpour, can greatly increase the mosquito population and trigger an epidemic. This is what happened in the Wajir district of Kenya in 1998. Under normal weather conditions this region is too dry for the vectors and very little transmission occurs. There had not been a malaria epidemic since 1952 and the local health sector was unprepared for the major outbreak that followed the heavy rains. On the desert and highland fringes of malaria areas, malaria transmission is unstable and the population lacks protective immunity. Thus, when weather conditions (rainfall and temperature) favor transmission, serious epidemics may occur. In some countries, such as India, Colombia and Venezuela, fluctuations in malaria risk over the years have been linked to changes in rainfall associated with the El Nino cycle.

Global warming: About two thirds of solar energy reaching on the earth. Earth is absorbed by the earth surface which consequently gets warmer. The heat radiates back to the atmosphere, where some of it is trapped by ‘green house gases, mostly carbon dioxide.
The average surface temperature is about 15°C-about 33°C higher than it would be in the absence of the greenhouse effect; without such gases most of the Earth’s surface would be frozen with a mean air temperature of -18° C.

Human activities have polluted the atmosphere to the extent of being able to affect the climate. The atmospheric concentration of carbon dioxide has increased by 31% since preindustrial times, causing more heat to be trapped in the lower atmosphere. Emissions of carbon dioxide are still increasing. Many countries are working to reduce greenhouse gas emissions under the United Nations Framework Convent ion on Climate Change. Unfortunately, current international agreements are not sufficient to prevent the world facing significant changes in climate and a rise in sea levels.

The scientific evidence for climate change and its impacts is assessed by the Intergovernmental Panel on Climate Change (IPCC). Assessment Report (2001), “there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities”. Some impacts include:

  • The average temperature in many regions has been increasing in recent decades. The global average surface temperature has increased by 0.20 –60 C over the last century;
  • Globally, 1998 was the warmest year and the 1990s was the warmest decade on record.
  • Many areas has experienced increases in rainfall, particularly mid to high latitude countries;
  • In some regions, such as parts of Asia and Africa, the frequency and intensity of droughts have been observed to increase in recent decades;
  • Episodes of El Nino have been more frequent, persistent and intense since mid-1970s compared with the previous 100 years.
  • Projections of future climate change are derived from series of experiments with global mate models which, in turn, rely on estimates of future population growth and energy use. Climatologists of the IPCC have reviewed the results of these experiments in order to estimate changes in climate in the course of this century. They predict:
  • Global mean surface temperature will rise by 1.40 – 5.80 Warming will be greatest over land areas, and at high latitudes;
    • The projected rate warming is greater than anything humans have experienced in the last 10,000 years;
    • The frequency of weather extremes is likely to change leading to an increased risk floods and drought. There will be fewer cold spells but more heat waves;
  • The frequency and intensity of EL Nino may be affected;
  • Global mean sea level is projected to rise by 9-88 cm by the year 2100. More than half of the world’s population now lives within 60KM of the sea and some of the most vulnerable regions are the Nile delta in Egypt, the Ganges-Brahmaputra delta in Bangladesh, and many small islands including the Marshal Islands and the Maldives.

Human societies are very vulnerable to climate extremes (droughts, floods, wind storms). A changing climate would entail changes in the frequency and/or intensity of such extremes. This is a major concern for human health. To a large extent, public health depends on safe drinking water, sufficient food, secure shelter, and good social conditions. All these factors can be affected by climate change:

  • Fresh water supplies may be affected, reducing the availability of clean water for drinking and washing. Supplies can be contaminated and sewage systems may be damaged increasing the risk of spread of infectious diseases such as diarrhea like diseases;
  • Food production may be undermined in vulnerable regions, not only directly but also indirectly through pests and plant or animal diseases. Local declines in food production would lead to hunger and malnutrition with long-term health consequences, especially for children;

Food and water shortages may lead to conflicts in vulnerable regions, with serious implications for public health;
*          These and other climate related impacts on human health and well-being may lead to population displacement, creating environmental refugees and consequently further health implications.

  • Changes in climate may alter the distribution of important vector species (e.g. mosquitoes) and may increase the spread of disease to new areas which lack a strong public health infrastructure.

*          Highland populations (such as in East Africa or Papua New Guinea) that fall outside areas of stable endemic malaria transmission may be particularly vulnerable to increases in malaria due to climate warming.

  • It is unlikely that malaria would be reintroduced into developed countries (such as Western Europe or the United States of America) because these countries have well- developed public health infra structure. However, the risk of localized outbreaks may increase.
  • The seasonal transmission and distribution of many other diseases transmitted by mosquitoes (dengue, yellow fever) and by ticks (Lyme disease, tick-borne encephalitis) may also be affected by climate change.
    A report by a WHO Task Group has warned that climate change may have an important impact on human health. Not only will climate change exacerbate various current health problems, it may also bring new and unexpected ones.

Response strategies aimed at lessening potential health impact of the anticipated climate changes should include:
Monitoring of infectious diseases and disease vectors to detect early changes in incidence or geographical distribution;
• Environmental management;
• Disaster preparedness;

  • Improved early warning systems and epidemic preparedness;
    • Improved water and air pollution control;
    • Public education directed at personal behavior;
    • Training of researchers and health professionals.
    WHO’s Response: As a response to the requirements stated in Agenda 21 and in the United Nations Framework Convention on Climate Change, a number of organizations is carrying out significant climate-related activities.

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