World Health Day (WHD) on 7th April marks the foundation of the World Health Organisation (WHO) in 1948. This year, WHO has selected the theme “Protecting health from climate change” as it is posing an ever growing threat to global public health security.
According to the bulk of scientific opinion, the world is getting warmer. Most scientists are convinced that increasing concentrations of green warming house gases in the atmosphere are at least partly to blame for the global warming.
WHO estimated that climate change directly or indirectly contributes to about 77,000 deaths annually in Asia and the Pacific - about half of the world total attributed to climate change. Among the potential effects of global warming would be the appearance of mosquitoes where they were previously absent, with the accompanying threat of malaria and dengue fever. Some regions might be at risk of reduced rainfall, causing a shortage of fresh water and the resultant danger of water borne diseases. Millions of people could be at risk of malnutrition and hunger if arable land becomes unworkable. The increasing frequency of summer heat waves in temporate zones, e.g., Europe in 2003 and Asia in 2004 and typhoon, hurricanes and floods throughout the world are signs of changing weather and climate patterns.
In August 2003, Europe suffered its worst heat wave in recent memory. In France, temperature peaked at about 40oC. Unprepared for this kind of heat, many people – mostly the sick and elderly succumbed. In all, nearly 15,000 deaths in France that summer were attributed to the high temperatures; across Europe, the scorching weather may have claimed as many as 35,000 lives.
Developed countries share 15% of world population and 50% of carbondioxide emission. Temperature increase by 3-4o C would cause displacement of 330 million people due to floods, malaria infection for 220-400 million people due to flood, extinction of 20-30% of all the land species. Between 2000 and 2004, 262 million people were affected by natural calamities. Of these, 98% were in developing nations.
Issues for the Health Sector
Health hazards from climate change are diverse and global in nature. The hazards range from the risks of extreme weather events to changes in the dynamics of infectious diseases.
The health impact of climate change will be disproportionately greater in vulnerable populations which include the very young, elderly, medically infirm, poor and isolated populations. Climate-sensitive diseases such as diarrhoea, malaria and protein energy malnutrition already cause more than 3 million deaths globally. Even these numbers do not reflect the devastating indirect health impacts anticipated from the effect that climate change will have on food crops and the availability of fresh water in large areas of the world.
According to the most recent projects of the Intergovernmental Panel on Climate Change (IPCC), the global man temperature would increase by 1.4oC to 5.8oC between 1990 and 2100.
Climate Change and Human Health
Climate change is a significant and emerging threat to public health and changes the way we must look at protecting vulnerable populations. The IPCC confirmed that there is overwhelming evidence that humans are affecting the global climate and highlighted a wide range of implications for human health. Climate variability and changes cause death and disease through natural disasters, such as heat waves, floods and draughts. In addition, many important diseases are highly sensitive to changing temperatures and precipitation. These include common vector-borne diseases such as malaria and dengue; as well as other major killers such as malnutrition and diarrhoea.
The impacts of climate on human health will not be evenly distributed around the world. Developing country populations, particularly in small islands, states, arid and high mountain zones and densely populated coastal areas, are considered to be particularly vulnerable.
Heat Waves and Cold Snaps
Perhaps the most obvious impact of global warming will be the direct effect - a warmer planet will experience more extreme heat waves. It is difficult to predict the future effect on mortality levels, because as heat waves become more frequent, we can expect societies to adjust – technologically, behaviourally and physiologically. Technological adaptations such as the installation of collective air conditioners and the construction of heat-minimizing houses will happen more quickly among the rich, so heat waves are likely to have a disproportionate effect in less-developed countries and in the poorer segments of rich countries.
Northern countries with severe winters have a high mortality rate in winter because more sick and elderly people succumb in cold weather and because blizzards and extreme cold create dangerous conditions in which accidental deaths are more likely.
Extreme Events and Disasters
Some of the health effects of weather related disasters, in addition to the immediate death and injury to people and damage to property, include : increase in psychological stress, depression and feelings of isolation amongst people affected by natural disasters; decrease in nutrition due to poor agricultural yields, caused for example, by prolonged draught problems and food distribution; increase in disease transmission due to a breakdown in sewerage and garbage services. For example, cholera is one disease that thrives in such situations, particularly when flooding causes the contamination of drinking water by sewerage systems.
Apart from the ecological and agricultural impacts, the availability of water may be reduced, with implications for human health. More frequent draught conditions would increase the risk of bush fires, which can kill people, release large quantities of particulate matter that can cause respiratory problems and degrade water catchments.
Many infectious diseases are dependent on vector organisms, which are sensitive to environmental factors and therefore will be affected by global warming. Biological modeling under various climate scenarios suggested a widening of the potential transmission zone of some disease causing pathogens and their vectors, such as mosquitoes.
Food and water borne diseases are also susceptible to climate change. Food-poisoning bacteria grow best when the ambient temperature is in the range of 35-37oC. Scientists speculate that if temperatures rise under global warming, the incidence of diseases caused by food-poisoning and by the contamination of drinking and swimming water could increase dramatically.
Rising Sea Levels
Scientists predict that sea levels will rise as the global temperature rises, due to the melting of land-based ice in the polar regions and glaciers and the thermal expansion of the oceans. According to the most recent projects, sea levels would rise between 9 and 88 cms by the year 2100. A rise of this magnitude would have disastrous consequences for people living on low-lying islands, such as the Maldives group in the Indian ocean and many South-Pacific Islands. Higher sea level leads to coastal flooding and an increase in frequency of extreme high water levels from storm surges. Related problems are the contamination of coastal fresh water supplies with encroaching sea water and the degradation of fishing and agricultural areas.
Warmer, the Sicker
Considerable uncertainty remains about how the climate may change and how such changes might affect human health. It seems likely, however, that people living in tropical and sub-tropical areas will be most affected. Affluent countries and soial groups will best adapt to climate change by reducing the impacts of natural disasters such as flooding, fire and draught, by maintaining high quality health and emergency infrastructures and by installing technologies that help ward off the worst climatic affects.
Developed countries should cut their carbon emissions at least by 80% by the year 2050, with 20-30% cuts by 2030, if the earth is to be saved from a complete environmental catastrophe, says the Human Development Report (HDR) 2007. The report also calls for 20% cuts in carbon emissions by fast growing economies like India and China. The cost of this process would be only 1.6% of Global GDP.
Through increased collaboration, the global community will be better prepared to cope with climate – related health challenges world wide. A few examples of such collaborative actions are: strengthening surveillance and control of infectious diseases, ensuring safer use of diminishing water supplies and coordinating health action in emergencies.
The health impacts of climate change will be difficult to reverse in a few years or decades. Yet, these possible impacts can be avoided or controlled. For example, controlling vectors, reducing pollution from transport and efficient land use and water management are tested measures that can help.
The risk to human and ecological well-being is too great and prevention will be far better and easier than cure.
by - A.N. Khan (Former Assistant Director, National Environmental Engineering Research Institute, Nagpur & Technical)