Climate change refers to any significant change in measures of climate. Potential effects of this climate change are likely to include more variable weather, stronger and longer heat waves, more frequent heavy precipitation events, more frequent and severe droughts, extreme weather events such as flooding and tropical cyclones, rises in sea level, and increased air pollution. Other effects may result from ecosystem shifting and disruption.
Climate change is an emerging risk factor for human health. According to Third Assessment Report, the IPCC summarized to state: “Climate change can affect human health directly (e.g., impacts of thermal stress, death/injury in floods and storms) and indirectly through changes in the ranges of disease vectors, water-borne pathogens, water quality, air quality, and food availability and quality. The actual health impacts will be strongly influenced by local environmental conditions and socio-economic circumstances, and by the range of social, institutional, technological, and behavioral adaptations taken to reduce the full range of threats to health.”
Broadly, a change in climatic conditions can have three kinds of health impacts:
· Those that are relatively direct, usually caused by weather extremes.
· The health consequences of various processes of environmental change and ecological disruption that occur in response to climate change.
· The diverse health consequences – traumatic, infectious, nutritional, psychological and other – that occur in demoralized and displaced populations in the wake of climate-induced economic dislocation, environmental decline, and conflict situations.
Climatic changes over recent decades have probably already affected some health outcomes. Indeed, the World Health Organization estimated, in its "World Health Report 2002", that climate change was estimated to be responsible in 2000 for approximately 2.4% of worldwide diarrhoea, and 6% of malaria in some middle-income countries.
Marked short-term fluctuations in weather can cause acute adverse health effects:
· Extremes of both heat and cold can cause potentially fatal illnesses, e.g. heat stress or hypothermia, as well as increasing death rates from heart and respiratory diseases.
· In cities, stagnant weather conditions can trap both warm air and air pollutants -- leading to smog episodes with significant health impacts.
· These effects can be significant. Abnormally high temperatures in Europe in the summer of 2003 were associated with at least 27,000 more deaths than the equivalent period in previous years.
Other weather extremes, such as heavy rains, floods, and hurricanes, also have severe impacts on health. Approximately 600,000 deaths occurred world-wide as a result of weather-related natural disasters in the 1990s; and some 95% of these were in poor countries.
To large extent, a changing climate is likely to affect public health which depends on safe drinking water, sufficient food, secure shelter, and good social conditions. Reviews of the likely impacts of climate change by the IPCC suggest that a warming climate is likely to bring some localized benefits but overall, however, the health effects of a rapidly changing climate are likely to be overwhelmingly negative, particularly in the poorest communities, which have contributed least to greenhouse gas emissions. Some of the health effects include:
· Increasing frequencies of heat waves: recent analyses show that human-induced climate change significantly increased the likelihood of the European summer heat wave of 2003.
· More variable precipitation patterns are likely to compromise the supply of freshwater, increasing risks of water-borne disease.
· Rising temperatures and variable precipitation are likely to decrease the production of staple foods in many of the poorest regions, increasing risks of malnutrition.
· Rising sea levels increase the risk of coastal flooding, and may necessitate population displacement. More than half of the world's population now lives within 60km of the sea. Some of the most vulnerable regions are the Nile delta in Egypt, the Ganges-Brahmaputra delta in Bangladesh, and many small islands, such as the Maldives.
· Changes in climate are likely to lengthen the transmission seasons of important vector-borne diseases, and to alter their geographic range, potentially bringing them to regions which lack either population immunity or a strong public health infrastructure.
Heat exposure has a range of health effects, from mild heat rashes to deadly heat stroke. Heat exposure can also worsen several chronic diseases, including cardiovascular and respiratory disease. The results can be severe and result in both increased illness and death. Heat also increases ground-level ozone concentrations, causing direct lung injury and increasing the severity of respiratory diseases such as asthma and chronic obstructive pulmonary disease.
The direct effects of extreme weather events include drowning from floods, injuries from floods, and structural collapse. Indirect effects outnumber the direct effects and likely will be more costly. Potential indirect effects include aggravation of chronic diseases due to interruptions in health care service, significant mental health concerns both from interrupted care and geographic displacement, and socioeconomic disruption resulting from population displacement and infrastructure loss.
Many of unanticipated ecosystem effects could have indirect health effects. Increased concentrations of ground-level carbon dioxide and longer growing seasons could result in higher pollen production, worsening allergic and respiratory disease. Increased carbon dioxide concentrations in sea water may cause oceans to grow more acidic and is likely to contribute to adverse ecosystem changes in the world’s tropical oceans. This would have potentially dramatic implications for fisheries and the food supply in certain regions of the world. Major regional ecosystem stresses may result in mass population movement and conflict, with significant health effects.
Air quality is highly affected by weather and climate conditions. In turn, certain aspects of air quality are known to affect health. Ozone causes direct, reversible lung injury; increases premature mortality; worsens respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD); and may cause chronic lung damage.
Storms and extreme precipitation events have several direct health effects. They are associated with flooding, which can immediately cause injury and death, followed by a spike in traumatic injury and carbon monoxide poisoning during redevelopment and rebuilding efforts when the events are severe enough to prompt evacuation and resettlement. Storms resulting in evacuation are also associated with increased risk for gastrointestinal illness among evacuees. Extreme precipitation events are also associated with outbreaks of gastrointestinal disease. Heat waves are already the most deadly weather-related exposure in the U.S. Studies suggest that, if current emissions hold steady, excess heat-related deaths in the U.S. could go up from an average of about 700 each year currently, to between 3,000 and 5,000 per year by 2050.
Climate is one of many variables known to affect the rates of vector-borne and zoonotic diseases. Of particular importance are vector mosquito species, which spread malaria and viral diseases such as dengue and yellow fever. Malaria, today, is mostly confined to tropical and subtropical regions. The disease’s sensitivity to climate is illustrated by desert and highland border areas where higher temperatures and rainfall associated with El Niño may increase transmission of malaria. Dengue is the most important arboviral disease of humans particularly in urban settings. Between 1970 and 1995, the annual number of dengue epidemics in the South Pacific was positively correlated with La Niña conditions (i.e., warmer and wetter). In the tropics diarrhoeal diseases typically peak during the rainy season. Both floods and droughts increase the risk of diarrhoeal diseases. Major causes of diarrhoea linked to heavy rainfall and contaminated water supplies are: cholera, cryptosporidium, E.coliinfection, giardia, shigella, typhoid, and viruses such as hepatitis A.
Various analyses have shown that health impacts are often the largest single contributor to the costs of environmental damages. The Govt. health authorities should undertake a comprehensive evaluation of the possible health implications of such changes and need to determine priorities for planning and decision-making. The health sector should be involved jointly with agricultural, meteorological, environmental, and planning agencies to ensure that health considerations are given adequate weight.
But not only for these, individual awareness is also needed such as lifestyle change, behavioral change, efficient use of energy etc.
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