Climate change is bound to affect the basic requirements for maintaining health - clean air and water, sufficient food, adequate shelter, and freedom from disease given the already high level of poverty, low nutritional levels and poor public health infrastructure in the country. (Dream 2047, Vigyan Prasar)
The question is, how will the changing climate affect our health? Climate influences many of the key determinants of health: it leads to extremes and violent weather events; resurgence of disease organisms and vectors; affects the quantity of air, food and water; and the stability of the ecosystems on which we depend. (CSE Draft Dossier: Health and Environment, Climate Change and Diseases: The Double Jeopardy)
Climate change can have both direct and indirect human health impacts. Indirect impacts arise from changes in temperature patterns, which may disturb natural ecosystems, change the ecology of infectious diseases, harm agriculture and fresh water supplies, exacerbate air pollution levels, and cause large-scale reorganization of plant and animal communities.
Extreme high air temperatures can kill directly. Heat waves directly contribute to deaths from cardiovascular and respiratory diseases, especially among the elderly people. Daily wage earners such as laborers and rickshaw pullers are at risk. Also persons living in informal structures may be more exposed to high temperatures
Warmer temperatures, shifting rainfall patterns and increasing humidity affect the transmission of diseases by vectors like mosquitoes. They are quite sensitive to changes in temperature and rainfall and are among the first organisms to extend their range when environmental conditions become favorable Thus, higher temperatures could influence the incidence of diseases such as malaria, dengue fever, yellow fever, and several types of encephalitis. Cold temperatures are often the limiting factor in mosquito survival, so any increase in minimum winter temperatures would likely extend mosquito ranges into temperate regions or higher altitudes where they do not survive.
Other vector-borne diseases such as Schistosomiasis, Chagas disease, Sleeping sickness, River blindness, and various strains of encephalitis all could change their ranges and patterns of infection in the course of climate change. Infectious diseases are emerging, resurging and undergoing redistribution on a global scale. Increase in temperature correlate with increased populations of some microorganisms that cause waterborne diseases, such as Vibrio cholerae bacterium, which causes Cholera. Higher ambient temperatures foster the growth of pathogens that thrive in or on food, such as Salmonella. (CSE Draft Dossier: Health and Environment, Climate Change and Diseases: The Double Jeopardy)
The increase of Chloro Fluoro Carbons in the atmosphere, leading to global warming will increase UV radiation in the atmosphere, affecting the immune systems and leading to infectious diseases. Susceptibility to important skin infections such as Leishmaniasis or Leprosy might be increased by greater exposure to UV light. The UV radiation affects the immune system of the skin and hence there might be an increased number of cases of skin cancer. Other minor effects are increased incidence of skin disorders, such as prickly heat and fungal skin disorders such as ringworm and athlete's foot as a result of increased temperature and humidity.
The phenomenon of rain is caused when heat from the Sun's rays on the surface of the seas, lakes and rivers induces evaporation. The water vapour formed in the process rises to a height where it condenses into moisture. If ambient conditions prevail it comes down as rain. But in the case of acid rain, water vapours reach the atmosphere, condense, and react with atmospheric gases like SO2 and NOx. When it rains, these atmospheric pollutants are deposited on the soil, vegetation, surface water or reservoirs. The deposition ultimately results in damage because of the acidity of the pollutants.
Acidic rainwater liberates mercury from the soil which can hinder brain development during the foetal stage. Fish-eating birds and humans acquire mercury by eating fish with high levels of the metal in them. The fish in turn ingest microorganisms, which consume mercury released by acid rain in the water. Acid rain also releases aluminum and cadmium. Cadmium can cause kidney disorders, besides accumulating in the outer layer of the kidney, causing wounds. Aluminum on the other hand, causes problems for kidney patients. In dialysis- the process of purifying the blood when the kidneys malfunction- it enters the blood stream directly without first having passed the body's normal protective barriers. This may cause skeletal and brain damage. It may also cause Alzheimer's and Parkinson's diseases. (Source: CSE Draft Dossier: Health and Environment, Climate Change and Diseases-The double Jeopardy)
| Mediating process | Health outcome |
| Direct | |
| Exposure to thermal extremes | Altered rates of heat- and cold-related illness and death |
| Altered frequency and/or intensity of other weather events | Deaths, injuries, psychological disasters; damage to public health infrastructure |
| Indirect | |
| Disturbances of ecological systems | |
| - Effects on range and activity of infective vectors and parasites | - Changes in geographic ranges and incidence of vector borne diseases |
| - Altered local ecology of water borne and food borne ineffective agents | - Changed incidence of diahorreal and other infectious diseases |
| - Altered food (especially crop) productivity, due to changes in climate, weather events, and associated pests and diseases | - Malnutrition and hunger, and consequent impairment of child growth and development |
| - Sea level rise with population displacement, and damage to infrastructure | - Increased risk of infectious diseases and psychological disorders |
| - Levels and biological impacts of air pollution, including pollen and spores | - Asthma and allergic disorders; other chronic respiratory disorders and deaths |
| - Social, economic and demographic dislocations due to effects on economy, infrastructure and resource supply | - Wide range of public health and nutritional impairment, infectious diseases, civil strife |
Source: Anon 1998, Environmental Change and Human Health, in World Resources 1998-99, p 68; cited in CSE Draft Dossier
(note: current or more recent data in this table could not be sourced)
Increasing traffic and exhaust as well as industrial emissions are raising concentrations of S02, NOx, O3 and suspended particulate matter, which are known to be damaging to human health. High temperatures raise the levels of ozone at ground level and other air pollutants, and hasten the onset of pollen season. Pollen and other allergens in the air trigger and aggravate asthma and cardiovascular respiratory diseases. (Dream 2047, Vigyan Prasar)
The impact of climate change on water availability is likely to be one of the most significant for the health of populations. Higher temperatures are hastening rates of evaporation of surface water thereby reducing the availability of fresh water. Lack of fresh water compromises hygiene and hence increasing incidence of diarrhoeal disease. On the other hand, too much water, in the form of floods, causes contamination of freshwater supplies. Extreme events like sea level rise coupled with stronger storm surges and coastal flooding can be followed by outbreak of diseases such as Cholera. (Dream 2047, Vigyan Prasar)
Inadequate drainage resulting in stagnant water is also a cause of mosquito-borne diseases such as malaria in urban areas. Flooding also may lead to the contamination of waters with chemicals, heavy metals or other hazardous substances, either from storage or from chemicals already in the environment (for example, pesticides).
Rising temperatures, changing patterns of rainfall, and more frequent droughts and floods are projected to decrease crop yields in many developing countries causing shortages of food supplies. This could result in severe malnutrition and under nutrition, especially among children, in countries where large populations depend rain-fed farming at subsistence level.
Perhaps the greatest long'term danger to human health from climate change will be the disruption of natural ecosystems, which provide an array of services that ultimately support human health. Biotic systems- whether in forests, rangelands, aquatic environments, or elsewhere- provide food, materials, and medicines; store and release fresh water; absorb and detoxify wastes; and satisfy human needs for recreation and wilderness. They are also intimately involved in sustaining the genetic basis of agriculture.
A potential health benefit of warmer global temperatures could be fewer cold-related deaths, as winters become milder. Yet, experts believe that the decrease in mortality will be negligible as compared to the increase in mortality resulting from global warming; studies indicate that higher mortality is generally associated with heat waves than cold spells (Source: CSE Draft Dossier: Health and Environment, Climate Change and Diseases-The double Jeopardy).
More assessments of the impacts of climate change on health in different tropical zones viz. plains, deserts, foothills, hilly and coastal areas are required. Assessments are also needed at the city level in order to inform decision making. The World Bank has made the following recommendations in this regard: (Source: Climate, climate change and human health in Asian cities, Sari Kovats and Rais Akhtar, Environment and Urbanization Magazine, 01 Apr 2008
- reliable and comprehensive assessments of risk vulnerabilities for exposed cities, and the dissemination of such information;
- establishment of early warning systems and evacuation plans, including emergency preparedness and neighborhood response systems;
- improved efficiency of the water supply management
- improving health educational and institutional capacity in urban environment management; and
- regularizing property rights for informal settlements and other measures to allow low-income groups to buy, rent or build good quality housing on safe sites.
Above all, protection of health from climate change has to be a part of a basic, preventive approach to public health.