Today October 15th is the Blog Action Day and this year's theme is climate change.
What are the effects of climate change on health?
Rapidly changing Climate is a major challenge to public health together with poverty, inequity, and infectious and non-communicable diseases. Furthermore, the poorest countries will suffer the greatest consequences of climate change even though they contributed the least for emissions.
Patterns of disease and mortality
Global temperature rise will directly affect health. The heat waves of 2003 in Europe caused up to 70 000 deaths, especially from respiratory and cardiovascular causes. Rising temperatures are likely to generate heat-related stress, increasing the short-term mortality rate due to heatstroke. Regions that are heavily urbanised will be more adversely affected than rural ones.
Rising temperatures will also affect the spread and transmission rates of vector-borne and rodent-borne diseases. Temperature affects rate of pathogen maturation and replication within mosquitoes, the density of insects in a particular area, and increases the likelihood of infection. Therefore, some populations who have little or no immunity to new infections might be at increased risk. Vector reproduction, parasite development cycle, and bite frequency generally rise with temperature; therefore, malaria, tick-borne encephalitis, and dengue fever will become increasingly widespread. In some cases, extreme events, such as heavy rains, will wash away eggs and larvae and decrease vector populations.
Mosquitoes responsible for malaria will grow, by accessing warm high altitudes, in places once free of the disease. It is estimated that 260—320 million more people will be affected by malaria by 2080 as a consequence of new transmission zones.
Dengue fever is sensitive to climate. The disease is prominent in urban areas because of inadequate water storage that affects about 100 million people worldwide. Climate change will increase the number of regions affected by arbovirus, such as Australia and New Zealand. Heavy rainfall and a rise in temperature increase the rate of infection. By 2080, about 6 billion people will be at risk of contracting dengue fever as a consequence of climate change, compared with 3·5 billion people if the climate remained unchanged.
Schistosomiasis, fascioliasis, alveolar echinococcosis, leishmaniasis, Lyme borreliosis, tick-borne encephalitis, and hantavirus infections are all projected to increase as a result of global climate change.
As ocean temperatures rise with global warming and more intense El Niños, cholera outbreaks might increase as a result of more plankton blooms providing nutrients for Vibrio cholerae. In 1998, increased rainfall and flooding after hurricane Mitch in Nicaragua, Honduras, and Guatemala caused a leptospirosis outbreak, and an increased number of cases of malaria, dengue fever, and cholera.
Climate change threatens human health through its effect on under nutrition and food insecurity. Chronic and acute child malnutrition, low birth weights, and sub optimal breastfeeding are estimated to cause the deaths of 3·5 million mothers and young children every year. Furthermore, one in three children under the age of 5 years born in developing countries suffer from stunting due to chronic under nutrition. Climate change will compound existing food insecurity.
A study suggests that half of the world's population could face severe food shortages by the end of the century because rising temperatures take their toll on farmers' crops. Harvests of staple food crops, such as rice and maize, could fall between 20% and 40% as a result of increased temperatures during the growing season in tropical and subtropical regions.
Water and Sanitation
Safe and reliable access to clean water and good sanitary conditions are essential for good health. In 2002, 21% of people living in developing countries did not have sustained access to an improved water source, and 51% did not have access to improved sanitation.
Changing rainfall and temperature over the next decades are likely to make provision of clean water, good sanitation, and drainage even more complicated than it is now. Average annual rainfall is forecast to decrease in some regions and increase in others, and droughts and floods are likely to become more frequent and intense. Regional temporal patterns of rainfall might also be altered: the problem is not simply sustained drought, but also severe rainfall all at once followed by less rainfall, thus annual rainfall might rise, but still cause drought.
More than a sixth of the world's population currently live in glacial-fed water catchments, which are vulnerable to climate change. Increasing rates of glacial melting are predicted to lead to great reductions of water availability. In the near future, high peak flows in glacial-fed rivers are expected, as the rate of glacier-mass loss increases, followed by dramatic reductions in river flow and freshwater availability as glaciers progressively disappear. Rising temperatures are also likely to result in earlier snow thawing and increased rain relative to snow precipitation, bringing peak river flows earlier in the year, potentially exacerbating dry season water scarcity.
Reduced river flows and increased water temperature will lead to declining water quality as the dilution of contaminants is reduced, less oxygen is dissolved in water, and microbiological activity increases. These effects could lead to major health problems for vulnerable people, especially during drought, and might increase the risk of conflict and major population migration.
Many of the most serious public health consequences of climate change will be experienced by the world's poorest nations, increasing global health inequities. Basic infrastructure for much of the world's population is inadequate to meet essential health care needs, and our ability to cope effectively with the aftermath of natural disasters is insufficient. Overall, all the underlying social, economic, and ecological determinants of global illness and premature death will be exacerbated by climate change. Progress towards the Millennium Development Goals and achievement of the 2015 targets might be impaired or reversed. Because climate change acts mostly as an amplifier of existing risks to health, poor and disadvantaged people will experience greater increments in disease burden than rich, less vulnerable populations.
Gender inequity is another important factor. In developing countries, women are among the most vulnerable to climate change; they not only account for a large proportion of the agricultural workforce but also have few alternative income opportunities. Women manage households and care for family members, which limit their mobility and increase their vulnerability to natural disasters and other local sudden climate changes. Efforts to keep the adverse effects of climate change to a minimum should ensure that policies address issues of women's empowerment.
Climate change is not just an environmental issue but also a health issue. The ability to adapt to the health effects of climate change depends on measures that reduce its severity—i.e., mitigation measures that will drastically reduce carbon emissions in the short term, but also increasing the planet's capacity to absorb carbon. This is a crucial issue that must be acted upon urgently.
Source: The report of The Lancet Commission on health effects of climate change published in The Lancet dated 16th May 2009.