Everybody’s health will be affected by climate change, predicts Diarmid Campbell-Lendrum of the World Health Organization, as diseases, extreme weather, and food and water shortages impact all populations.
 | Life SaverA baby receives treatment for malnutrition in Ethiopia in May 2008. The failure of seasonal rains and high food prices meant millions of Ethiopians required emergency food aid (Photo: Reuters) |
Does climate change directly impact on human health and disease?
We have very strong evidence that climate changes have an effect on human health. You can see the impacts of extreme weather events like the droughts in the Horn of Africa in the 1980s, El Nino events, or the 2003 heat wave across Europe.
Weather related natural disasters attract the most attention because they kill large amounts of people, about 60,000 a year. They are definitely important, but we are more concerned about the climate change effects on what are already huge disease burdens.
Today, 3.5 million people die every year from the consequences of malnutrition, 2.2 million from diarrheal diseases and just under 1 million from malaria. Climate change is likely to make it worse.
The 2002 World Health Organization study, The Global Burden of Disease from Climate Change, estimated that climate change was causing over 150,000 additional deaths every year, mainly through increases in malaria, diarrhea and the consequences of malnutrition.
How are these illnesses affected by climate change?
In developing countries with poor sanitation increasing temperatures are associated with diarrheal diseases—caused by bacteria that replicate faster at higher temperatures. A study from Lima, Peru showed a clear correlation between daily temperatures and numbers of children with diarrheal diseases.
There is also strong evidence for a link with extreme precipitation or drought. Flooding tends to overload sanitation services, while in times of drought people store freshwater for longer making it harder to maintain hygiene.
Mosquitoes and the malaria parasite are both highly sensitive to temperature: mosquitoes bite more often at higher temperatures but more importantly increasing temperatures speed up the development of the malarial parasite inside the mosquito.
In highland areas in East Africa rising temperatures could make it easier to transmit malaria at higher altitudes, where there are high population densities.
Mosquitoes breed in water so increased precipitation will increase areas vulnerable to malaria whereas drought will probably reduce malaria transmission, for example in the Sahel region where there has been expanding desertification, although that presents other problems.
Problems such as lack of food and water?
Malnutrition may be the largest concern of all; it is probably the single largest contributor to ill health globally, making people increasingly vulnerable to other diseases.
The Intergovernmental Panel on Climate Change (IPCC) predicts decreased food production for developing countries close to the equator. Here, even a small decrease in nutrition rates has a very large impact because it is such a huge problem already. The malnutrition burden will be the largest burden from climate change.
Those most vulnerable to these three main illnesses over the next few decades will be those in poorer countries not protected from climate hazards now. Then there are longer-term implications of climate change that are difficult to quantify but are even more concerning.
 | Access to SanitationPercentage of population with access to adequate sanitation - a public sewer, septic system, or improved-pit or pour-flush latrine (Graphic: Allianz) |
What are these long-term threats?
Things like increased water stress in places like the Middle East and North Africa due to less rainfall and higher rates of evaporation and the retreat and disappearance of glaciers. We know that predictable summer melting of glaciers provides water to about one sixth of the world population.
It is very difficult to maintain health when the taps go off. It is not something you can treat with a bed net or a pill, and it is not clear how we can adapt our way out of this. It’s the same issue with sea level rises and increased numbers of storms in low-lying countries like Bangladesh.
Then there is effect of climate change on biodiversity and species extinction. All human life depends on ecosystem services such as pollination of plants and fisheries, but these services are likely to be at risk if significant numbers of species die off.
Will air pollution increase with climate change and what are the likely health impacts?
There is evidence some air pollutants like ground level ozone from fossil fuel consumption will get worse. Globally about 800,000 premature deaths are associated with bad air quality.
Societies are thinking about reducing greenhouse gases by reducing fossil fuel consumption, which would reduce air pollution and improve health. The important thing is that these health benefits would in many cases repay the costs of mitigation policies.
For example, facilitating public transport and cycling or walking to work not only reduces greenhouse gases and air pollution but also makes it easier to exercise and tackle obesity and physical inactivity, two of the most rapidly growing health problems worldwide.
These measures ought to be attractive to policymakers because they can show that reducing greenhouse gases can bring direct, immediate health benefits.
What are the best ways to protect people against infectious diseases spread by climate change?
For malaria and diarrheal diseases we do have effective interventions: providing clean water and sanitation services, cheap salt and sugar oral re-hydration treatments, education about hygiene, mosquito bed nets, indoor spraying of insecticide, and drug treatment.
With increased efforts we could cope with diarrhea and malaria irrespective of climate change. Malaria has been rolled back from Europe and rates are decreasing in Brazil, India and China as living standards increase and well designed control programs are implemented.
One problem is developing countries are naming health as a priority when they apply to the Global Adaptation Fund and other bodies for financial assistance, but when they submit projects for funding there is a low proportion of health projects. We would like to see greater involvement by the health sector in those planning processes.
We need to accelerate progress towards the Millennium Development Goals—which will significantly affect the health of populations—before climate change takes too much of a grip.
editor: James Tulloch
publishing date: February 24, 2009
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