Select Committee on International Development Minutes of Evidence

Memorandum submitted by the London School of Hygiene and Tropical Medicine


1.  The potential impacts of climate change on human health

  Global climate change will probably have a wide range of health impacts as many diseases are sensitive to climate. The IPCC Third Assessment Report[15] currently identifies the following main mechanisms by which climate change will affect human health.

    —  Changes in distribution and seasonal transmission of malaria and other diseases that are transmitted by insects and ticks (eg dengue, mosquito-borne viruses, leishmaniasis). Vector-borne diseases are one of the major contributors to the global burden of disease (according to the WHO) and are highly sensitive to climate conditions.

    —  Changes in food supply due to reduced crop yields in vulnerable areas.

    —  Changes in frequency and or intensity of weather disasters, particularly floods (coastal and riverine) and droughts.

    —  Increases in food and/or water borne diseases, particularly diarrhoeal diseases, as higher temperatures encourage the growth of micro-organisms and more erratic rainfall increases the frequency of contamination of surface water.

    —  Population displacement and economic disruption associated with climate change and sea level rise.

    —  The direct effects of higher temperatures in urban populations, causing increased cardio- respiratory mortality in relation to heatwaves. In temperate cities, increases in heat related deaths may be more than offset by decreases in cold-related deaths but in tropical cities the net effect is likely to be adverse.

  The IPCC concluded that the negative impacts on health will be greater than the benefits to health of climate change and that the worst impacts will be in developing countries.

  The World Health Organisation has included climate change as one of the six environmental risk factors in the forthcoming Global Burden of Disease assessment. Climate change research has focused on the physical, chemical and biological impacts, and impacts within economic sectors such as agriculture and water resource management. Health research has been directed towards better understanding of direct temperature effects on health, of the seasonality of certain infectious diseases, and of the public health consequences of extreme weather events. Predictive models have been developed that link climate scenarios with vector-borne disease distributions. Policy-makers should appreciate that, while our scientific capacity to model various health outcomes of climate change continues to evolve, it is not possible to make precise and localised projections for many health outcomes, especially for those that result indirectly from a sequence of impacts.

  Reduced food and water supplies. Climate change represents an additional pressure on the world food supply system. The current IPCC assessment is that yields of cereal grains would increase at high and mid-latitudes, but decrease at lower latitudes. The world's food system may be able to accommodate such regional variations at the global level. However, at the local level, some populations may be severely affected. The UN Food and Agriculture Organization (FAO, 1999) estimates that 790 million people in developing countries do not have enough to eat. Environmental factors, both natural and those that are a consequence of human activities, can limit agricultural potential. Adaptation should be undertaken, via development of crop breeding and management programmes for heat and drought conditions. In the near term, adaptation strategies will improve productivity in marginal environments.

  Diarrhoea is one of the most important causes of death and morbidity, particularly of children, in developing countries. Recent studies have demonstrated it is highly sensitive to relatively small increases in temperature: for example, research in Peru[16] showed that each 1ºC increase in daily temperature resulted in an 8 per cent increase in paediatric admissions for diarrhoea. This suggests that predicted temperature increases over the coming century are likely to significantly increase the impact of diarrhoeal disease in the poorest populations (currently estimated by the WHO as 6.5 per cent of the total burden of disease in Africa and over 8 per cent in the poorest countries of SE Asia). The projected increase in precipitation variability may also increase diarrhoea morbidity by the contamination of water supplies.

  Health consequences of floods and droughts. Any increases in climate extremes (storms, floods, cyclones, etc) associated with climate change would cause physical damage, population displacement, and adverse effects upon food production, freshwater availability and quality, and upon the risks of infectious disease epidemics, particularly in developing countries. Over recent years a number of major climate-related disasters have occurred which have had major adverse effects on human health—including floods in China, Mozambique, and Bangladesh, famine in Sudan, and Hurricane Mitch which devastated Central America. Whilst these events cannot be confidently attributed to climate change, they indicate how vulnerable populations are susceptible to extreme weather. There is evidence that exposure to natural disasters may have long term impacts on mental health in adults and children.

  Malaria and other vector borne diseases. Malaria and other vector borne diseases are likely to increase their range in a warmer climate. This is already happening, but the relative importance of climate change, local changes in environment and population behaviour, and collapse of public health control measures, is unclear in most situations[17]. Changes in rainfall distribution throughout the year and its intensity are more important (and less predictable) for malaria transmission than temperature increases. There is good evidence that El Niño affects epidemic risk in certain regions[18]. The important extensions of actual malaria occurrence due to climate change, as distinct from the potential for malaria to be transmitted, are likely to be in those tropical countries with high altitude areas where the population of the hills are free from malaria but are surrounded by plains in which malaria is highly endemic. Here, the spread of both the vector and the malaria parasites can easily follow changes in climatic suitability. So far, extensions laterally into higher latitudes have been more due, at any rate in Asia, to failures of public health measures than climatic changes. Public health measures, well applied, should be able to control epidemics and unstable malaria at the edges of its distribution. Climate change is unlikely to have a large effect on the severity or transmission of malaria in those countries of tropical Africa where there is already massive transmission and suffering from the disease.

  Arboviruses (insect-borne virus diseases) provide a less predictable and perhaps more disturbing threat than does malaria in relation to global climate change. Climate change may facilitate their spread to the more temperate developing countries and it is less predictable which will emerge as major problems. Several arboviruses can give rise to fatal illness (for example, yellow fever, dengue haemorrhagic fever) for which treatment is not feasible and few have vaccines available.

3.  Which populations are the most vulnerable?

  There are many uncertainties in assessing the potential health impacts as climate change scenarios are highly uncertain at the spatial and temporal resolution most appropriate for health impact assessment. The largest source of uncertainty is the future world in which the climate impacts are felt—will it be more or less equitable with better or worse health care? Therefore, research activities have shifted towards identifying those populations most vulnerable to the health impacts of climate change. For example:

    —  Populations in currently malaria-free areas in the East African Highlands are vulnerable to increases in malaria associated with climate change.

    —  Populations in Bangladesh are vulnerable to health impacts of flooding associated with climate change.

    —  Populations in central America are vulnerable to increases in flood and landslide risk, and also drought risk, due to any increase in rainfall variability, including possible more frequent and intense El Niño events.

4.  Clean energy and the health benefits of mitigation policies

  Actions taken to reduce greenhouse gas emissions are very likely to benefit health. Fossil fuel combustion releases both local hazardous air pollutants (particulates, ozone, nitrogen oxides and sulphur dioxide) and greenhouse gases. Hence, policies to reduce greenhouse gas emissions via a reduction in vehicle exhausts or via an increase in the efficiency of indoor household cookstoves (particularly in low income countries) would yield substantial benefits to health. Controlling road traffic would also benefit health through reductions in road traffic accidents, a leading cause of death world-wide. The benefits to health from mitigation are highly dependent on the technologies and sectors that are involved. For example, a significant number of premature deaths could be prevented via reductions in particulate emissions in the household sector in China (ie domestic fuel use). Large numbers of people lack access to clean energy and suffer ill health and social disadvantage as a result. Renewable energy sources, particularly solar and wind, could help provide this much needed energy while minimising greenhouse gas emissions and maximising health gain. However, rigorous health impact assessment of renewable energy technologies should be undertaken in developing countries.

5.  Adaptation measures to reduce the potential health impacts of global climate change

  Adaptation measures can be used effectively to reduce greatly many of the potential health impacts of climate change. The most important, cost-effective and urgently needed measure is to rebuild public health infrastructure. Many diseases and public health problems that may otherwise be exacerbated by climate change could be substantially prevented with adequate financial and human public health resources. These resources would encompass public health training programs, research to develop and implement more effective surveillance and emergency response systems, and sustainable prevention and control programs. Low income countries already have spending well below that required to control infectious disease. According to the WHO Commission on Macroeconomics and Health the minimum level of health expenditure to introduce and maintain essential health interventions is US$34 per person in low income countries and US$38 per person in the least developed countries. Poor countries currently lack the needed financial resources to meet the most basic health needs of their populations.

  Current debate on adaptation specifically to reduce the health impacts of climate change has focused on the following areas:

    —  Improved use of climate information to forecast and control epidemics of malaria and other infectious diseases.

    —  Improved surveillance of diseases and disease vectors in order to detect any changes in distribution, seasonality or transmission intensity, or the emergence of new diseases.

    —  Disaster preparedness.

    —  Heat wave early warning systems.

  Epidemic forecasts begin with a crude prediction of epidemic risk several months in advance, derived from the long-range weather forecast. This forecast may be made more precise several weeks in advance using vegetation and other patterns on satellite images, allowing preventive and early response resources to be put in place. Research is being undertaken in East Africa to see how far this can be made an operational tool and there are also similar plans within India. These activities merit support since, once set up, the ongoing costs in terms of weather forecasting and satellite imagery are low. The key issue is linking information to response. The poorest populations are least able to remain in a state of perpetual readiness to cope with epidemics. Epidemic forecasting has the potential to really alleviate the hazards to which poorer populations are exposed.

  Capacity building for developing countries. Current efforts to support capacity building have focused on national Climate Change Vulnerability and Adaptation Assessments. However, health impacts have not been adequately addressed in most assessments, if at all, and the involvement of the health sector has been minimal. WHO is developing guidelines for developing countries to undertake health impact assessments for climate change that address health sector participation and capacity building. These activities could be supported by DFID.

London School of Hygiene and Tropical Medicine

January 2002

15   Climate change 2001: Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Eds McCarthy et al. CUP, New York. Back

16   Checkley et al. (2000) Lancet, 355, 442-4. Back

17   Kovats et al. (2001) Phil Trans Roy Soc B, 356: 1057-10. Back

18   Kovats (2000) WHO Bulletin, 78: 1127-1135. Back

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