HEALTH CONSEQUENCES OF CLIMATE CHANGE

Transcription

1 HEALTH CONSEQUENCES OF CLIMATE CHANGE February 2008 Nicola Perrin, Strategic Planning and Policy Unit, Wellcome Trust

2 CONTENTS EXECUTIVE SUMMARY BACKGROUND Introduction Climate change 9 2. HEALTH IMPACTS OF CLIMATE CHANGE Extreme weather events Heat waves Floods Infectious diseases Vector-borne diseases Water-related diseases Animal health Immune disorders and respiratory diseases Air pollution Allergens Exposure to ultraviolet radiation Population crises Malnutrition Health problems of displaced populations Summary RESEARCH NEEDS NEXT STEPS FOR THE WELLCOME TRUST Work through partnerships Frontiers meetings Public engagement Environmental responsibility. 29 February

3 EXECUTIVE SUMMARY Context The scientific evidence is now overwhelming: climate change presents very serious global risks, and it demands an urgent global response. [Stern Review (2006)] 1. Climate change is receiving increasing international attention. The Intergovernmental Panel on Climate Change (IPCC) published the final part of its Fourth Assessment Report in November 2007, drawing together the latest evidence of the impacts of climate change. The UN climate change conference met in December to discuss a post-kyoto agreement, and the World Health Organization (WHO) is also increasing its focus on tackling the health impacts of climate change. 2. The issues are also high on the agenda of the UK Government, with the draft Climate Change Bill passing through parliament. Living with Environmental Change a major 1 billion partnership between the Research Councils and nine Government departments and agencies has recently been announced as part of the Comprehensive Spending Review The UK Collaborative for Development Science (UKCDS) has also identified climate change as a priority for its first year. 3. It is therefore timely to explore what, if anything, the Trust might do in terms of developing a research agenda around the health impacts of climate change. Some current Trust funding is already relevant, including much of the Trust s portfolio of infectious disease research, the Health Consequences of Population Change programme, Animal Health in the Developing World, and international public engagement activities. However, there may be opportunities for the Trust to begin to address specific research questions, to play a part in global collaborations, or to take further action to encourage environmental responsibility, both internally and among our research community. This paper provides background information about the potential health impacts of climate change, and presents the next steps for the Trust as agreed by Executive Board at a Strategy discussion in November. Climate change 4. The IPCC has concluded that warming of the climate is unequivocal. Following an international review by thousands of scientists, the IPCC predicts the following changes: average temperatures could rise by 2-3 C within 50 years extreme weather events heat waves, flooding, storms and droughts will become more frequent and more intense warmer temperatures will lead to increasing risk of abrupt and large-scale changes including melting of ice sheets and rising sea-levels the changes are happening much faster than initially predicted. 5. While mitigation approaches to reduce carbon dioxide emissions are still crucial, the focus of discussions is now shifting to consider adaptation as well introducing measures to adjust to the inevitable change. This focus on adaptation and vulnerability lies most within the scope of the Trust. February

4 Health impacts of climate change 6. Climate change is likely to affect the health status of millions of people. 1 Particular impacts include: Extreme weather events Heat waves the European heat wave in 2003 led to over 20,000 excess deaths in two weeks Floods extensive flooding across the globe this year has led to increases in infectious diseases, respiratory symptoms and mental health problems Malnutrition droughts and floods will have a devastating effect on already-scarce food supplies. Infectious diseases Changing distribution of vector-borne diseases, particularly malaria and dengue, is predicted to be very likely with rising temperatures Rodent-borne and water-borne diseases are also likely to increase Animal health will also be threatened 60 cases of bluetongue virus have been reported in the UK for the first time ever in 2007, partly as a result of weather conditions this year. Respiratory disease and immune disorders Increasing levels of ozone at ground level are a cause for concern, while changing levels of allergenic pollen are likely to lead to an increase in the incidence and intensity of allergic rhinitis. Increasing exposure to UV radiation Population displacement hundreds of thousands of people could be displaced as a result of water scarcity and rising sea levels, with significant health impacts. 7. Developing countries will be most severely impacted but have least capacity to respond. 8. There are still many uncertainties about the health impacts of climate change. Other socioeconomic and environmental factors will also have a significant influence and must not be ignored. It is important to note that it is not possible to attribute all health outcomes to climate change alone - climate change is just one contributing factor among many. However, the IPCC has concluded that evidence is growing that climate change already contributes to the global burden of disease and premature deaths. The predictions are summarised in Figure There are significant research needs to begin to understand more about the health impacts of climate change and to improve monitoring and modelling work. An improved evidencebase will be crucial to inform policy decisions about appropriate adaptation measures. 1 IPCC Working Group II (2007) Chapter 8 February

5 Figure 1: Direction and magnitude of change of selected health impacts of climate change 2 Next steps for the Wellcome Trust 10. A series of options for approaches that the Trust might take were developed through discussions across the Trust, and discussed by Executive Board in November It was agreed that the Trust should develop a research agenda relating to the health impacts of climate change, and the following actions will be taken forward: Work in partnership and through multidisciplinary collaborations to develop ideas, particularly with UKCDS partners and through the Living with Environmental Change programme. Arrange three high-profile meetings, in order to examine new areas and explore opportunities for future funding: o o o Mitigation / adaptation co-benefits (focusing on public health implications of changing energy supplies and efforts to reduce greenhouse gas emissions) Public health impacts of disasters (to include: research agenda following a disaster; how to ensure an appropriate public health rapid response ; and longer term mental health impacts) Environmental biotechnologies (the contribution of biotechnology for both mitigation and adaptation approaches, for example carbon-fixing bacteria, biofuels, crops, and addressing water shortages) 2 IPCC Working Group II (2007) Chapter 8. Confidence levels are assigned based on the IPCC guidelines on uncertainty. For further information see: February

6 Public engagement aspects should be included in all three meetings, and throughout future climate change work. Environmental responsibility: If the Trust is to become more involved in issues related to climate change, it will be important for the Trust to get its own house in order. Work to reduce the Trust s carbon footprint should continue, analysing the different components in more detail to determine where to focus efforts. The Trust should also consider whether it has a leadership role in encouraging the introduction of measures to make research practice and laboratory design more sustainable. February

7 1. BACKGROUND 1.1 Introduction 1. Climate change is likely to affect the health status of millions of people, according to the most recent report of the Intergovernmental Panel on Climate Change (IPCC). 3 Impacts include the changing distribution of vector-borne infectious diseases, such as malaria and dengue, and an increasing threat from extreme weather events, including flooding and heat waves. Those in low-income countries will be most severely affected. 2. There is increasing international debate about climate change, as the effects of global warming become more apparent. The Nobel prize-winning IPCC published the final conclusion of its Fourth Assessment Report in November 2007, raising awareness of the threats. 4 The UN Climate Change Conference, held in Bali in December 2007, considered international policy after the Kyoto treaty expires in Discussions, previously focused solely on mitigation approaches, are now beginning to consider adaptation as well, on the basis that some change is now inevitable Climate change is also high on the agenda of the UK Government: the Department of Health, the Department of the Environment, Farming and Rural Affairs (Defra), and the Department for International Development (DFID) are all actively discussing the issues. The draft Climate Change Bill is progressing through Parliament and a Climate Change Committee, to provide independent advice on how the UK can meet its climate change goals, has just been established. The UK Research Councils have announced a new Living with Environmental Change programme a major interdisciplinary research and policy partnership with Government departments to tackle environmental change, with 1 billion committed over ten years. The Royal Commission on Environmental Pollution has also announced that adapting to climate change in the UK will be its next major study. 4. The World Health Organisation (WHO) is giving increasing focus to issues related to climate change, and the Executive Board discussed the issues in January The UK Collaborative for Development Science (UKCDS) has identified climate change as a priority for its first year, providing opportunities to identify potential synergies with other funders. 5. It is therefore timely to explore what, if anything, the Trust might do in terms of developing a research agenda around the health consequences of climate change. Some current Trust funding is already relevant, including much of the Trust s portfolio of infectious disease 3 Confalonierie, U, Menne B, Akthar R, Ebi KL, Hauengue M, Kovats RS, Revich B, Woodward A (2007): Human health. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the IPCC, Parry ML, Canziana OF, Palutikof JP, van der Linden PJ, Hanson CD, Eds., Cambridge University Press, Cambridge, UK, Cited hereafter as IPCC Working Group II (2007) Chapter 8. 4 The final synthesis of the IPCC Fourth Assessment Report will be published in November Working Group I the physical science basis published its report in February 2007; Working Group II impacts, adaptation, and vulnerability, published in April 2007; and Working Group III Mitigation of climate change, published in May See for example, Prins G and Rayner S, Time to ditch Kyoto Nature (2007) 449: February

8 research, the Health Consequences of Population Change programme, Animal Health in the Developing World, and international public engagement activities. However, there may be opportunities for the Trust to begin to address specific research questions or to take further action to encourage environmental responsibility, both internally and among our research community. 6. This briefing document provides some background information about the health impacts of climate change which was prepared to inform a discussion at Executive Board. Information has been compiled from a range of reports and papers on the topic, including the IPCC Fourth Assessment Report (2007), the WHO report, Climate change and human health risks and responses (2003), and the UK Department of Health s impact assessment report Health impacts of climate change (2002, updated 2008). 6 A series of options for next steps were proposed to Executive Board, setting out a range of possible approaches the Trust might consider. These were developed through discussions with Trust staff, including a cross-trust brainstorm in October. A summary of the EB discussion, main recommendations and next steps is included in section The paper considers the impacts of climate change both in the UK and developing countries. Examples of related Trust funding are included throughout the briefing. 8. The focus of this background paper is on the health impacts of climate change, rather than the underlying physical basis of climate change. The conclusions of the IPCC s most recent Fourth Assessment Report compiled by more than 2,000 scientists internationally are taken to provide an accurate indicator of the potential level and impacts of future warming. The ongoing debate about the causes and attribution of global warming are outside the scope of this paper what is of most importance to the Trust is that effects are already seen to be happening. Similarly, international approaches to reduce greenhouse gas emissions and other mitigation policies, while crucial, are essentially beyond the Trust s remit and therefore lie outside the scope of this discussion. 9. The Stern report concluded that no one can predict the consequences of climate change with complete certainty; but we now know enough to understand the risks. This applies equally to the health consequences of climate change. Our understanding of the health impacts remains limited, and there are a significant number of social, economic and environmental factors that are likely to have a modifying influence. However, initial impacts are already being seen, and there is an urgent need to address adaptation. 6 Information in this document is taken from a wide range of sources, including: IPCC (2007) Fourth Assessment Report; Stern Review (2006) The economics of climate change ; Department of Health (2002, updated 2007) Health impacts of climate change ; WHO (2003) Climate Change and Human Health - Risks and Responses ; Harvard and UNDP (2005) Climate Change Futures: health, ecological and economic dimensions ; and papers including: Haines A, Kovats RS, Campbell-Lendrum D, Corvalan C, Lancet (2006) 367: ; McMichael AJ, Woodruff RE, Hales S, Lancet (2006) 367: ; Patz JA, Campbell-Lendrum D, Holloway T, Foley JA Nature (2005) 438: ; Watson RT, Patz J, Gubler DJ, Parson EA, Vincent JH J. Environ. Monit. (2005) 7: ; Haines A, Patz JA JAMA (2004) 291: February

9 1.2 Climate Change 10. There is near unanimous scientific consensus that the rising atmospheric concentration of greenhouse gases is warming the climate. 7 The IPCC Fourth Assessment Report 8 concludes that global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750, and now far exceed the natural range over the last 650,000 years as determined from ice cores. 9 The rate of growth of greenhouse gas levels is also shown to be accelerating. 11. Using a wide range of evidence including changes in temperature, rising sea levels and reductions in northern hemisphere snow cover the IPCC concludes that warming of the climate is unequivocal. It is also very likely that extreme weather events heat waves, heavy rains and flooding, storms and droughts will become both more frequent and more intense. 12. The Stern Review concluded that, on current trends, average global temperatures could rise by 2-3 C within the next fifty years. If emissions continue to grow, this increase could be several degrees more by The IPCC also estimates that temperatures will increase by between 1.8 and 4 C. With higher temperatures, the impacts are likely to be increasingly severe: increased warming will lead to an increased risk of abrupt and large-scale changes such as the collapse of ice sheets, shifts in El Niño phenomenon, or damage to the Amazon rainforest. It has also been noted that the changes are happening much faster than initially predicted. Warming at the artic is occurring twice as fast as across the rest of the globe. 13. Much of the public debate has focused on the causes of climate change, the role of anthropogenic greenhouse gas emissions, and the most effective methods for reducing emissions. However, there is now little doubt that warming is happening. There therefore need to be two main areas of discussion: mitigation (reducing emissions) and adaptation (adjusting to the change). While mitigation approaches will certainly be crucial, some change is now considered unavoidable and attention must therefore also be given to adaptation. It is this focus on adaptation and vulnerability that lies most within the scope of the Trust. 7 McMichael et al (2007) 8 Climate Change 2007: The Physical Science Basis. Contribution of Working Group 1 to the IPCC Fourth Assessment Report 9 The atmospheric concentration of CO 2 in 2005 was 379 ppm, compared to the natural range determined from ice cores of ppm. The IPCC has raised its conclusion from likely in 2001 to very likely in 2007 that most of the observed increase in global average temperatures in the past century is due to the increase in human-caused emissions of greenhouse gases. February

10 2. HEALTH IMPACTS OF CLIMATE CHANGE 14. The IPCC predicts that the health status of millions of people will be affected by climate change, through a number of routes, as shown in Figure 1. The impacts may be direct, through changing weather patterns and extreme weather events, such as heat waves, floods and forest fires. There can also be indirect effects, including changes in air quality, water, crop yields and agriculture, vector ecology and ecosystems. Abrupt and large-scale changes caused by climate change, for example rising sea levels or severe droughts, could lead to severe social and economic disruption with significant health impacts. However, it is important to note that social and environmental conditions may modify the impacts, as will the availability of health-systems and infrastructure. Figure 1: Pathways by which climate change affects health [source: IPCC, Working Group II, Chapter 8] 15. This section examines the predicted health consequences, including the impact of extreme weather events such as heat waves and flooding; the spread of infectious diseases (focusing mainly on vector- and water-borne diseases, although rodent- and food-borne diseases 10 may also increase); the effect of changing levels of air pollutants and allergens; exposure to ultraviolet radiation; and, finally, the large-scale impacts of malnutrition and population displacement. Each section examines current evidence, the likely health impacts and the need for further research. 10 Food poisoning is associated with warm weather. The Department of Health concluded that the predicted increase in UK temperatures is likely to be accompanied by an increase in cases of food poisoning. Improvements in food storage, preparation and hygiene could prevent this. February

11 2.1 Extreme weather events Heat waves 16. The IPCC predicts, with high confidence, that climate change will lead to an increase in the number and intensity of heat waves. Over the past few decades hot days, hot nights and heat waves have already become more frequent, as seen for example with the European heat wave in 2003 (see Box 1). 17. The relationship between temperature and mortality is shown in Figure 2. Above an optimum temperature for any given population, mortality rates will increase as temperatures rise outside this comfort zone. Figure 2: Temperature-mortality relationship, showing the potential effect of an increase in average annual temperature. [Source: McMichael et al Lancet (2006) 367: ] Note: distribution of daily temperatures would be shifted to the right. Additional heat-related deaths in summer would outweigh the extra winter deaths averted. 18. Heat waves are often associated with increases in mortality, as a result of cardiovascular, cerebrovascular and respiratory diseases. The elderly, mentally ill and children are most vulnerable. However, it is difficult to quantify the actual mortality impact of a particular heat wave because there is often short term mortality displacement many of the susceptible people would have died in the near future. Box 1: 2003 Heat wave in Europe In August 2003, Europe experienced its hottest summer since 1500.* Average temperatures were 3.5 C above normal, for two weeks. France was the worst hit, with 14,800 excess deaths, around 60 per cent of which were in those over 75. In Paris, deaths increased by 140 per cent. The UK reported 2091 excess deaths (an increase of 17 per cent), and Belgium, the Czech Republic, Germany, Italy, the Netherlands, Portugal and Spain also reported above average mortality rates. The 2003 heat wave was so severe that the number of deaths is considered to have been beyond that expected from short-term mortality displacement. *Haines et al (2006); Patz et al (2005); IPCC Working Group II (2007) Chapter 8 February

12 19. With predictions of an ageing population, the impact of more frequent heat waves is likely to be exacerbated, as rising numbers of elderly people will be at risk. Increasing urbanisation will also lead to greater risks the urban heat island effect means that temperatures in cities are often significantly higher than in rural areas. 20. The 2003 heat wave demonstrated the importance of early warning systems, a coordinated response, and heat wave plans, providing advice on behavioural measures to reduce risk. The European Commission is funding a project, EURO HEAT, to improve public health responses to extreme weather/heat waves to improve understanding and coordination of surveillance and alert systems The WHO has also identified the need to improve the understanding of factors affecting vulnerability, and to assess how other social and environmental factors influence the impact of extreme heat events. There are already a number of reliable datasets allowing the link between temperature and mortality to be investigated in more detail over long time periods, but the impact on urban populations and in developing countries needs further monitoring Floods The Trust is currently funding a Research Career Development Fellowship at LSHTM to explore the impacts of heat waves on mortality. 22. Flooding was the most frequent natural weather disaster worldwide between , killing almost 100,000 people and affecting over 1.2 billion 12 (see Box 2). Climate change is likely to increase the frequency of extreme rain and flooding, even if overall precipitation levels fall. 23. In the UK, the Foresight Report Future Flooding (2004) estimated that the risk of flooding will at least double by 2080, and could increase by up to twenty times. Numbers at risk of flooding could rise from 1.6 million to 3.6 million by Those in developing countries, especially in low-lying and coastal areas in South and East Asia, Africa and small islands will be particularly vulnerable. According to one estimate, a 3 C rise in temperature could lead to up to 300 million additional people at risk of flooding each year. 13 Box 2: 2007 Global Flooding Extensive flooding in Yorkshire, Gloucestershire and Oxfordshire in July dominated the headlines in the UK. However, South Asia and West and Central Africa also saw severe flooding, with devastating results. Heavy monsoon rains and flooding across South Asia led to rivers rising by over 10 metres, leading to thousands of deaths, and five million hectares of farm land left under water. In Bangladesh alone, 638 people died from drowning, snake bite and diarrhoeal disease. Nearly 90,000 cases of diarrhoeal disease were reported in three weeks in August. In India, 23 million people were affected, and there were 1,000 deaths. Across Africa, seventeen countries, including Ghana, Burkina Faso, Togo, Sudan and Uganda suffered severe floods, with hundreds of thousands of people remaining homeless EM-DAT (2006) 13 IPCC Working Group II (2007) Chapter 8 February

13 24. Flooding can have significant health impacts: Drowning and physical injuries: including electrocution and carbon monoxide poisoning in the clean-up stages after a flood. Growth of fungal spores causing respiratory symptoms: following Hurricane Katrina, the toxic moulds left in New Orleans led to health problems known as Katrina cough. Increases in infectious diseases: flooding can create new breeding sites for mosquitoes and other disease vectors; lead to increases of rodent-borne infections including leptospirosis and tularaemia; and trigger outbreaks of water-borne diseases such as cholera and other gastrointestinal infections, particularly in developing countries with poor infrastructure, for example if there is contamination of water supplies with sewage. Effects on mental health: studies in the US, Netherlands and UK have shown a consistent pattern of increased psychological problems among flood victims in the five years following a flood, including increases in anxiety and depression, and behavioural disorders in children. 14 These effects often have a long lasting impact but have received relatively little attention. The Trust has funded research into cognitive behavioural therapy and other psychological treatments to treat post traumatic stress disorder, and is recognised as one of the few funders of mental health research internationally. The Trust has also provided funding for research ethics training in the wake of the 2004 tsunami to enable a campaign to Prevent retraumatising the traumatised, and has funded a workshop to develop national and international ethical frameworks for research following a disaster. 2.2 Infectious diseases Vector-borne diseases 25. Climate change is expected to have a particularly strong impact on vector-borne infectious diseases. These diseases, including malaria, dengue, tick-borne encephalitis, and schistosomiasis, already cause major burdens on global health. However, the vectors mosquitoes, ticks and flies are climate sensitive. The most recent IPCC assessment concludes that climate change has already altered the distribution of some disease vectors and predicted, with high confidence, that there will continue to be an impact. 26. A number of climatic variables particularly temperature, humidity, rainfall, and the El Niño southern Oscillation (ENSO) are known to affect both pathogen and vector, for example 14 Floods, health and climate change: a strategic review. Tyndall Centre for Climate Change Research (2004), Working Paper 63; Ahern M, Kovats RS, Wilkinson P, Few R, Matthies F. Epidemiol Rev (2005) 27: February

14 altering reproduction and survival rates. 15 Climate change is expected to lead to a number of different changes in the distribution of vector-borne diseases: Geographical distribution: rising temperatures may mean that a vector becomes sustainable at different latitudes and altitudes, exposing new populations to a disease. 16 Seasonal transmission: changing temperatures may alter or lengthen the transmission season for a disease. Warmer temperatures can enhance vector breeding or reduce a pathogen s maturation period; warmer winters may allow more vectors to survive from one season to the next. On the other hand, very hot and dry conditions can reduce mosquito survival. Increased incidence resulting from changing water levels: mosquitoes need access to stagnant water in order to breed. Increasing numbers of floods may create new breeding sites; droughts and falling water levels can also lead to stagnant pools forming as lakes recede. 27. However, a number of other factors also affect the transmission of vector-borne infectious diseases. These may be socio-economic for example increasing population movements, the use of control interventions, herd immunity, drug resistance, malnutrition; or environmental including changes in land use, deforestation, changing agricultural practices and water management, or increasing urbanisation. The interaction between these factors is often complex, and there is considerable controversy as to the relative impact of climate change. 28. Despite this uncertainty, an increasing number of studies have now demonstrated evidence for the effects of climate change on vector-borne diseases. Malaria has received the most attention (See Box 3: Malaria in the Eastern African highlands), but other diseases, including Dengue, Ross River virus, and Rift Valley Fever have also been linked to climatic variation. The 2006 Foresight report, Infectious Diseases, preparing for the future, therefore concluded that there is consensus that some, and possibly many, infectious diseases of animals, humans and plants will be affected by climate change. 17 Further details are provided in Table Using a combination of epidemiological, geographical and demographic information and satellite imaging data, Professor Bob Snow and Dr Simon Hay have estimated that the population at risk of malaria in Africa will change from approximately 0.63 billion in 2005, to 0.87 billion in 2015 to 1.15 billion in However, they note that demographic changes and the rate of population growth is the most significant factor. 15 Information collated from: Foresight (2006) Infectious Diseases: preparing for the future ; McMichael et al (2006); Haines et al (2006), Department of Health (2007); WHO (2005) Using climate to predict infectious disease epidemics 16 The impact could be particularly severe if naïve populations, with no population immunity, are exposed to new diseases; or where infrastructure is lacking to respond to emerging diseases 17 Foresight (2006). See in particular T7.1: Climate change and diseases of plants, animals and humans: an overview. 18 Foresight (2006); Hay SI, Tatem AJ, Guerra CA, Snow RW, Population at malaria risk in Africa 2005, 2015 and 2030, Foresight T8.2 February

15 30. Snow and Hay have highlighted the importance of an evidence-based quantification of need in order to allocate resources for malaria control. The Trust is funding the Malaria Atlas Project (MAP), to develop global maps of malaria risk. The first aim is to assemble data to establish an epidemiological baseline in order to identify the global distribution of populations most at risk from malaria. The project will then develop scenarios for other influences, including climate change, population growth and urbanisation, in order to model their potential impact. 19 Box 3: Malaria in the Eastern African highlands Four sites in the eastern African highlands Burundi (Muhanga), Kenya (Kericho), Uganda (Kabale) and Rwanda (Gikongoro) which were previously malaria-free, have shown evidence of increased levels of malaria. A study proposed this rise was associated with local warming since the 1970s. The initial data was disputed, partly because of the difficulties of controlling for demographic changes and increasing levels of drug resistance. However, a more recent study has revised the results, using data from , and showed evidence of significant warming (0.5 c) trend at all sites.* Using both a biological and statistical model, the research suggested that a 3 per cent increase in temperature could, in theory, have led to an increase of per cent in mosquito numbers. * M Pascual, JA Ahumada, LF Chaves, X Rodo, M Bouma. Malaria resurgence in the East African highlands: temperature trends revisited. PNAS (2006) 103, 15: ; How is climate change shifting Africa s malaria map? Suad Sulaiman (August 2007) SciDev.net Table 1: Potential impact of climate change on vector-borne diseases Disease Vector Potential impact of climate change Malaria Mosquito Data from the Mapping Malaria Risk in Africa project suggests a 5-7 per cent increase in Africa by 2100, as a result of malaria becoming more prevalent at higher altitudes. It is also estimated that the prolonged transmission season could lead to overall increase in person-months of exposure risk to malaria of per cent in Africa by However, this model does not take non-climatic factors into account. 20 A range of other models project different impacts. A biological model suggests that based on IPCC 2001 specific climate scenarios there might be a global increase of million people living in a potential malarial transmission zone in 2080, representing a 2-4 per cent increase in number of people at risk from malaria Hay SI, Snow RW. The Malaria Atlas Project: developing global maps of malaria risk. PLoS Med (2006) 3:12 e Tanser FC, Sharp B, le Sueur D. Potential effect of climate change on malaria transmission in Africa. Lancet (2003) 362: van Lieshout et al (2004), quoted in IPCC Working Group II (2007) Chapter 8 February

16 China and Central Asia are likely to see the largest increase in risk. Dengue Mosquito Outbreaks are usually associated with high rainfall and humidity; warmer temperatures also increase the rate of viral replication, increasing the probability of transmission. Hales et al estimate that the number of people likely to be at risk from dengue in 2085 will be 5-6 billion, compared with 3.5 billion without climate change. However, the impact of human factors and increasing travel has not yet been fully incorporated into models. 22 West Nile Fever Mosquito Transmission appears to be associated with drought conditions, although the link is not well understood. The Foresight report concluded that the intensity of extreme weather events could facilitate increased transmission, and there was a theoretical possibility of emergence in the UK. Tick-borne encephalitis, Lyme disease Ticks Temperature and humidity are important determinants of tick distribution and there is already evidence that the vector is moving to higher latitudes and higher altitudes in Europe, for example in Sweden. However, socioeconomic factors and changing agricultural practice may also be involved. 23 Leishmaniasis Sand-flies Climate change could have a direct impact on sand-fly distributions; changes in land use patterns will also have an impact. Geographical distribution of vectors in parts of Latin America and in Southwest Asia could increase. 24 Schistosomiasis Water-snails Regional warming is thought to have contributed to a recent epidemic of schistosomiasis in China, and there are concerns the infection could expand into the country s northern territories. 25 Increased temperatures shorten the reproductive cycle for both snails and worms, leading to increased numbers of both pathogen and vector. 31. Research needs: The WHO concluded that changes in infectious disease transmission patterns are a likely major consequence of climate change. The report went on to recommend there is a need to learn more about the underlying complex causal relationships, and apply this information to the prediction of future impacts, using more complete, better validated, integrated, models. 22 Hales et al (2002). From IPCC Working Group II (2007) Chapter 8 23 Randolph, SE and Rogers DJ. Proc. Roy. Soc. Lond. B (2000) 267: 1741; Randolph SE Phil Trans Roy Soc B (2001) 365: Patz et al (2004) 25 Scientists: Warming could increase schistosomiasis, SciDev.net, 11 April 2007 February

17 32. Two main types of modelling have been used to predict the impact of future climates on vector-borne diseases 26 : Statistical: using an empirical approach based on current epidemiology. Present day distributions of vectors are statistically matched to current climatic variables this understanding is then applied to future climate scenarios to predict future distribution. Biological using a mechanistic approach, aggregating the effect of climate on the individual components of the disease transmission cycle. 33. Other models also take habitat into account using landscape-based modelling, or compare regions with similar climatic envelopes. However the quantitative understanding is still poor. It will be important to improve modelling capacity, and to incorporate non-climatic factors into models, including potential prevention and control measures. 34. There also need to be improvements in surveillance, with enhanced detection, identification and monitoring. 27 It will be crucial to improve the collection of national and regional data to monitor changes in local conditions more accurately. The Foresight report identified the challenges involved in developing simple and cheap diagnostic devices, and using novel technologies for the detection and analysis of infectious diseases. 35. Thirdly, effective treatment, prevention and control measures will become increasingly important. The management of deforestation and surface water, improved case surveillance and treatment in fringe areas, and the introduction of insecticide-treated bednets could help to offset the increased risk due to climate change. The Trust has provided approximately 150 million to malaria research over the past five years, including funding for Bob Snow and the Malaria Atlas Project. Five of the top ten most highly cited researchers in the field of malaria to the end of 2005 were funded by the Trust. Other vector-borne infectious disease related-funding includes 7 million to Dengue, and 4.5 million for tick-related diseases from The Trust has funded Professor Sarah Randolph to explore the biological, iatrogenic and socio-political factors in the recent up-surge of tick-borne encephalitis (TBE) and Lyme disease in the Baltic States. The collapse of the communist system, with resulting changes in land-use patterns, provides an alternative explanation to the spread of TBE Water-related disease 36. Water-related diseases include both water-borne (transmitted by ingestion) and waterwashed (caused by lack of hygiene) diseases. The IPCC predicts that the burden of both types will be altered by climate change as a result of changes in rainfall, surface water availability and water quality. There are a number of routes: higher temperatures could have an effect on the microbiological and chemical contamination of water supplies; extreme rainfall events and flooding could lead to contaminated water supplies and facilitate water-borne outbreaks of disease; the incidence of diarrhoeal disease is sensitive to temperature and rainfall. 26 Department of Health (2007); WHO (2005) Using climate to predict infectious disease epidemics ; Haines et al (2006) 27 Foresight (2006); House of Lords Science and Technology Committee (2003) Fighting infection February

18 37. It is estimated that climate change will increase the risk of diarrhoeal diseases by up to 10 per cent in some regions by Currently, more than one billion people do not have access to safe drinking water. 29 Climate change is likely to increase levels of water stress. Water scarcity may also lead to the same source of water being used for a range of purposes, increasing the likelihood of contamination. 38. Outbreaks of cholera are often associated with higher temperatures. A growing amount of work recently has attempted to understand the environmental factors that influence the distribution of cholera, and to understand the link with plankton blooms, which are triggered by warmer sea surface temperatures. 30 Work in Bangladesh has used satellite imaging together with in situ meteorological data and cholera case data to provide evidence that cholera cases occur following a rise in sea temperature (Figure 3). Figure 3: Relationship between sea surface temperature and cholera case data in Bangladesh, from January to December Source: Colwell, RR. Global climate and infectious disease: the cholera paradigm. Science (1996) 274: However, studies of the links between climate change and water-borne disease are still at an early stage. Both WHO and the Department of Health have identified the need for improved monitoring, and further information on long-term trends is necessary in order to improve understanding and predictions about the impact of climate effects Animal health 40. The Foresight report on infectious diseases suggested that the picture will be mixed, with the risk of some livestock diseases increasing while others are likely to decrease. 31 There are also a number of other factors that may lead to changes in distribution of livestock pests and diseases, including international trade and commerce. 41. The spread of bluetongue virus in particular has been linked to trends in warming, with the virus range increasing significantly across northern Europe since It has been 28 WHO (2003) 29 Watson et al (2005) 30 Huq A, Sack RB, Nizam A, Longini IR, Nair GB, Ali A, Morris JG, Khan MNH, Siddique AK, Yunus M, Albert MJ, Sack DA, Colwell RR. Appl. environ. microbiol. (2005) 71: Foresight (2006) Infectious Diseases: preparing for the future ; February

19 suggested that rising temperatures have allowed the virus to persist during the winter and also led to the virus being transmitted by novel temperate vectors indigenous European Culicoides species, rather than the main African vector, Culicoides imicola enabling it to be spread over a larger geographical area In the past month, bluetongue has reached the UK for the first time, with cases now confirmed at 60 premises in Kent, East Anglia and Sussex. 33 While climate change is unlikely to be responsible for the arrival of the virus in the UK, the warmer temperatures provide a more favourable environment to allow the establishment and then spread of the disease. The impact is likely to be particularly devastating in animal populations that have not previously been exposed. 43. The crossover of diseases from wild animals to livestock, and from livestock to humans means animal health is also increasingly a public health issue. The increasing need for improved surveillance of emerging diseases in animals has been identified, given the rising importance of zoonoses. The 10.7 million Strategic Award to boost veterinary research training, announced in September 2007, recognises the importance of veterinary research both for animal health and human health, with climate change exacerbating the threat of emerging diseases. The Trust, together with NERC, MRC, BBSRC and ESRC, is holding a joint workshop on Environmental change and infectious diseases in March The meeting will examine how environmental change will affect the dynamics of human and farmed animal diseases that have reservoirs in the environment and what responses are needed to such changing dynamics? Box 4: Migratory birds and infectious diseases It has been suggested that migratory birds may play a role in the transmission of infectious diseases, including avian flu. If climate change is likely to have an impact on migratory birds, how might this affect the spread of disease? Climate change is likely to effect the breeding dates and migration seasons of several birds, and also to alter their geographical range. The IPCC has identified two possible consequences: 1. changed migratory patterns could lead to a shift in the geographical distribution of the vectors and pathogens 2. changes in the life cycles of bird-associated pathogens, due to changes in the breeding patterns of both wild birds and vectors (e.g. mosquitoes) Improved understanding of the role of migratory birds in the spread of disease, and the potential impacts of climate change on their routes, may be necessary as part of global efforts to prepare for a human influenza pandemic. However it is likely that the trade in livestock plays a larger role in transmitting disease. 32 Purse BV, Mellor PS, Rogers DJ, Samuel AR, Mertens PPC, Baylis, M. Climate change and the recent emergence of bluetongue in Europe. Nature Reviews Microbiology (2005) 3: October 2007 February

20 2.3 Immune disorders and respiratory disease Air pollution 44. Climate change will cause changes in the levels of air pollutants, the main concern being that higher temperatures are likely to lead to increased levels of ground-level ozone. 34 Ozone is associated with a wide range of adverse respiratory conditions, including nonspecific respiratory effects (coughing, airway irritation), reductions in lung function, aggravation of asthma in sensitive individuals; and the worsening of symptoms of existing emphysema and bronchitis. Prolonged exposures to ozone may also lead to permanent structural and cellular damage to the respiratory tract. 45. Much of the concern has been focused in the UK and developed countries. Urban air quality in the UK has been extensively reviewed over the past decade, and the Royal Society is also currently preparing a report on ground-level ozone. 35 The Department of Health has estimated that by 2020, using predicted levels of UK emissions and current climate change models, ozone could lead to more than a 50 per cent increase in attributable deaths and hospital admissions for respiratory diseases. However, if the climate remained at 2003 temperatures, the increase would only be 14 per cent It remains difficult to predict the impact of future concentrations of air pollution. Models need to take into account the levels of emissions of both primary and precursor pollutants; meteorological factors, including wind and temperature, that affect the dispersal of pollutants; and the potential health impacts of predicted pollutant levels. Future emissions will also depend on economic development, local regulations and population growth. In 2002 the Department of Health recommended that there was a need to understand both the short and long-term effects of ozone in more detail. 47. With the exception of ozone levels, it is anticipated that levels of air pollution in the UK will, in general, decrease. In addition, the reduction in the use of fossil fuels, and increasing use of renewable energy technologies, could reduce exposure to air pollution (see also further discussion of potential co-benefits of mitigation and adaptation approaches in section 4.2 below). However, worldwide, increasing numbers of forest fires and biomass burning could lead to increased levels of respiratory disease. Following forest fires in Malaysia and Indonesia in 1998, when 7500 km 2 were destroyed, the concentration of hazardous-size aerosol particles increased significantly. It was reported that 300 million people were affected; a 70 per cent increase in patients with worsened symptoms of respiratory diseases was reported; and the resulting air pollution was thought to be responsible for over 260 deaths from respiratory diseases, together with diarrhoea, skin disease and eye irritation. 37 The Trust is currently funding an intermediate clinical fellowship, for 450,000, to investigate the effects of chronic air pollution exposure on respiratory and cardiovascular mortality in the UK. 34 At 20 c, ground-level ozone levels are in the region of 60 ppb, at 35 c, levels rise to 180 ppb. Ozone levels from ppb can increase risks of health impacts. Watson et al (2005) Department of Health (2007) 37 Watson et al (2005) February

21 2.3.2 Allergens 48. Climate change is predicted to impact on levels of allergenic pollen in a number of ways: increased atmospheric carbon dioxide leads to increased release (through enhanced fertilization ) of pollens such as ragweed; changes to the timing and duration of the pollen season. The IPCC report found, with medium confidence, that the seasonal distribution of the spring pollen season has already been altered, with the season beginning earlier and continuing for a longer period; the geographic range of pollen allergens could also extend. 49. These changes can be expected to lead to an increase in the incidence of allergic rhinitis, possibly with an increase in both the intensity and duration of symptoms Exposure to ultraviolet radiation 50. Concerns that depletion of the stratospheric ozone layer would lead to increasing exposure to damaging ultraviolet (UV-B) radiation were highlighted in the 1980s. Governments acted internationally and successfully to reduce the production of industrial halogenated chemicals, through the Montreal Protocol. As a result, scientists have predicted that the ozone layer should recover by However, climate change may now delay this recovery and increase population exposure to UV in a number of ways: increasing temperatures may slow the recovery of the ozone layer, by causing stratospheric rolling; decreases in cloud cover could lead to increased exposure to UV-B; changes in behavioural patterns (particularly in the UK), with longer summers and increased outdoor activity, could also increase exposure There is evidence that exposure to UV-B radiation can lead to increased risk of skin cancer and incidence of cataract. The UN Environmental Programme has also suggested a mechanism by which exposure to UV radiation may cause immune suppression. The IPCC notes that if immune function is impaired, it could lead to reduced vaccine efficiency, which could further exacerbate the effects of climate-related shifts in infections The Department of Health report identified a considerable body of research evidence on the health effects of exposure to UV radiation, and recommended that campaigns to improve public awareness of the need to reduce personal exposure remain the most effective way to reduce the health risks. However, it has been suggested that further research is needed to understand more about the best ways to change behaviour and to ensure the efficacy of public health campaigns. 38 IPCC Working Group II (2007) Chapter 8. Watson et al (2005); Haines et al (2004), McMichael et al (2006) 39 World Meteorological Organization (2003) Scientific assessment of ozone depletion: global ozone research and monitoring project report No. 47. Geneva. 40 WHO (2003); Department of Health (2002) 41 IPCC Working Group II (2007) Chapter 8 [8.2.10] February