PURPORTED IMPACT OF CLIMATE CHANGE ON HUMAN HEALTH 0 IUBIHUOBIIV September 19, 1996 D. J. Devlin - Exxon Biomedical Sciences, Inc. PRESENTATION OUTLINE Summarize Key Literature Re Purported Effects of Climate Change on Human Health Review/Assess ?Advocates? Hypothesis?: ?Greenhouse Gases? Lead to Health Impacts Balanced Scientific Position Not Evident Describe Key Knowledge Gaps Offer Conclusionisecommendations for Follow-up INTRODUCTION International Attention Focused on Relationships Among Greenhouse Gases, Climate Change, Ecological Stress and Human Health National Academy of Sciences (NAS) Sponsored Conference on Potential Impacts of Global Climate Change on Health (9195) Intergovernmental Panel on Climate Change (IPCC) Report Reviews "State of Knowledge" . . . Raises Significant Health Concern I Medical Journals Relate Climate Change to Incidence of Disease Popular Press Raising Issue of ?Megastorms? ?Global Fever? ?Emerging Infectious Disease? NAS CONFERENCE Conference Requested by VP Gore, to: Encourage Experts to Address Potential Effects of Climate Change on Disease, Heat Stress, Foolelater Supplies, Air Pollution Develop Response Strategies Organizers Assumed a Priori: Global Climate Change is Occurring Will Impact Health Only Degree ls Unknown Many Disciplines lnvOlved. . . Few "Experts" . Many,' "Advocates" With a Consistent Message THE HYPOTHESIS 1) Greenhouse Gases Increase Due Primarily to Fossil Fuel Use 2) Accumulation Leads to Increase in the Average Global Temperature . . . 1 - in the Next 100 Years 3) Global Warming Will Affect Ocean/Air Currents and Humidity, Lead to Climatic and Geographic Changes vv Wintertime Precipitation Increase More Severe Weather Events . . . Increased Rainfall Drought Increase in Number and Severity Northern Snow CoVer and Alpine Glaciers Decline Sea Level Rise (0.3 - 0.5 by 2100) El Ni?o-Southern Oscillation (ENSO) Increase Frequency THE HYPOTHESIS (cont'd) 4) Changes will Strain Major Ecosystems Decrease in Diversity of Species Increase in Number/Range of ?Opportunistic? Species Relocation, Possible Reduction, of Agricultural Sites 5) Human Health will be Qir_e?t_ly Impacted by Climatic Changes - Suffering and Death Due to Thermal Extremes Injury, Death Due to Weather-Related Disasters THE HYPOTHESIS (cont'd) 6) Human Health will be Indirectly Impacted by Physical and Ecological Changes Range/Activity of Disease Vectors and lnfective Agents Will Increase . . . Alter Range, Intensity and Seas?onality of Vector- Borne Diseases Increase in Water-Borne Diseases Through Disturbances in Fresh Water Ecosystems Population Displacement Due to Rising Sea Level, Regional Declines in Food Production, Weather Disasters . . . Lead to Increase in Malnutrition, Injuries, Infections, Civil Strife THE HYPOTHESIS (cont'd) Increase in Pollen and Spores . . . Lead to Increases in Asthma, Allergies and Other Respiratory Diseases Increase in Particulates and Ozone Increased Hospitalizations And-Deaths From Cardio-Pulmonary Diseases. 7) Combination of Infections, Malnutrition, and Social Stress, Especially in Displaced Groups, May Amplify Health Impacts I BASIS OF DIRECT EFFECTS 0 Sudden Extreme Increases in Ambient Temps Result in ?Excess? Deaths Elderly, Sick, Very Young Have Limited Physiological Capacity to Adapt Urban Poor Lack Escape from Exposure ?Urban Heat lsland Effect? ?J-Shaped? Relationship Between Daily Death Rates and Outdoor Temp. 0 ?Threshold Temperature? Proposed: Statistically Derived Temp. Beyond Which Mortality Rises Significantly Varies Regionally: 86? F, Deaths in NYC No Effect in Jacksonville, FL 0 Other Factors Exacerbate Effect of Heat: High Humidity, Low Wind, Solar Radiation ?Oppressive Umbrella of Air? Wintertime Deaths from Influenza and Hypothermia Predicted to Decrease I BASIS OF INDIRECT VECTOR-BORNE EFFECTS 0 Evidence Indicates Vector Organisms and lnfective Agents Sensitive to Climatic Natural Regulatory Forces Temperature: - Increase Accelerates Metabolic Rate Increased Biting Rate For Blood-Feeders, Increased Egg Production Longevity Of F_emale Mosquito Decreases Above 77? - Arthropods Have Optimal Range. . . Changes in Minimum Temp. Could Be Important BASIS OF INDIRECT VECTOR-BORNE EFFECTS (cont?d) Precipitation: Water Critical for Some Breeding Sites: Mosquitoes and Blackflies Have Aguatic Larvae/Pupae Stages Humidity: High Relative Humidity Favors Most Metabolic Processes of Vector Organisms, but infections of Vectors by Fungi Increase Wind: Contributes to Passive Dispersal of Flying Insects 0 Examples Cited Include: . Epidemics of Malaria Following Atypically Hot/Rainy Periods Emergence of Rodent-Borne Hantavirus in U.S. (1993) Occurrence of Dengue Fever Doubles with 3 - Rise Fig. 4.3. Variations In November temperature and annual talciparurn malaria rate In north-east Pakistan between 1981 and 1991 Mean November temperature 19" Annual ialciparum rate r6 18.17.16.1982 1984 1986 1988 1990 1992 Year Source: Bouma. Sondorp van der Kaay. 19949. Climate System. temperature precipitation Malaria System Mosquito System mosquito . Human System longevity climate change frequency of . . malaria transmission tential biting of humans p0 . . infection immunes Infected susceptibles loss of immunity mosquito density development of immunity - morbidity deaths diseased paras? - . development mortality Systems diagram of a model designed (adapted from Martenset 01., 1994). BASIS OF INDIRECT WATER-BORNE EFFECTS 0 Cholera a Major Concern Affected by Precipitation Extremes 0 Marine Plankton as ReservOir for V. cholerae Usually in Dormant State . Higher Sea Temperature Increased Plankton Population and- Reemergence of V. cholerae - Association Between El Ni?o and Cholera Outbreaks Activer Studied I 0 Diarrheal Diseases Peak During Hot/Wet Seasons KEY KNOWLEDGE GAPS General 0 Predictive Models Largely Unvalidated Direct Effects 6 Significance of ?Mortality Displacement? During Excessive Heat 0 Moderating Effect of Acclimation, Infra-Structural Changes Indirect Effects 0 Better Understanding of Complex Relationship Among Vector, Parasite, Human, and Climate Changes 0 Extent to Which Human Intervention Can Mitigate Potential Impacts of Climate Change on Health 619 CONCLUSIONS Balanced View Not Evident in Peer-Reviewed Journals, Public Media - General Consensus That Climate-Induced Changes in Public Health Extremely Difficult to Quantify Multiple Factors Lead to Wide "Natural" Fluctuations Predictive Computer Models Dif?cult to Validate, Do Not Reflect Adaptive Response ?Hypothesis? Advocates State Risks are High . . . "Precautionary Principle" Dictates that Lack of Scientific Certainty Can?t Justify Postponing Preventive Action - - CONCLUSIONS (cont?d) Minority View: Evidence Must be Weighed . .. . Plausible Mechanisms Defined . . .Relative Significance Assessed Climate Change is Likely a Marginal Factor. . . More Critical issues Exist: Malnutrition, Personal Hygiene, Drug Use, Food Prep, Urbanization, Population Growth, Trade and Travel, Evolution of Microbes, Inadequate Public Health 0 Impact of Climate Change on Human Health will Remain Speculative . . . Provides a Potentially Emotional Issue POTENTIAL NEXT STEPS Monitor and CritiqueOngoing Developments Identify and Critique Relevant Predictive Models Identify Scientific Leaders with Diverse Views . . . Encourage Active Participation in Debate - Promote Concept of Relative Risk . . . Significance of Climate Impacts Vs. Other Disease Factors