Climate Change and Public Health

Over the past years, there has been a general disagreement between those who believe in the global warming and those who don’t. Unfortunately, if true, the climate change could work like a chain reaction, which the final products would be harmful effects on people’s health. Therefore, global warming’s influences on the public health has become a major area of research. Scientists and governments concur that the Earth is warming; rapid global climate change is underway, and human activities are very likely the main cause. Scientists have tried to bring about numerous verifications to prove that the climate change is happening, and examples of its effects have been widely reported. In a way, its major primary effects are on the surface temperature of the Earth and the amount of precipitation. According to the National Climatic Data Center, all records indicate that during the past century, global surface temperatures have increased at a rate near 0.6°C per century, but the trend has been 3 times larger since 1976. (1) The results of this warming on regional climate are not uniform. In general, land-surface temperatures are increasing faster than sea-surface temperatures. (1) The climate in latitudes between 40°N and 70°N is warming more quickly than that in lower latitudes, and some areas are actually cooling. Changes in precipitation that occur with climate change are also nonuniform. (2) Since 1900, precipitation has increased 5% globally. Glaciers are in rapid retreat, and Arctic sea ice is melting. As a result of thermal expansion, sea level has increased 1 to 2 mm/year over the past 100 years. (2) There has been great number of studies trying to grasp the details of the climate change in different parts of the world. Simply put, the frequency of change varies in different parts of the world, but the general idea is the same everywhere.

Understandably, unnatural (man-made) changes in climate would in turn influence the living organisms in different ecosystems since they have not yet evolutionary adapted to these changes. The changes in ecosystems would finally have adverse effects on the public health since human population is in constant contact with diverse ecosystems of the nature. The list of the possible difficulties and illnesses the global warming would have on the public health is as follows:

1. Thermal stresses, which could cause either death or injuries from floods, storms, and cyclones. From 1992 to 2001, there were 2257 reported disasters due to droughts or famines, extreme temperature, floods, forest fires, cyclones, and windstorms. The most frequent natural weather disaster was flooding (43%), killing almost 100,000 people and affecting over 1.2 billion people

2. Microbial proliferation, which could cause food poisoning

3. Changes in vector-pathogen-host relations and in infectious diseases like malaria or dengue

4. Impaired crop, livestock and fisheries, which could lead to impaired nutrition (3)

 Of course, the long list could go on since any of these health problems could have consequences such as loss of livelihoods among people, displacement, poverty, or mental health illnesses. Since exploring each and every subject of this list would take substantial time and space, the following paragraphs will specifically look at the effects of infectious diseases, heat-waves, floods.

Climate constrains the range of infectious diseases, while weather affects the timing and intensity of outbreaks. Studies show that a warming and unstable climate is playing an ever-increasing role in driving the global emergence, resurgence and redistribution of infectious diseases. (4) Climate change will affect the potential incidence, seasonal transmission, and geographic range of various vector-borne diseases. These diseases would include malaria, dengue fever, and yellow fever (all mosquito-borne), various types of viral encephalitis, schistosomiasis (water-snails), leishmaniasis (sand-flies: South America and Mediterranean coast), Lyme disease (ticks), and onchocerciasis (West African river blindness, spread by black flies). (4) There are several examples to show or estimate the possible influences of global warming on the vectors. While inadequately studied in the US, warm winters have been demonstrated to facilitate overwintering, thus northern migration of the ticks that carry tick-borne encephalitis and Lyme disease. (5) In several studies that have modeled seasonal changes in transmission researchers estimate a substantial extension—such as a 16–28% increase in person-months of exposure to malaria in Africa by 2100. Three research groups have estimated how climate change will affect dengue fever. Early models were biologically based, driven mainly by the known effect of temperature on virus replication within the mosquito. Warmer temperatures shorten the time for mosquitoes to become infectious, and increasing the probability of transmission. Studies with both biologically based and statistical models project substantial increases in the population at risk of dengue. (3 and 5)

Extreme weather events include periods of very high temperature, torrential rains and flooding, droughts, and storms. Over time, populations adapt to the local prevailing climate via physiological, behavioral, and cultural and technological responses. However, extreme events often stress populations beyond those adaptation limits. Most studies of extreme temperatures and their relation with the population’s health have been done in Europe and North America. The way temperature affects people differs by gender, age, latitude, climatic zone, and socioeconomic situations. Studies show that the elderly, women, children, and mentally ill individuals are more prone to death or illnesses caused by extreme weather conditions. Generally, people in hotter cities are more affected by colder temperatures, and people in colder cities are more affected by warmer temperatures. (6) For instance, In the UK and some other northern high-latitude countries, seasonal death rates and illness events are higher in summer than in winter. The striking mortality excess (about 30,000 deaths) during the extreme heat wave of August 2003, in Europe, especially France, proves the lethality of such events. (3) As mentioned above, socioeconomic status of individuals could influence their survival in the case of extreme weather events. In 2003 in Paris many nursing homes and other assisted-living and retirement communities were not air-conditioned, and elderly residents might not have been promptly moved to air-conditioned shelters and rehydrated with fluids. There are currently studies going on to estimate such effects of the global warming in the future. One such study, for example, has estimated that major cities in Europe and northern USA will have substantial rises in both frequency and duration of severe heat-waves by 2090. Another one shows that in Australia, for a medium-emissions climate change setting in 2050, the annual number of deaths attributable to excess heat in capital city populations is expected to increase by 50% to 1650. (7 and 3)

As mentioned above, climate change has already caused sea-level rise and an increase in the annual precipitation rate around the world. These two conditions could cause flooding and potential human health disasters for the populations living close to rivers, seas, or the oceans. Floods are low-probability, high-impact events that overwhelm physical infrastructure, human resilience, and social organization. Floods result from the interaction of rainfall, surface run-off, evaporation, wind, sea level, and local topography. Some health consequences arise during or soon after the flooding such as injuries, communicable diseases, or exposure to toxic pollutants, whereas others like malnutrition and mental health disorders occur later. Moreover, excessive rainfall facilitates entry of human sewage and animal wastes into waterways and drinking water supplies, causing water-borne diseases. (3 and 7)

Infectious diseases, heat-waves, and floods are only a few of the many public health disasters which could be related to the global warming. It seems that human ignorance and his historic inefficiency are going to hunt him down if the rapid climate change is not being reversed. What matters is the current generation’s choice. The human population could either start believing the serious facts and evidences, and move towards a healthier life-style for itself and for the Earth, or simply accept that the few generations coming after us are possibly the last ones.

 

 Resources:

 

 1. C Parmesan and G Yohe, A globally coherent fingerprint of climate change impacts across natural systems, Nature 421 (2003), pp. 37–42.

2. FC Curriero, KS Heiner, JM Samet, SL Zeger, L Strug and JA Patz, Temperature and mortality in 11 cities of the eastern United States, Am J Epidemiol 155 (2002), pp. 80–87.

3. McMichael, R. Woodruff, S. Hales. Climate change and human health: present and future risks, The Lancet 367, pp. 859-869.

 4. Leaf A., Potential health effects of global climate and environmental changes, N. Engl. J. Med. 321, (1989) pp.1577–1583.

 5. McCarthy J.J., Canziani O.F., Leary N.A., Dokken D.J., White K.S., Climate change 2001: Impacts, Adaptation and Vulnerability. Working group II. Third assessment of the IPCC, Cambridge University Press, Cambridge, (2001), pp. 812–814.

 6. Epstein p., Climate change and emerging infectious diseases, Microbes and Infection 3, (2001), pp. 747−754.

 7. McGeehin M. and Mirabelli M., The potential impacts of climate variability and change on temperature-related morbidity and mortality in the United States, Environ Health Perspect 109 (2001), pp. 185–189.