Impact of Climate Change on Human Health

There is a close link between local climate and the occurrence or severity of some diseases and other threats to human health. Extreme temperatures can directly cause the loss of life. Moreover, several serious diseases appear only in warm areas. Finally, warm temperatures can increase air and water pollution, which in turn harm human health. The most direct effect of climate change would be the impacts of hotter temperatures themselves. Extremely hot temperatures increase the number of people who die on a given day for many reasons: People with heart problems are vulnerable because their cardiovascular system must work harder to keep the body cool during hot weather. Heat exhaustion and some respiratory problems increase. Higher air temperatures also increase the concentration of ozone at ground level. The natural layer of ozone in the upper atmosphere blocks harmful ultraviolet radiation from reaching the earth's surface; but in the lower atmosphere, ozone is a harmful pollutant.  Ozone damages lung tissue, and causes particular problems for people with asthma and other lung diseases. Even modest exposure to ozone can cause healthy individuals to experience chest pains, nausea, and pulmonary congestion. In much of the US, a warming of four degrees (F) could increase ozone concentrations by about 5 percent (US EPA).

Statistics on mortality and hospital admissions show that death rates increase during extremely hot days, particularly among very old and very young people living in cities. In July 1995, a heat wave killed more than 700 people in the Chicago area alone. Studies based on these types of statistics estimate that in Atlanta, for example, even a warming of about two degrees (F) would increase heat-related deaths from 78 annually now to anywhere from 96 to 247 people per year. If people are able to install air conditioning and otherwise acclimatize themselves to the hotter temperatures, the lower estimate is more likely. Warmer temperatures are likely to decrease the number of people who die each year from cold weather. However, in the United States, only 1000 people die from the cold each year, while twice that many die from the heat (US EPA). Also the estimates from death from heat stroke or similar causes listed on death certificates are likely to underestimate greatly increased mortality from heat stress as most of the large statistical jumps in death rates during very hot periods are likely to be attributed to respiratory disease or some cause other than heat stroke. Extensive analyses have been done of potential mortality risks in the US and China from heat stress in a greenhouse enhanced world and these indicate that thousands of lives may be at risk in each country.

Global warming may also increase the risk of some infectious diseases, particularly those diseases that appear only in warm areas. Deadly diseases often associated with hot weather, like the West Nile virus, Cholera and Lyme disease, are spreading rapidly throughout North America and Europe because increased temperatures in these areas allow disease carriers like mosquitoes, ticks, and mice to thrive. For instance, the number of cases of West Nile in the US and Canada have ballooned exponentially since 1999. Some scientists believe that algal blooms could occur more frequently as temperatures warm--particularly in areas with polluted waters - in which case diseases such a cholera that tend to accompany algal blooms could become more frequent (US EPA). Malaria, too, is rare in the United States even in warmer regions where the mosquito that transmits the disease is found, because this nation has the ability to rapidly identify and contain outbreaks when they appear. However, a 2005 study by the World Health Organization indicated that global climate change is directly tied to increased rates of malaria, malnutrition, and diarrhea. It estimated that climate change contributes to 150,000 deaths and 5 million illnesses each year.

Heat-related deaths can be prevented by emergency measures to move vulnerable people to air-conditioned buildings, and by reducing the emissions of photochemical oxidants which cause ground-level ozone. Many of the impacts of climate change on health could be avoided through the maintenance of strong public health programs to monitor, quarantine, and treat the spread of infectious diseases and respond to other health emergencies as they occur. Unfortunately the occurrence and geographical scope of these "vector-borne" diseases have mushroomed far quicker than scientists first projected. A 2005 Harvard study led by Dr. Paul Epstein discusses the increased health risks to humans as a result of the global warming and the speed at which these new and old diseases are spread across the globe.

Adverse impacts of climate change on human health are greater in poorer countries that lack the financial resources for air conditioning and that have less established public health networks. In 2005 a team of scientists compiled a map forecasting the likely future effects of climate change on human health in regions throughout the world. The map indicates that the unindustrialized world, much more than the industrialized world, will see itself suffering higher increases of disease and other human hazards due to the fact that they are both less equipped to deal with these issues and are geographically more likely to encounter them. It is conceivable that a significant indirect adverse health effect of climate change for richer countries may be the surge of migrants from poorer countries across borders as a result of catastrophic climatic events such as droughts, floods or severe storms.  A pulse of sudden migration of desperate people may bring diseases that could overwhelm public health resources of the nations where they flee. As Myers and Kent (1995) note, "There could also be substantial outlays to counter pandemic diseases and deficits of food, water and energy, together with the additional social strife and political turmoil these would entrain."

Impact of Air Pollution and UV Radiation on Human Health

It is estimated that air pollution causes several hundred thousand deaths a year around the world. Although there is some controversy over the magnitude, some highly regarded academic experts have estimated that even with the US Clean Air Act, among the most stringent air quality laws in the world, as many as fifty thousand Americans annually die prematurely as a result of air pollution. Perhaps the leading cause of air pollution related death in both industrialized and developing countries is particulate matter - soot and dirt particles that cause respiratory failure. Another major health concern is ground level ozone often experienced as urban smog. This can cause premature death and is the source of considerable discomfort and lost workdays in cities around the world. Lead emissions from gasoline have impaired intelligence of children and this realization has caused many countries to move toward a phase out of lead in fuels. Sulfur dioxide emissions may place asthmatics and others with respiratory disease at risk. Generally the elderly and children are the most vulnerable groups. Just over 50 years ago the US was shaken by an air pollution disaster in Donora, a small Western Pennsylvania town that claimed 50 lives in a few days. Air pollution today poses risks to millions worldwide, especially children in the world's largest cities. A symposium held in Washington, DC in February 2000 highlighted the gravity of the air pollution problem in China.

Ultraviolet radiation which will increase as a result of depletion of the stratospheric ozone layer has a number of adverse effects on human health including increased risks of various forms of skin cancer, weakening of the human immune system and increased risk of eye disorders such as cataract problems.

Potential of Climate Protection Policies to Enhance Human Health by Reducing Air Pollution Related Deaths and Illnesses

Policies and measures to reduce emissions of greenhouse gases are also likely to have other non-climate related effects on human health.  Many strategies such as those encompassing enhanced energy efficiency and movement to non-carbon fuels may also have sizable air quality benefits, particularly reduced deaths from exposure to inhalable particles. An international group of health scientists estimated in 1997 that the adoption of moderate carbon emission control policies worldwide would reduce deaths from particulates alone by about eight million between 2000 and 2020. The IPCC and several other groups including the Climate Institute in March 2000 organized a workshop in Washington on ancillary benefits and costs of greenhouse mitigation policies. Research is needed to get an understanding of likely ancillary effects, i.e. benefits and costs in areas other than climate protection of greenhouse emission mitigation policies.

Interrelations among Air Pollution, Stratospheric Ozone Depletion and Climate Change

There are complex interrelationships involving air pollution, stratospheric ozone depletion and climate change. Human industrial and agricultural activity has been a driving factor in contributing to each of these problems. In a number of instances actions to limit emissions to address one problem will have effects on others as well.

Chlorofluorocarbons (CFCs) that are the leading cause of stratospheric ozone depletion are also powerful greenhouse gases so actions to curtail their use will help in climate protection as well as in preserving the stratospheric ozone layer. Similarly actions to substitute renewable energy for fossil fuels or to increase energy efficiency in order to protect the climate are likely also to result in an improvement in air quality.

Sometimes, however, there are tradeoffs between these objectives as control measures are directed toward one objective. Scrubbers on coal-fired power plants to reduce air pollution may result in more energy consumption and an increase in greenhouse emissions. Both increases in global mean surface temperature and depletion of the stratospheric ozone layer are likely to affect the photochemical reactions that create ground level ozone or smog and in most cases aggravate the air pollution problem, to some extent negating the effectiveness of many air pollution control measures. (Article on interrelationships among air pollution, UV and climate change).

 

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