Overconsumption and health

Martin Hartog explores the health effects of global warming and outlines what individuals can do to help reverse the process

Overconsumption is the opposite of sustainable development. It means releasing or taking up more of something than can be tolerated by the biosphere, so causing environmental degradation. By reducing the capacity of the biosphere, a downward spiral occurs as more and more damage is done to the environment by the unsustainable actions of individuals. This phenomena has been named Carson's syndrome¹ after Rachel Carson, whose 1962 book Silent Spring exposed the toxicity of pesticides.² In this article the use of energy will be used as an example of overconsumption.

Global warming

Global warming is an effect of overconsumption. The earth is, in effect, a closed system, which has been in equilibrium for millennia with the sun as the ultimate source of energy. Short wave solar energy penetrates the earth's atmosphere but long wave, infrared, radiation emitted from the earth's surface is absorbed by atmospheric gases, the so called greenhouse gases (GHGs). These include carbon dioxide (CO₂; the main one), methane, and nitrous oxide. There is a natural greenhouse effect which means that the planet is about 33°C warmer than it would otherwise be.

It is widely held, especially by scientists from the United Nation's Intergovernmental Panel on Climate Change (IPCC), that that there has been a rise of average mean surface temperature of about 0.6°C since the late 19th century.³ The 1990s was the warmest decade since instrument records began in 1861, and 1998 was the hottest year ever recorded in the United Kingdom. Scientists of the IPCC also believe that this warming has been caused by human activities, especially industrialisation and the burning of fossil fuels and changes of land use, such as deforestation, which have caused an increase in the release of GHGs. Thus, atmospheric CO₂, the level of which was 260 parts per million (ppm) in preindustrial times, is currently about 370 ppm. During the period 1990-2100 a rise of 1.4­5.8^oC is predicted. How will this affect health?

Health effects of global warming

There are a large number of likely health effects from global warming, most of which are harmful.

Direct

There will be an increase in mortality from heat stress, particularly in cities already liable to excessive temperatures. Thus three heat waves in Los Angeles, with temperatures around 41°C, resulted in a peak death rate of 172% of that expected at all ages, those over 85 being most at risk.⁴ Urban populations in developing countries are especially vulnerable because of poor housing conditions and lack of air conditioning. In the United Kingdom this increase in heat related deaths is likely to be more than offset by a decrease in cold related deaths, such those from coronary artery thrombosis.⁵

Indirect

There will be a striking increase in the incidence of a variety of infectious diseases. Gastrointestinal infections by a whole range of organisms, including bacteria that cause typhoid and cholera, are more common in hotter weather, with clinical consequences ranging from mild stomach upset to rapidly fatal gastroenteritis and septicaemia.

Many of the world's major infectious diseases are caused by parasites or viruses that are transmitted by carriers, so called vectors. For example, insects transmit conditions such as malaria, dengue, and yellow fever. The proliferation of many of these vectors is heat and humidity sensitive, so an increase in one or both will cause a larger proportion of the population to be at risk of the condition. Computer models predict the proportion of the world's population potentially at risk from malaria will increase from 45% to 60% later this century.⁶ The reintroduction of endemic malaria into former malaria affected areas of the developed world, such as southern Europe, seems unlikely because of counter measures that can be taken, such as destruction of breeding sites by drainage, change of rate of water flow, and other procedures and the use of insecticides and of chemicals and fish that destroy the larvae. However, the impact on countries that could not take such measures would be devastating as can be judged from the fact that, currently, some 300 to 500 million people are infected with the condition from which two million (mainly young children) die each year.

Climate change is predicted to increase food production at high and mid-latitudes with decreases occurring at lower latitudes. Food production will be reduced in the arid and subhumid tropics, where there are regions which are currently barely able to feed their populations due to high temperature, pests, and lack of water. One climate change scenario in Africa has predicted that that there will be an additional 55 to 65 million people at risk of hunger by the 2080s.⁷ The number of people affected by water shortages, currently about 1.7 billion, is also expected to rise sharply.

A mean sea level rise of 9-88 cm is predicted by 2100 due to thermal expansion of the oceans and melting of ice packs.³ This would cause submergence of low lying islands and a greatly increased risk of flooding in areas already prone (such as Bangladesh) with an approximate doubling of the number of people who already experience flooding, currently about 46 million. In Britain, the east coast, particularly the area between the Humber and the Thames, is at greatest risk of flooding from the sea.⁵

A potential consequence of global warming is an effect on the Gulf Stream, from slowing currents in the North Atlantic a phenomenon that has already been detected.⁸ The Gulf Stream has been calculated to deliver 27 000 times more heat than all Britain's power stations could supply. If the Gulf Stream were to be turned off, winter temperatures in Britain could fall by an average of 11°C, reaching levels found within the Arctic Circle.

Global warming will markedly increase the risk of extreme weather events which many parts of the world are already experiencing. Thus there were about 200 floods, storms, landslides,and droughts a year before 1996, which rose to 392 in 2000.⁹ As well as immediate casualties, such disasters have indirect health effects resulting from loss of shelter, population displacement, and water contamination.

Effects on wildlife

Numerous changes in wildlife have been documented that would be compatible with effects of global warming. For example, nesting dates of many kinds of bird occur earlier and several species of butterflies and birds have shifted their distribution northward and up mountain slopes.¹⁰ Some types of wildlife may not be able to adapt to the new weather conditions fast enough and there is a risk of species becoming extinct.

Action to reduce global warming

The atmosphere can absorb approximately 12 billion tons of CO₂ a year so that, with the current world population of six billion, every individual should produce only two tons a year if the CO₂ level is to remain in equilibrium and allow for sustainable development. In fact 10 tons a year are produced by individuals living in many countries of the European Union and 18 tons by those living in the United States. These figures are often symbolised as footprints of an individual's impact on the environment. Individuals from industrial countries clearly have footprints for energy consumption that are much too large.

Road transport, domestic usage, and industry each account for about a quarter of Britain's CO₂ output,¹¹ so its reduction depends on personal decisions on life style as well as political ones. The former include reduction of car use--walking, cycling, or using public transport instead--improving home insulation and, when possible, buying foods produced locally rather than those brought from afar whose transport, usually by heavy goods vehicle, incurs a large consumption of energy ("food miles"). Political measures include promoting research and investment in renewable forms of energy, such as wind and solar power, with more emphasis on switching from carbon fuels to renewable sources, and measures to reduce road traffic. As consumers and voters we all have considerable ability and responsibility to shape the future political agenda.

In the first international agreement of its kind, the Kyoto Protocol of 1997 committed industrialised nations to reduce GHG emissions by 2010 by an average of 5.2% compared with 1990 levels. Although scientists urge that CO₂ emissions should be cut back to at least 60% of 1990 levels by 2050, even these relatively modest targets have come under attack, primarily from the United States. Sadly, at the recent Bonn conference, the Kyoto targets were further diluted by industrialised countries accepting the sale of "carbon credits" to those countries unable to achieve their target GHG reductions, and by allowing "sinks" so that countries can include carbon absorbed in forests and agricultural land towards their targets.

Health effects of reduction of overconsumption

Reduction of GHG emissions would result in huge health benefits quite apart from avoiding the consequences of global warming. The circumstances that give rise to excessive GHG emissions in the first place, in particular overconsumption of energy and physical inactivity (especially due to the use of the car), play a major role in the epidemic of conditions such as coronary heart disease, obesity, and Type 2 (non-insulin dependent) diabetes that affect these communities.² It is unrealistic to think that populations of industrialised countries can revert to rural ways of living but, nevertheless, there is much that can be done to encourage more physical activity and less consumption of food and fuel. It would be particularly appropriate for healthcare professionals to take a lead in adopting such lifestyles that would not only be healthier for the individual, but crucial for the health of the planet.

Martin Hartog, retired physician, Medact, London
Email: mikerowson@medact.org


studentBMJ 2001;09:399-442 November ISSN 0966-6494

1. Stott R. Carson's syndrome: a major threat to the public's health in the twenty-first century. Medicine Conflict and Survival 2000;16:94-103.
2. Carson R. Silent spring. London:Penguin Books, 1999.
3. Intergovernmental Panel on Climate Change. Climate change 2001: scientific basis. Cambridge: Cambridge University Press, 2001.
4. Occhsli IW, Buckley RW. Excess mortality associated with three Los Angeles September hot spells. Environmental Research 1970;3:277.
5. Department of Health. Health effects of climate change in the UK. London:Department of Health, 2001.
6. Martens WJM, Niessen W, Rotmans J, Jetten TH, McMichael AJ. Potential impact of global climate change on malaria risk. Environmental Health Perspectives 1995;103:458-64.
7. Parry ML, Rosenzweig C. Climate change and world food security: a new assessment. Global Environmental Change 1999, S51-S67.
8. Hansen B, Turrell WR, Osterhus S. Decreasing overflow from the Nordic seas into the Atlantic Ocean through the Faroe Bank since 1950. Nature 2001; 411: 927-29.
9. International Federation of Red Cross and Red Crescent Societies. World Disasters Report 2000. London: Central Books, 2000.
10. Royal Society for the Protection of Birds, English Nature, World Conservation Monitoring Centre, and ERM. No place to go? The impact of climate change on wildlife. London: RSPB, English Nature, World Conservation Monitoring Centre, 1999.
11. May R. Climate change. London: Office of Science and Technology, 1997.