Health and Pollution : Glossary

There are 75 documents in this section.

  • Eutrophication

    22 August 2000

    The occurrence of high nutrient levels in freshwater and marine ecosystems, usually resulting in excessive plant growth and the death of animal and some plant life due to oxygen deprivation.

  • Fossil fuels

    22 August 2000

    Fuels such as coal, oil and gas made by decomposition of ancient animal and plant remains which give of carbon dioxide when burned.

  • Global warming

    22 August 2000

    The idea that increased greenhouse gases cause the Earth's temperature to rise globally.

  • Greenhouse effect

    22 August 2000

    The cause of global warming. Incoming solar radiation is transmitted by the atmosphere to the Earth's surface, which it warms. The energy is retransmitted as thermal radiation, but some of it is absorbed by molecules of greenhouse gases instead of being retransmitted out to space, causing the temperature of the atmosphere to rise. The name comes from the ability of greenhouse glass to transmit incoming solar radiation but retain some of the outgoing thermal radiation to warm the interior of the greenhouse. The 'natural' greenhouse effect is due to the greenhouse gases present for natural reasons, and is also observed for the neighbouring planets in the solar system. The 'enhanced' greenhouse effect is the added effect caused by the greenhouse gases present in the atmosphere due to human activities, such as burning of fossil fuels and deforestation.

  • Greenhouse gases

    22 August 2000

    Molecules in the Earth's atmosphere such a carbon dioxide (CO2), methane (CH4) and CFCs which warm the atmosphere because they absorb some of the thermal radiation emitted from the earth's surface.

  • Hantavirus

    22 August 2000

    Type of virus; some hantaviruses are pathogenic to humans, causing severe illness. Rodents are a natural reservoir of all hantaviruses. Infection in humans occurs via inhalation or ingestion of materials contaminated with rodent excreta, although a tick vector may be involved.

  • Organochlorides

    22 August 2000

    A group of organic compounds that contain chlorine (Cl). They have a variety of forms and uses including aerosol propellants, plasticisers, transformer coolants (PCBs) and food packaging (PCVs), but their greatest use was as pesticides, in the form of DDT, Aldrine and Lindane. However, with time many pests have developed immunity to them and it has also become clear that the characteristics that made them good pesticides - persistence, mobility and high biological activity - also posed dangers for the environment. Organochlorides accumulate in the fatty tissue of animals, and through biomagnification in the food chain may reach toxic levels in predators. Because of side effects such as sterility, birth defects, cancer and damage to the nervous system, they have been banned or had their use severely restricted in most parts of the world.

  • Organophosphoruus compounds

    22 August 2000

    A group of pesticides that work by blocking the central nervous systems of the organisms exposed to them. Malathion and diazonon are the most commonly used organophosphates. They are highly effective against insects, but break down rapidly in the environment and do not bioaccumulate. For these reasons, they are preferred over organochloride pesticides. Although generally considered safer than the organochlorides, they are highly toxic to humans and other mammals and may be carcinogenic.

  • Ozone hole

    22 August 2000

    A region of the atmosphere over Antarctica where, during spring in the southern hemisphere, about half the atmospheric ozone disappears. The Ozone layer protects the earth's surface from the effects of excess ultraviolet radiation. However, the growth in the volume and use of ozone-destroying chemicals, such as CFCs, has depleted the layer, allowing greater amounts of ultraviolet radiation to pass through to the earth's surface, raising fears of the increased occurrence of skin cancer, eye damage and genetic mutation in terrestrial organisms. (Recently scientists have decreases of 10-20 per cent in ozone over the Arctic).

  • Pandemic

    22 August 2000

    Epidemic occurring over a very wide area, crossing international boundaries and usually effecting large numbers of people.