Health and Pollution : Glossary

There are 75 documents in this section.

  • Vector

    22 August 2000

    Organism that acts as an essential intermediate host or definite host for a human pathogen and that plays an active role in its transmission; for example, Anpheles species are vectors of malaria. This definition excludes mechanical carriers or infective materials (such as houseflies and cockroaches), strictly passive intermediate hosts (such as the snail hosts of schistosomiasis) and reservoir species (such as foxes in the case of rabies).

  • Water-washed diseases

    22 August 2000

    Diseases spread from one person to another due to inadequate supplies of water for personal hygiene. These include infections of the skin and eyes (e.g. trachoma) and infections carried by lice, e.g. louse-borne epidemic typhus.

  • Waste

    22 August 2000

    Any material, solid, liquid or gas, that is no longer required by the organism or system that has been using it or producing it. Population growth, new lifestyles and a rapidly changing technology have contributed to an increase in the generation of waste and created serious waste disposal problems.

  • WHO (World Health Organisation)

    22 August 2000

    A UN agency created in 1948 to deal with global health issues and to achieve as high a level of physical, mental and social well-being as possible for peoples of the world. It is involved in a variety of environemental studies, including the impact of climate change and ozone depletion on health, in conjunction with other agencies such as the World Meteorological Organisation (WMO) and the United Nations Environment Program(UNEP).

  • Algal bloom

    21 August 2000

    Abnormally increased biomass of algae in a lake or river. Algal blooms occur naturally in spring and early summer, when the rate of reproduction of the algae outstrips that of their consumers. However, the most serious algal blooms are associated with human activities. Phosphates and nitrates carried into waterways in sewage, agricultural fertilisers and detergents, provide the nutrients that cause explosive growth in the algae population.

  • Arsenic

    21 August 2000

    A highly toxic element which exists in three forms - grey, black and yellow arsenic. It occurs naturally in the environment, being released from arsenic-bearing rocks through weathering. Arsenic accumulates in the environment so that small doses, relatively harmless individually, may eventually kill organisms - including people.

  • Bioaccumulation

    21 August 2000

    The retention of non-biodegradable chemicals, or those that decay only slowly, in the bodies of organisms. Toxic metals such as lead (Pb) and mercury (Hg) and pesticides such as DDT are absorbed more rapidly than they are excreted and therefore accumulate in the body. Accumulation often takes place in specific locations, including bones, fatty tissues and organs, such as liver and kidney. The impact of bioaccumulation varies with the chemical and the organism involved, but it can cause death, prevent reproduction or increase susceptibility to disease.

  • CFC's (Chlorofluorocarbons)

    21 August 2000

    A group of chemicals containing chlorine (Cl), fluorine (F) and carbon (C), sometimes referred to by their trade name Freon. These synthetic compounds were used extensively for refrigeration and aerosol sprays until it was realized that they destroy ozone (they are also very powerful greenhouse gases) and have a very long lifetime once in the atmosphere (more than 100 years). The Montreal Protocol agreement of 1987 has resulted in the scaling down of CFC production and use in industrialised countries.

  • Cholera

    21 August 2000

    A bacterial disease caused by drinking water contaminated by sewage or eating food that has not been washed or is inadequately cooked. It is common in areas where the growth in population has outstripped the development of facilities for providing clean water or disposing of sewage. The problem is most severe in warm climates where high temperatures encourage the growth of the cholera bacteria.

  • Carcinogen

    21 August 2000

    A chemical or physical agent capable of causing cancer. Human activities can introduce chemical carcinogens such as chlorinated hydrocarbons or physical carcinogens such as asbestos or ionising radiation into the environment, but natural carcinogens such as toxic metals beryllium (Be), cadmium (Cd) and selenium (Se) are also present. There are two types of carcinogens: DNA-reactive carcinogens that alter the DNA of cells, and epigenetic carcinogens that do not react with DNA but may alter the immune system, cause hormonal imbalances or cause chronic tissue injury, all of which could lead to cancer. Carcinogens may be inhaled, ingested or absorbed through the skin.