Health and Pollution : Glossary

There are 75 documents in this section.

  • DDT (Dichlorodiphenyl-trichloroethane)

    21 August 2000

    A chlorinated hydrocarbon once widely used as a broad-spectrum insecticide. Introduced during the Second World War as a delousing agent, it proved very effective against diseases such as malaria, yellow fever and typhus, which were spread by insects. Over the longer term, serious side affects became apparent. Being a broad-spectrum product, it killed beneficial insects as well pests and could accumulate in the environment for perhaps 20 years. Although not soluable in water, it was soluable in fat, which allowed it to migrate up the food chain, where it accumulated in the body tissue of the predators. In birds it caused the thinning of eggshells, seriously reducing the breeding success of some species. By the mid-1960s, DDT was found to be widespread in the fatty tissue of the human population, passed on from mother to child through breast milk. Although the link between DDT concentration and human health was not clear, its potential to cause serious ecological disruption was recognised, and it was eventually banned or had its use severely restricted in the developed world.

  • Dioxins

    21 August 2000

    A group of approximately 75 chlorinated hydrocarbons formed as by-products of chemical reactions involving chlorine (Cl) and hydrocarbons. Dioxins appear as manufacturing impurities in some herbicides, wood preservatives and disinfectants, and are released into the environment during the incineration of chlorine-based plastics or as a result of the chlorine bleaching process in the pulp and paper mills. They are also released in industrial processes such as steel making. Dioxins are persistent chemicals, accumulating in soil and human fatty tissue. Health effects are varied and complex, ranging from skin problems, such as chloracne, to cancers, birth defects and serious immunology, neurological and behavioural problems.

  • Ecological balance

    21 August 2000

    Stability in an ecosystem achieved through the development of equilibrium among its various components. This does not imply that the community is static. It is subject to natural variations associated with ecological succession and other influences such as fire, disease and climate change, but the system is normally sufficiently elastic to make the necessary adjustments without major displacement of the balance. Human intervention that includes the introduction or removal of plants and animals, pollution of the environment and destruction of habitat is now a main cause of imbalance in many ecosystems.

  • El Niño/Southern Oscillation (ENSO)

    21 August 2000

    El Niño is the name originally given by local inhabitants to a weak warm ocean current flowing along the coast of Ecuador and Peru. ENSO is an extensive, intense, atmospheric and oceanic phenomenon affecting the tropical Pacific Ocean. It is associated with major anomalies in atmospheric circulation and rainfall patterns. El Niño occurs irregularly, but approximately every four years on average. ENSO events have impacts on fisheries, bird life and mainland weather.

  • Emerging infectious disease

    21 August 2000

    Disease that is new in the population or rapidly increasing in incidence or expanding in geographical range.