POLLUTION

As a result of over-population, rapid industrialisation and other human activities, such as agriculture and deforestation, the Earth is becoming loaded with various pollutants released as by-products. Pollution occurs when the environment is contaminated by waste, chemicals and other harmful substances at a rate faster than they can be dispersed, diluted, decomposed, recycled, or stored in some harmless form.

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Pollutants

Pollutants are generally grouped into two classes:

  • Biodegradable pollutants, such as domestic waste products, sewage, agricultural residue, paper, wood, etc., which are broken down by microorganisms;
  • Non-biodegradable pollutants, such as various insecticides and pesticides, mercury, lead, arsenic, aluminium, plastics and radioactive waste, which do not break down into simpler, harmless products.
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Types of pollution

Pollution is broadly classified according to the part of the environment that is affected:

  • Air pollution is the release of chemicals, gas and dust into the atmosphere. Increased quantities of some air pollutants1 affect the weather, contribute to the greenhouse effect, can cause acid rain, persistent smog and damages to the ozone layer1;
  • Water pollution occurs when pollutants are discharged directly or indirectly into lakes, rivers, oceans and groundwater without proper treatment to remove harmful compounds. Water pollution of human origin is classified as:
  • point source (PS), when it enters a waterway from a single, identifiable source, e.g. discharge from a factory;
  • non-point source (NPS), when contamination is from widespread sources, e.g. the leaching out of nitrogen compounds from fertilised agricultural land;
  • Soil pollution is the result of chemicals, pesticides, insecticides, fertilisers, and industrial waste which leach through the soil. The most significant soil contaminants are heavy metals such as cadmium (found in fungicides or fertilisers) and lead (used in batteries and pesticides). Not to mention solid waste which litters roadsides, urban areas, seas, lakes and rivers.

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1 Air pollutants include carbon monoxide, carbon dioxide, sulphur dioxide, chlorofluorocarbons (CFCs) and nitrogen oxides produced by factories and motor vehicles.


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1 What is the ozone layer? Use the net to find information.


Other forms of pollution

Other, more recently defined, forms of pollution which can be as dangerous as traditional ones, are:

  • Light pollution, from overillumination practices, can lead to sleep disorders, depression, diabetes, breast cancer and more;
  • Noise pollution, mostly from roads, aircraft and industry, causes high blood pressure, speech interference, loss of hearing, and disruption of sleep;
  • EMF (electromagnetic field) pollution, from electrical and wireless devices, may have harmful effect on living beings which are still being investigated;
  • Radioactive pollution, from the improper management of radioactive waste from nuclear power plants, can cause genetic mutation, cancer and cardiovascular diseases.
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