Air Pollution

Air pollution refers to the introduction of harmful substances into the atmosphere. Various human activities release pollutants into the air. Some of the major pollutants in our atmosphere include:

  • Sulphur oxides: These are chemical compounds of sulphur and oxygen. Of these, sulphur dioxide is of particular concern. The burning of coal and petroleum causes sulphur dioxide to be released into the atmosphere. It may react with nitrogen oxide and water molecules in the air to produce acid rain. Acid rain refers to rain (or any other form of precipitation) which is unusually acidic because of pollution. Acid rain can affect plants by slowing their growth or killing them. In some countries, such as Germany and Poland,  large areas of forest have been damaged. Buildings, statues and vehicles can be corroded. Acid rain can also affect water bodies such as lakes, harming or killing the creatures which live in them.
  • Nitrogen oxides: These are chemical compounds of nitrogen and oxygen. The high temperature combustion (burning) of coal and petroleum produces nitrogen oxides. Nitrogen dioxide in the atmosphere contributes to the formation of acid rain. Nitrogen dioxide can irritate the lungs and lead to an increase in respiratory illness especially in children. Nitrogen oxides in the atmosphere also contribute to the formation of ground level ozone.
  • Carbon monoxide: This is a poisonous gas formed as a result of the incomplete combustion of fuels such as coal, petroleum, natural gas or wood. It reduces the body’s ability to carry oxygen to the organs and tissues of the body. Vehicle exhaust is a major source of carbon monoxide.
  • Particulates: This refers to tiny solid or liquid particles found in the air. They include dust, smoke, soot, metals, acids and organic chemicals. Some of these particles are released into the atmosphere from quarries, construction sites, unpaved roads and factories. Others form in the atmosphere as a result of the reaction of chemicals such as sulphur dioxide and nitrogen oxides. Some particles are so tiny that they can be inhaled deep into the lungs causing health problems. These health problems include difficulty breathing and decreased lung function. Particulates can also aggravate existing  conditions such as asthma and lung disease. Particles in the atmosphere can also reduce visibility.
  • Chlorofluorocarbons (CFC’s): These are chemicals which contain atoms of chlorine, fluorine and carbon (hence the name). CFC’s were once commonly used in refrigerants and aerosols. They are not toxic or flammable but they are harmful to the environment. About 20km – 40km above the Earth’s surface, there are high concentrations of ozone (O3). This ozone layer protects us by absorbing much of the Sun’s harmful radiation. When CFC’s are released into the air, they may rise high into the atmosphere where they destroy ozone molecules, thereby depleting our ozone layer.
  • Ground level ozone:  While the ozone layer protects us from harmful solar radiation, near ground level, ozone acts as a pollutant. This  pollutant forms in the lower atmosphere as a result of a chemical reaction between nitrogen oxides and other pollutants known as volatile organic compounds. This chemical reaction is caused by sunlight. Inhaling ozone can cause a variety of health issues including chest pain, congestion, coughing and reduced lung function. It can cause conditions like asthma, bronchitis and emphysema to worsen.Ground level ozone (also called bad ozone) is a major component of smog. Smog is a type of pollution which can form when ground level ozone mixes with other pollutants in the air. Smog can be described as a low cloud of pollutants and it can be observed hovering over many of the world’s developed cities.


This photo was taken in New York in1988. A thick blanket of smog can be seen over the city.

This photo was taken in New York in 1988. A thick blanket of smog can be seen over the city.

Watch the video below which shows the effects of air pollution

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