Primary and Secondary Pollutants

Posted on Oct 26 2017 - 12:04pm by simplinotesadmin


  • Hydrocarbons at high concentrations are carcinogenic and therefore harmful for the lungs.
  • Aromatic hydrocarbons like benzene and toluene are more dangerous, inhalation of their vapour causes irritation of the mucuous membrane. Increased concentration of hydrocarbons vapours increases mucus irritation leading to blockage of the respiratory tract, as a result of which a person coughs continuously.
  • Hydrocarbons react with nitrogen oxides and produce photochemical smog that caused irritation to the eyes, nose and throat, as well as repiratory distress.
  • Plants exposed to high levels of hydrocarbons display yellowing of the leaves.

v. Particulates
These are small, solid particles and liquid droplets present in the atmosphere in fairly large numbers and sometimes pose serious air pollution problem. In size particulates ranges from 0.02 µ in diameter of 500 µ with lifetime varying from a few seconds to several months.

  • The particulates can be organic or inorganic in nature.
  • The natural particulate matter present in aerosol is known as organic particulate matter. For example, particulates that originate from volcanoes, dust storms, forest and grassland fires and living vegetation.
  • Inorganic particulate matter mainly comprised, metal oxides formed during the burning of fossil fuels, industrial processes, vehicular exhaust and acid rain. During combustion of pyrites, coal iron oxide is formed and from its ash, calcium oxide is released into the atmosphere.


  • Particle pollution exposure to a variety of health issues, including irritation of the eyes, nose and throat, coughing, chest tightness and shortness of breath, reduced lung function, irregular heartbeat, asthma attacks, heart attacks, premature death in people with heart or lung disease.
  • Particulate matter adversely affects the plant kingdom. The deposition of toxic substances makes the soil unsuitable for plant growth. These particles also get deposited on plant leaves and block the stomata of the plant, thereby decreasing the rate of  respiration and photosynthesis causing the vegetation to perish.
  • The suspended particulate mater accelerates the corrosion of metals, It is more common in urban and industrial areas than in villages.
  • They also corrode buildings and sculptures.
    Particulates educec visibility by adsorbing and effectively scattering solar radiation.
    They influence the climate through formation of clouds, rain and snow and acts as nuclei on which water condenses. Hence it also affects the nature of precipitation.


ii. Secondary Pollutants

Secondary pollutants are formed by primary pollutants their reaction with normal atmospheric compounds. Ozone is a secondary pollutant formed by photochemical reaction between primary pollutants and natural atmospheric gas. Ozone affects the respiratory and nervous system. It also damages rubber products and textiles. PAN, a secondary pollutant is formed when hydrocarbon radicals react with nitrogen dioxide. Peroxy Acetyl Nitrate causes photochemical smog and also causes irritation of the eyes, nose, throat and respiratory distress. Disposition of the toxic secondary pollutants, either in gaseous form or as particulates on soil make the soil unsuitable for plant growth. Acid rain for longer period decreases the pH of the soil and makes it acidic. Particulates on the other hand, deposit on the leaves of plants and block their stomata. As a result the rate of photosynthesis and transportation decreases and leads to decreased crop yield and retarded growth. Cattle are also found to be affected by air pollution. Ozone and PAN irritates the eyes, impair vision and create breathing problems leading to asthma in human beings.

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