UPSC Express

Major Air Pollutants

Particulate matter (PM):

• PM affects more people than any other pollutant.
• The major components of PM are sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water.
• It consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air.
• The most health-damaging particles are those with a diameter of 10 microns or less, (≤ PM10), which can penetrate and lodge deep inside the lungs.
• Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as of lung cancer.
  • Health effects:
• There is a close, quantitative relationship between exposure to high concentrations of small particulates (PM10 and PM2.5) and increased mortality or morbidity, both daily and over time.
• Small particulate pollution have health impacts even at very low concentrations – indeed no threshold has been identified below which no damage to health is observed.

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Ozone (O3):

• Ozone at ground level – not to be confused with the ozone layer in the upper atmosphere – is one of the major constituents of photochemical smog.
• It is formed by the reaction with sunlight (photochemical reaction) of pollutants such as nitrogen oxides (NOx) from vehicle and industry emissions and volatile organic compounds (VOCs) emitted by vehicles, solvents and industry.
• As a result, the highest levels of ozone pollution occur during periods of sunny weather.
  • Health effects:
• Excessive ozone in the air can have a marked effect on human health.
• It can cause breathing problems, trigger asthma, reduce lung function and cause lung diseases.

Nitrogen dioxide (NO2): 

• As an air pollutant, NO2 has several correlated activities.
• At short-term concentrations exceeding 200 μg/m3, it is a toxic gas which causes significant inflammation of the airways.
• NO2 is the main source of nitrate aerosols, which form an important fraction of PM2.5 and, in the presence of ultraviolet light, of ozone.
• The major sources of anthropogenic emissions of NO2 are combustion processes (heating, power generation, and engines in vehicles and ships).
  • Health effects:
• Epidemiological studies have shown that symptoms of bronchitis in asthmatic children increase in association with long-term exposure to NO2.
• Reduced lung function growth is also linked to NO2.

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Sulfur dioxide (SO2):

• SO2 is a colourless gas with a sharp odour.
• It is produced from the burning of fossil fuels (coal and oil) and the smelting of mineral ores that contain sulfur.
• The main anthropogenic source of SO2 is the burning of sulfur-containing fossil fuels for domestic heating, power generation and motor vehicles.
  • Health effects:
• SO2 can affect the respiratory system and the functions of the lungs, and causes irritation of the eyes.
• Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis and makes people more prone to infections of the respiratory tract.
• Hospital admissions for cardiac disease and mortality increase on days with higher SO2 levels.
• When SO2 combines with water, it forms sulfuric acid; this is the main component of acid rain which is a cause of deforestation.

Carbon monoxide: 

• It comes from the burning of fossil fuels, mostly in cars. It cannot be seen or smelled.
  • Health effects:
• Carbon monoxide makes it hard for body parts to get the oxygen they need to run correctly.
• Exposure to carbon monoxide makes people feel dizzy and tired and gives them headaches.
• In high concentrations it is fatal.
• Elderly people with heart disease are hospitalized more often when they are exposed to higher amounts of carbon monoxide.

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