STRUCTURE

• Introduction – What is pollution (15 words)                     
• Body – Explain
  • What are the primary and secondary air pollutants (120 words)
  • human health problems caused by air pollution (60 words)
  • note on air pollution in New Delhi (60 words)
• Conclusion – Mention a short conclusion  (15 words)

ANSWER

Pollution is the introduction of contaminants into the natural environment that cause adverse change. Air pollution is defined as the introduction of pollutants, organic molecules, or other unsafe materials into Earth’s atmosphere.

Air borne emissions emitted from various industries are a cause of major concern. These emissions are of two forms, viz. solid particles (SPM) and gaseous emissions. Thus, Air Pollutants can be solid particles, liquid droplets, or gases. They can be natural or manmade. The pollutants have been classified into primary and secondary categories.

• The primary pollutants are “directly” emitted from the processes such as fossil fuel consumption, Volcanic eruption and factories. The major primary pollutants are Oxides of Sulphur, Oxides of Nitrogen, Oxides of Carbon, Particulate Matter, Methane, Ammonia, Chlorofluorocarbons, Toxic metals etc.
• The secondary pollutants are not emitted directly. The secondary pollutants form when the primary pollutants react with themselves or other components of the atmosphere. Most important secondary level Air Pollutants are Ground Level Ozone, Smog and POPs (Persistent Organic Pollutants).

PRIMARY AIR POLLUTANTS

Oxides of Sulphur: Sulphur Oxides are generally a product of the Volcanoes, Industrial processes, Coal and petroleum, because most of them have Sulphur as a component. The Sulphur Dioxide in presence of a catalyst such as NO2 causes Acid Rain, because of the formation of Sulphuric Acid. The Indian Coal is though low in sulphur content but still coal consumption is a major danger of acid rain because of the coal based power plants.

Oxides of Nitrogen: Most of the Nitrogen Oxides are produced due to high temperature combustion. In the cities the brown haze dome above the cities is mostly because of the Nitrogen Oxides. The most important toxic gas is Nitrogen dioxide which is brown, with sharp odour.

Oxides of Carbon

• Carbon Monoxide, which is colourless, odourless and non irritating but very poisonous gas is the product of incomplete combustion of the natural gas, coal or wood. The vehicle exhaust is the major source of CO.
• The Carbon Dioxide is associated with the Ocean Acidification and is emitted from combustion, factories and respiration of living organisms.
• Then, we have primary pollutants such as Volatile Organic Compounds or VOCs which are methane (CH4) and non-methane (NMVOCs).
• Methane is a GHG which contributes to Global Warming.
• The NMVOCs include the aromatic compounds such as Benzene, Toluene, Xylene which are proved or suspected carcinogens.
• Another dangerous compound is the 1,3-butadiene, often associated with industrial uses.

Particulate Matter: The particulate matters are the fine particles which may be either solid or liquid, suspended in a gas. They are different from the Aerosols. Aerosols are particle and gas referred together. The aerosols which are created by the Human activities are anthropogenic aerosols. They account for around 10% of the total aerosols in the atmosphere.

Other Primary Pollutants: Another category of the primary air pollutants is toxic metals such as Cadmium, Lead and Copper, which are products of the Industrial processes. The Chlorofluorocarbons (CFCs) are proved to be harmful to the ozone layer emitted from products currently banned from use. In agriculture process, Ammonia is emitted which has characteristic pungent odor. It is a precursor to foodstuffs and fertilizers. Ammonia is also a building block for the synthesis of many pharmaceuticals.

SECONDARY AIR POLLUTANTS

Ground Level Ozone: The most important secondary pollutant is the Ground Level Ozone or Tropospheric Ozone. Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapours, and chemical solvents are some of the major sources of Nox and VOC. Ground Level Ozone forms due to reactions of the NOx, Carbon Monoxide and VOCs in presence of sunlight.

Smog: Another most important secondary pollutant is the Smog, which has made up of Smoke and Fog. Traditionally, the smog has resulted from large amounts of coal burning in an area caused by a mixture of smoke and sulphur dioxide. Now-a-days, the Vehicle emissions and Industrial emissions that are acted on in the atmosphere by ultraviolet light from the sun to form secondary pollutants that also combine with the primary emissions to form photochemical smog.

HUMAN HEALTH PROBLEMS CAUSED BY AIR POLLUTION

• Exposure to air pollution is associated with numerous effects on human health, including pulmonary, cardiac, vascular, and neurological impairments. Air pollution is found to cause low birth weight in children, tuberculosis, asthma, ischemic heart disease, nasopharyngeal and laryngeal cancers, cataracts, etc.
• The health effects vary greatly from person to person.
• High-risk groups such as the elderly, infants, pregnant women, and sufferers from chronic heart and lung diseases are more susceptible to air pollution.
• Children are at greater risk because they are generally more active outdoors and their lungs are still developing. Exposure to air pollution can cause both acute (short-term) and chronic (long-term) health effects.
• According to some research, air pollution can also impair cognitive development.
• Air pollution is associated with infections & diseases that kill around 600,000 children under five years of age every year.
• Several studies reveal a higher prevalence of symptoms of chronic bronchitis in areas with higher particulate air pollution.

AIR POLLUTION IN DELHI

The severe air pollution that affects life is not restricted to Delhi but to a huge airshed around it that includes the NCR. This encompasses Gurgaon, Faridabad, Ghaziabad, Noida, places in Haryana, UP, and even Alwar (Rajasthan).

The most important causes of air pollution in Delhi and adjoining areas are as follows:

• Increasing population and related developmental activities at the cost of environmental damage.
• The development of the region has largely been unplanned and often, industrial units that spew harmful chemicals into the atmosphere are located in residential and commercial areas and not designated areas.
• Increased vehicular traffic (which has not come down despite the Delhi metro) and the consequent rise in air and noise pollution.
• Almost 8,000 m tonnes of solid waste is being generated in Delhi (National Environmental Engineering Research Institute) every day, however, the authorities manage to clear only about 5000 – 5500 m tonnes of waste daily. This adds to the garbage piling up. This is not counting the hazardous and non-hazardous waste from industries.
• There is a rather high dependence on fossil fuels whose burning causes a lot of emission of harmful gases into the atmosphere.
• Large scale construction activities lead to increased dust pollution which leads to around 56% of PM10 and the PM2.5 load.
• The landlocked geography of Delhi also causes more air pollution as compared to other cities. The northwesterly winds coming from Rajasthan, sometimes Pakistan and Afghanistan bring in dust to the region. The Himalayas obstruct the escape route of the air. This causes the dust and pollutants to settle in the region. This is more prominent during the winters because of low-level inversion (upward movement of air from the layers below is stopped). It is because of this landlocked geography of Delhi that it faces greater pollution when compared to the coastal city of Chennai (where despite high automobile population, has the sea breeze which provides an effective entry and exit for dispersing pollutants).
• Stubble burning also contributes to the air pollution in the region. During the winter months, the large scale stubble burning practised in Punjab, Haryana and Rajasthan cause a thick blanket of smog to cover Delhi-NCR. According to a study, the burning of crop residue released about 149 million tonnes of carbon dioxide, more than 9 million tonnes of carbon monoxide, 0.25 million tonnes of oxides of sulphur (SOX), 1.28 million tonnes of particulate matter (PM) and 0.07 million tonnes of black carbon. As evident, it contributes to a lot of greenhouse gas emissions.
• Firecrackers, although not the top reason for air pollution, also contributes to the problem.