There are a number of air pollutants that are released into the atmosphere.
1. Carbon dioxide and carbon monoxide:
Carbon oxides are one of the largest groups of pollutants, causing widespread global harm. These harmful gases are emitted from vehicles, industrial furnaces and other engines. When fossil fuels are not burnt properly, they result in emission of carbon monoxide, a colourless and odourless poisonous gas. Normal combustion or burning causes the release of carbon dioxide. Carbon dioxide is said to be the main cause of the greenhouse effect.
Deforestation is a major cause of rise in pollution levels because of carbon dioxide. Forests have the ability to absorb the carbon dioxide levels in the air and therefore decrease air pollution.
Sources that contribute to carbon monoxide production include marsh gas production and volcanic eruptions in nature, human activities like use of motor vehicles, industrial emissions and burning of agricultural remains.
2. Sulphur dioxide:
Possibly one of the most harmful of gases, sulphur dioxide is converted into sulphuric acid in the atmosphere when it rains and is deposited on our surrounding environments with the rainwater. This is known as acid rain. These gases are released from factories and electric power plants that make use of coals and fuel oils that contain sulphur. Metallurgic ores are also a cause of sulphur dioxide emissions.
Burning of fossil fuels, volcanic eruptions, industrial emissions, power plants and gases released from motor vehicles result in increase in sulphur dioxide.
i. The respiratory system gets affected and results in cough and asthma.
It damages vegetation like crops and development of plants.
iii. It contaminates water. Sulphuric oxides turn into sulphuric acid on reaction with water.
iv. It causes allergies like irritation in the eyes.
v. It causes leaf necrosis.
3. Nitrogen oxide:
Nitrogen oxide is a brown gas that is released on combustion of fossil fuels by automobile engines, industrial plants, power plants and burning of biomass. It is a poisonous gas which is produced wherever combustion takes place. Nitric oxide (NO) is colourless and odourless while nitrogen dioxide (NO,) has a strong smell. These gases result in smog and cause the greenhouse effect. Deforestation and nitrogen based-fertilizers also cause an increase in nitrogen dioxide.
i. Nitrogen dioxide spoils the leaves of plants and curbs photosynthetic processes.
ii. Leaves are not able to produce chlorophyll and results in chlorosis.
iii. It causes fluid formation in lungs and shortness of breath.
iv. It causes nausea.
v. It results in respiratory problems like bronchitis.
vi. It causes digestive problems.
Generated by vehicles and by decomposition of organic matter, hydrocarbons are produced due to incomplete combustion of burnt fuel. Hydrocarbons are a cause of smog that has become prevalent in the cities. Apart from pollution, smog also causes accidents because of the lack of visibility. The most prominent hydrocarbon in air is methane (CH4).
Pollution due to vehicles, industrial activities, gasoline, and bacterial activity on organic matter causes a rise in hydrocarbons in the air.
i. Aromatic hydrocarbons are carcinogenic and can cause lung and skin cancer in human beings.
ii. Abdominal pain and vomiting in human beings.
iii. Euphoria followed by lethargy and headache.
iv. Causes photochemical smog which results in irritation of the eye and respiratory system.
Smog is caused due to incomplete combustion of fossil fuels, and is a smoky mixture of carbon monoxide and organic compounds. It is found more in cities rather than in rural areas, particularly during winters, as a lot of it is caused due to vehicular traffic. Smog is a major hazard, because it reacts with oxygen in the atmosphere to form sulphuric acid and other organic acids, which then condense and reach the earth’s surface as droplets.
i. Acid rain that is caused due to sulphuric acid in the atmosphere damages plant life, freshwater life in lakes and soil fertility.
ii. Smog causes breathing problems in humans.
iii. It reduces visibility which causes delays in road, rail and air traffic.
6. Particulate matter:
Tiny solid and liquid particles in the air, like smoke, dust, and soot, make up particulate matter which pollutes air. These particles contain harmful substances like asbestos, fluorides, lead and mercury. They can come from many sources including smelting operations, fly ash plants, forest fires, fossil fuels, industrial activities, construction and transportation.
Suspended particulate matter or SPM are fine particles less than 10 micrometres. They affect our respiratory tract. Residual Suspended Particulate Matter (RSPM) are fine particles, less than 4-5 micrometres. They enter our respiratory system and damage lungs.
i. It causes asthma, bronchitis and lung cancer in human beings.
ii. Result in cardiovascular problems
iii. Respiratory problems for animals
iv. May cause heart disease
v. Dust particles reduce visibility
vi. It causes storms and formation of clouds.
vii. SPM corrodes metals, monuments, buildings and sculpture.
viii. Chokes stomatal pores, coats leaf surfaces and reduces rate of transpiration and photosynthesis
Chlorofluorocarbons or CFCs are synthetic substances that emanate out of industries and from aerosols. They are very light and can reach the second layer of the atmosphere, called the stratosphere. Stratosphere contains ozone which is a life saving gas because it absorbs the harmful ultraviolet radiation from the sun.
However, CFCs lower the ozone level in the stratosphere. Therefore, CFCs contribute to the greenhouse effect and result in global warming. The major source of chlorofluorocarbons is freon from old air conditioners and refrigerators.
i. Increased levels of sun’s ultraviolet radiations can reach earth.
ii. Causes skin cancer.
iii. Causes decrease in human immune system.
iv. Causes harm to terrestrial and aquatic life forms.
Radon is a radioactive gas that is formed in nature. It is particularly harmful in places that are not properly ventilated.
Mining, underground wastes, power plants, and constructions are some of the sources of radon.
i. Causes lung cancer.
ii. Gives rise to respiratory problems.