We have already studied that there is a balance between biotic and abiotic factors of environment. But human beings are disturbing this balance of nature to fulfil their needs of food, clothing, housing, transport and industry. This environmental imbalance created by is giving rise to a number of problems called environmental problems. Some of environmental problems caused by harmful activities of human beings are:
- Environmental pollution
- Soil erosion
- Green house effect or Global warming
- Depletion of ozone layer
- Formation of salt deserts (salinisation)
- Extinction of species
- Depletion of natural resources
- Waste accumulation
Green House Effect/ Global Warming
Excessive combustion of fuels in homes, motor vehicles and industries, various agricultural activities, decomposition of organic matter and deforestation release a lot of carbon dioxide in atmosphere. The increased amount of carbon dioxide accumulates in atmosphere and absorbs more and more heat radiations reflected by earth. This results an increase in temperature of earth and is called green house effect (or global warming).
Harmful Effects of Green House Effect (or Global Warming)
The green house effect (or global warming) can change the weather of earth. It can also melt the polar ice caps and glaciers. Melting of polar ice caps and glaciers can raise the level of seas. This will result flooding of cities and fertile land situated near sea.
Before discussing acid rain, we should know the meaning of acidic gases. Those gases which combine with water of air to form acids are called acidic gases. Examples of acidic gases are sulphur dioxide gas and oxides of nitrogen. These gases are produced in large quantity during burning of petroleum and coal in industries, thermal power stations, kitchens and vehicles. In the air, sulphur dioxide and oxides of nitrogen dissolve in water vapours to form sulphuric acid and nitric acid respectively. When rain containing sulphuric acid and nitric acid falls on earth, we call it acid rain.
Harmful Effects of Acid Rain
- Acid rain cause many respiratory and skin problems in human beings. It also cause irritation in eyes.
- It cause discolouration and deterioration of buildings, statues and historical monuments made of marble.
- It also damages crops and reduces agricultural productivity.
Depletion of Ozone Layer
Ozone layer is a protective layer present in upper atmosphere. Ozone layer does not allow the harmful ultraviolet rays present in sunlight to enter in the atmosphere of earth. Thus, ozone layer protects us from the harmful effects of ultraviolet rays present in sunlight. But, use of refrigerators, air conditioners, fire extinguishers and aerosol sprayers is releasing chlorofluorocarbons (CFCs) in atmosphere. The chlorofluorocarbons react with ozone of ozone layer and destroy it. This destruction of ozone layer by reacting with chlorofluorocarbons is called depletion of ozone layer or thinning of ozone layer. Due to depletion of ozone layer, ultraviolet rays are reaching the earth and are causing following harmful effects.
- Ultraviolet rays cause damage to the eyes.
- Ultraviolet rays cause skin cancer.
- Ultraviolet rays lower the resistance of body to fight against diseases.
Carbon Monoxide Poisoning
Carbon monoxide is a poisonous gas produced mainly by the incomplete combustion of fossil fuels like coal, petroleum and natural gas in industries, motor vehicles, kitchens etc. A large amount of carbon monoxide in air can cause carbon monoxide poisoning. This happens as follows:
When a person breathe in the air polluted with carbon monoxide, then carbon monoxide easily combines with haemoglobin present in blood and forms a stable compound called carboxyhaemoglobin. Due to formation of this compound, haemoglobin cannot supply oxygen from lungs to different parts of the body. This results in deficiency of oxygen in the body. The deficiency of oxygen in the body causes suffocation, headache, dizziness, unconsciousness and even death.
Lead is a toxic chemical which is produced by combustion of petrol containing tetra-ethyl lead in the motor vehicles. The harmful effects of lead are:
- Lead damages organs like liver, kidney and intestine.
- It interferes with development of red blood cells in the body and thus causes anaemia.
- It causes paralysis of muscles and mental disorders.
Bio-magnification is the accumulation of harmful chemicals in human body through food chains. The main cause of bio-magnification is the use of pesticides such as DDT on crop plants. When such pesticides are sprayed on plants, some of these poisonous chemicals mix up with soil and are absorbed by plants from soil along with water. When human beings use these plants, the poisonous chemical substances go inside their bodies and accumulate there. This process is called bio-magnification.