Deterioration in the natural form of water is caused by mixing unwanted elements more than the specific limit. Use of such water causes various water-borne diseases. Pollutants deforming water enter from different sources on account of human activities and they cause harmful effects on man. Other creatures on earth and in water are also affected by it.
Effects of water pollution can be described from the following view points:
Effects on Man:
Water is a natural gift which has no alternative existing on earth. Hence, water has been termed as life. As per latest surveys, per capita requirement of water is 140 litre.
Man needs water for drinking, cooking, cleaning, irrigation etc., which should be fresh. Polluted water causes the following diseases:
1. Water-borne diseases:
Water polluted by human and animal excreta, if drunk or used otherwise, causes plague, typhoid and other diseases.
2. Diseases caused by contact with water:
Taking bath with polluted water affects eyes and causes skin diseases and diarrhea.
3. Diseases based on water:
Many types of micro organisms exist in polluted water, the use of which spread infectious diseases.
Some disease bearing micro organisms and diseases caused by them are described below:
Infectious diseases like hepatitis, jaundice and polio diseases are caused by virus. About 2000 persons suffered from jaundice due to polluted water in 1978.
Bacteria cause typhoid, paratyphoid, plague, diarrhea, gastroenteris, dysentery and other diseases.
Stomach and intestine related different diseases are caused by presence of protozoa in drinking water. Main diseases among them are thrombosis, giardiasis, dysentery, amoebic, hepatitis, apses etc.
Parasites enter intestines in the body through drinking water and give birth to various kind of worms including round worms, hip worms, thread worms, tape worms, escarps etc. these cause many diseases.
Apart from the above, wells disease in leptospiral diseases and systosamiasis in snail supported diseases cause adverse effect on human health.
4. Diseases related to water:
When water polluted from various sources is accumulated at a certain place, many mosquitoes, flies and insects are produced which cause malaria, philaria, dengue, yellow fever encephalitis and many other infectious diseases.
5. Diseases caused by chemical substances mixed with water:
Many chemical substances like Fluorides, nitrates and mercury etc. exist in water in liquid form. They can prove harmful if their quantity increases due to human interference. Fluorides affect teeth and bones. Nitrates after joining with hemoglobin, reduce the oxygen carrying capacity of blood, and mercury causes constipation.
A World Health Organization (WHO) report of 1982 had indicated effect of water pollution on man as under:
1. Every year 2,500 persons die in the world due to use of polluted water.
2. Every year 2,500 persons and one crore children die in the world due to non-availability of sufficient water.
3. In the world, 200 crore persons do not get pure and perfect drinking water.
4. In developing countries, four out of every five children die because of water-borne diseases.
5. Every year 50 crore persons suffer from water-borne diseases.
6. 30 per cent population of the world suffers from dysentery.
7. 40 per cent persons suffer from diseases caused by water-borne worms.
Thus man, the main creator of water-borne diseases, suffers most from it and its treatment is also in his hands. There is no other alternative of water on earth. Hence, man can secure his future only by keeping water fresh.
Effects on Animals:
Polluted water affects creatures living in water as well as those using such water. They include fish, tortoises, water birds etc. which live in water and others which move on land, but are affected by use of polluted water. Sea creatures are affected more by thermal, oily, mercury and radioactive pollutants. Fish and other creatures die due to non-availability of sufficient oxygen.
Due to pollution, 40 per cent sea creatures have reduced during the last 50 years. Iraq had burnt oil wells of Kuwait during the Gulf War, due to which biotic life had deteriorated to a large extent. Apart from this, creatures on the earth are also affected by polluted water, which occur when industrial, urban and agricultural effluents mix in drinking water sources.
For example in Lucknow, many fish are dying due to sewage of urban areas mixing in river Gomti. Cows, buffaloes and other animals also die by drinking polluted water. In May 1999, 500 cows had died because of drinking polluted water. Agricultural effluents are also equally harmful. Many poisonous chemicals mix in water and cause diseases. Materials flowing from domestic effluent destroy micro organisms. Thermal pollution kills fish existing in lakes, tanks and seas.
Effects on Plants
Like human beings and other creatures, water pollution affects plants also. Nitrates and phosphate produced by agricultural effluent after mixing with water, result in developing many types of harmful algae which do not allow sunshine to pass. Many useless vegetation grow and harm water plants.
Due to thermal pollution many algae and fungus develop which reduce the quantity of oxygen by causing decay. Vegetation is destroyed by this sewage by polluting water and it support the fast development of algae, fungus and bacteria.
Excreta fungus mainly bacteria, spherotilas, netais, carkesium, polypinum, leptomitus etc. remain spread over water surface. Due to increasing lichens in polluted water, absence of transparency of sunshine is caused and the process of photosynthesis is hindered. This prevents growth of plants.
Thus, water pollution not only affects creatures but also the trees and plants which affect man. Vegetables are being grown by establishing sewerage farms near urban effluents. By consuming them, the food cycle of man is affected.
Effects on Agriculture:
Crops are destroyed by irrigation with polluted water. Soils are also polluted in the process. Harmful elements found in polluted water enter into the soil and reduce its productivity. Apart from this, crops grown with polluted water are not beneficial for the health of human beings.
Water is the basis of the ecological system. Trees and plants as well as other biotic organisms develop according to it. A water deposit is a complete ecological unit and all the living organisms found in it remain in a balance and a food chain is formed. This chain remains healthy till the water remains fresh in the natural form. Food chain becomes imbalanced as soon as water becomes polluted.
Danger is created for the biotic community and many organisms, specially sea creatures become extinct. As Patrick has said, “Water pollution reduces aquatic biodiversity which causes destruction of life in river”. Similarly, due to weeds like water hyacinth and water ferns etc. found in water, vegetation having roots in water and algae are destroyed. Photosynthesis is not possible due to water pollution and it also destroys vegetation in the water.
Grave effect of water pollution is caused on sea creatures. In the absence of availability of proper geographical conditions to planktons, many species of fish are on the brink of extinction. Similarly on the earth, every element of ecological system is being affected by water pollution. Its effect would be worldwide rather than being at the micro level.