1. From Industrial Wastes
When industrial wastes containing poisonous chemicals are dumped carelessly, they contaminate vegetation, surface water as well as ground water supplies. Later on, these chemicals find way into all those organisms that eat the plants or grass pr drink water contaminated with these chemicals. Some of the large variety of industrial pollutants that have been put into our natural waters or buried in the ground on large scale are: acids , bases, salts, metal solutions, oils grease, dyes , waste solvents, poisons such as cyanides and mercury and variety of other chemicals.
Heavy metals such as lead, mercury, manganese, cadmium and chromium are generally toxic to life forms in grater than trace amounts. In many countries, various surface water bodies have already been heavily contaminated with poisonous chemicals posing a serious danger to aquatic life. Fishes living in several highly polluted water bodies such as rivers, lakes and along sea shores where untreated chemical effluents are released are found to be so contaminated with poisonous chemicals that they are considered find way in their bodies and cause many disease. In some cases, fishes are even found dead due to the presence of high concentration of chemicals in water.
2. Accidents in Chemical Factories
Sometimes-chemical pollution caused by the accidental release of some toxic chemical; in the factory. Such accident took place in the Union Carbide Plant at Bhopal in December 1984. In this incidence, highly toxic Methyl Isocyanate (MIC) gas leaked from the plant. This resulted in the death of thousands of people and animals in the surrounding localities. Many more suffered from different types of aliments. The exact impact of the chemical on the health of future generations cannot be assessed.
3. Excessive Use of Fertilizers
The excessive use of chemical fertilizers to boost the production also leads to contamination of various water bodies. Contamination of water with fertilizers leads to very undesirable effects such as eutrophication. This is due to the reason that phosphate and nitrate encourage the growth of algae, which depletes the water body of its oxygen content. As a result, fishes and other aquatic life forms are adversely affected. Moreover, it is well established that nitrate in sufficient concentration is toxic to higher organisms including human beings.
4. Use of Pesticides
The use of pesticides has also increased enormously in the recent past. These pesticides find their way into lakes and rivers and contaminate them. Most of these chemicals are toxic in nature. These chemicals get progressively concentrated in the food chain. These chemicals can cause long-term damage to the health of human beings. These pesticides find also enter our bodies directly if the food articles to which these chemicals are sticking are not thoroughly washed before consuming.
DDT and other chlorinated hydrocarbons, which have long been used as pesticides, have been found to be toxic. DDT is a highly stable compound. It is not easily metabolised (broken down) by animals. It is deposited and stored in the fatty tissues. Since DDT is not easily biodegradable, there is a resultant build up of this toxic chemical within the animals, soil and water over a period. Investigations have revealed that people living in some of the urban areas of our country have alarming amounts of DDT in their bodies. DDT and other non-biodegradable pesticides are now being replaced with biodegradable pesticides.
5. Release of Gaseous Pollutants in Air
Many industries release large number of pollutants in the atmosphere. These pollutants are responsible for variety of diseases. Persons exposed to CO, CO2, SO2, h7ydrocarbons and particulate matter suffer from headache, dizziness, irritation of the eyes and nose, allergies, chest pain and many respiratory disorders.
6. Pollution Caused by Dust
Certain industries give rise to considerable amounts of dust. Workers exposed to various types of injurious dusts suffer from a number of ailments. Following special
Pneumoconiosis is caused by inhalation of coal dust. Workers in coal, mines suffer from this disease.
Silicosis is caused by stone (silica) dust. Workers in stone quarries or those engaged in the cutting and grinding of stone from this disease.
Asbestosis is caused by asbestos dust. Workers involved in the manufacture of Beedis and cigarettes may suffer from this disease.
Siderosis is caused by iron dust.
Workers involved in carpet weaving generally suffer from disorders such as asthma and tuberculosis.. The persons exposed to smoke and other gaseous pollutants are also more prone to lung disorders and infections.
The diseases mentioned above which arise due to occupation in which the individual is involved are called occupational diseases terms are used for the diseases caused by different types of dusts.