The word 'pollution' is derived from the Latin 'pollutionem' which means to make dirty. Environmental pollution has become a serious problem in industrialized societies be¬cause the life- sup¬porting systems of the entire living world have been converted into their own resources and it has disturbed the natural ecological balance. Significant degradation and depletion have happened due to overuse, misuse and mismanagement of resources.
Environmental pollution is defined as an undesirable change in our surround¬ings due to human ac¬tivities that cause changes in the features of land, air or wa¬ter which affect humans / other living beings. Population explosion, rapid industrialization, defores¬tation, unplanned urbanization, scientific and technological advancement, etc. have contributed to environment pollu¬tion.
Air pollution has caused a change in the composition of air is all over the world, especially in industrialized coun¬tries. It results from gaseous emissions released industries, thermal power plants, domestic combustion etc. Most gaseous and particulate air pollutants are produced by burning of fuels. The burning of coal produces mainly carbon dioxide, sulphur dioxide and fly-ash. Lead, carbon monoxide and nitrogen oxides are added to the atmosphere from automobile ex¬haust.
Nitrogen oxides and sulphur dioxide together are responsible for Acid Rain, which means dissolution of these gases in rainwater to produce acidic raindrops. Car¬bon monoxide is highly toxic and affects the oxygen-carrying capacity of human blood. Several deaths are reported every year from carbon monoxide poisoning brought about by gas heaters, heating devices and coal mines.
Lead, emitted by automobiles, hampers haemoglobin forma¬tion. Chloroflurocarbons (CFCs), widely used as propellants and re¬frigerants, cause ozone depletion in the stratosphere. Such depletion has created a big Ozone Hole over the Antarctica, which lets ultra-violet rays from the Sun enter the atmosphere. Excess exposure to ultr-aviolet rays can lead to skin cancer.
Haemoglobin can absorb Nitrous Oxide more easily than oxygen. About 80- 90% NO inhaled is easily absorbed by the blood, which reduces its oxygen- carrying capacity. NO2 weakens the lung tissue and thus causes lung cancer and emphysema (breathing problem) and bronchitis. In sunlight, NO2 reacts with hydrocar¬bons to produce ozone, a highly toxic gas, known to cause asthma.
Water pollution ad¬versely changes the quality of water and upsets the ecosystem and causes health hazards to humans and animals. Water is polluted by the addition of inorganic, organic or biologi¬cal substances.
Effluents from factories, paper mills, sugar mills, tanneries, sew¬age are let into rivers, causing water pollution. Water pollution also occurs due to excess use of pesticides and fer¬tilizers. The enrichment of water by nutrients (esp. nitrate and phosphates) results in eutrophication of lakes and water bodies. This results in excessive growth of algae and loss of dissolved oxygen in the lake. Besides, oil spills from oil tankers, like in the Gulf of Mexico, also cause marine pollution. Various harmful chemicals like DDT can enter our food chain through consumption of polluted water.
Noise is unwanted sound. Whether a given sound is pleasant or not depends on its loudness, duration, rhythm and personal mood. An immediate and acute effect of noise pollution is the impairment of hearing ability, anxiety and stress and, in extreme cases, fear. Such effects are accompanied by increase in heart beat, constriction of blood vessels, digestive spasms and dilation of the pupil. Loudness is measured in decibels (dB).
A barely audible sound would be around 10dB, a whisper is 20dB, and a normal conversation is about 35- 60dB. If you stand at a busy urban traffic light point at peak time for even 5 minutes, you will easily understand the idea of noise pollution. Typically, such busy traffic locations are witness to sound levels beyond 85 dB. Any sound measuring beyond 80dB can be classified as pollution as it can potentially harm the hear¬ing abilities. The WHO has fixed 45dB as the safe noise level for a city.