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This branch of health is concerned with the physical, chemical and biological external factors affecting health. It includes having the knowledge of the effects these hazards pose on man, animals and the environment, and also the necessary remedies. The topic can be studied under two broad divisions: pollution and natural disasters. Natural disasters are the adverse events that results from the displacement of the earth. They include earthquake, tsunami, volcanic eruption, flood and others. Natural disasters degrades the ecosystem, change the environment, lead to loss of lives of man and animals. Many animals lose their habitats, lands lose their quality and pollutants are exposed to the environment when natural disasters occur.
Pollution on the other hand is the introduction of toxic contaminants into the natural environment. The toxic wastes released in pollution are called pollutants. Pollution could affect the air and water; they are also dangerous to human health and aquatic animals. Environmental hazards are classified into physical, chemical, environmental, biological, psychosocial and mechanical. Air pollution is the release of pollutants or harmful substances into the atmosphere. All these gaseous wastes affect the stratosphere, ecosystem, plants and animals. Pollutants are from both natural and artificial processes. Natural sources include volcanic eruption, carbon monoxide, sulphur, dust, radioactive decay, smoke and others. The activities of man that result to pollution are called anthropogenic sources and this include burning of fuels, industrial activities, exhaust wastes from automobiles, wood, fumes from generators and power plants, animal wastes and so on.
Air pollutants could be in solid particle or gaseous forms, natural or artificial. They are divided into primary and secondary pollutants. Primary pollutants are emitted directly through natural process(es) into the atmosphere. Examples are the following ; the ash released through volcanic eruption, sulphur dioxide released in industries through the volcanic eruption and incomplete combustion of fuel and coal ;carbon monoxide released by incomplete combustion of fuel in automobiles, machines and woods; nitrogen dioxide which is emitted from incomplete combustion and electric charges in thunderstorms. Others are the Chlorofluorocarbons which lead to the depletion of the ozone layers, Methane which leads to global warming, Sulphur dioxides lead to acid rain. Toxic metals like lead, ammonia, sewages, industrial wastes, explosives and radioactive substances are all pollutants. Secondary air pollutants are the products of primary pollutants. Examples are ozone which results from fuel and consists of smog. Smog, another example of secondary air pollutants results from sulphur dioxide and coal, the mixture of coal and ultraviolet rays.
Air pollution has a great effect on human health. Air pollutants lead to high rate of respiratory and breathing disorders, asthma, headache, development of allergies, lung cancer, breathing difficulty, coughs, catarrh, stroke, heart infection and death. Paints, ashes, burning of woods are pollutants common in many houses. Mosquito sprays, dusts and pesticides also pose a great harm to human health. Residents inhale these poisonous gases which affects their respiratory organs. Poor ventilation in homes also increases the circulation of the pollutants. Carbon monoxide poisons the blood by mixing with the hemoglobin, thus leading to carboxyhaemoglobin. Industries and factories should be located in outskirts of towns and cities, and not in residential areas. Industrial wastes must be disposed well. Government should coordinate and regulate the activities of the industries. Rooms should be well ventilated, generators and power plants should be situated outside the houses and far from people, products of woods, planks and asbestos must be disposed properly.
Water pollution is the release of pollutants or contaminants into the water bodies, which are the rivers, lakes, streams, dams and oceans. Many industries and farmers dispose their wastes into the water bodies without devising the means of removing or treating them. Both organic and inorganic substances constitute the water pollutants. Organic pollutants are wastes that are derived from living organisms and man’s activities. They include sewages, wastes from food, litters, plastics, garbage, petroleum, oil, chemicals, detergents, agricultural activities, dung, drugs. Inorganic pollutants on the other hand are wastes from heavy chemicals and metals. The contamination of the water bodies may be as a result of natural process. Wastes are also being eroded into the lakes and rivers during rainfall. Pollution of the water bodies has many negative effects such as the increase in the concentration of the composition and increase in the temperature of the water bodies. Introduction of pathogens and contaminants from sewages and wastes from houses and industries often result to these problems and many more such as the change of water colour, odor, irritating smell from water bodies. Water pollution affects the aquatic plants and animals.
The presence of wastes in the water can reduce the concentration of oxygen used by aquatic animals. This can lead to the death of aquatic lives. Heavy contaminants lead to cloudiness and reduce the passage of light rays in the water. Turbidity hinders the process of photosynthesis of aquatic plants. The pH level of water can reduce, thereby making the water acidic and dangerous for plants, animals and man. Beach blockage is another adverse effect associated with water pollution. Water bodies flow above their banks when their passages have been blocked by refuse and waste. This leads to flooding of houses and streets which can result to loss of lives and properties. The discharge of wastes and sewages lead to the presence of micro-organisms which makes the water unsafe for use and drinking. Water is essential to life, we need water for drinking, cooking, washing and farming. Aquatic animals also need it for survival, as it is their habitat. There is need to regulate how wastes are being disposed by the industries, farms and houses. The act of dumping refuse into the lakes, streams and rivers should be banned. Drainages should be constructed for sewage disposal. Wastes should be recycled; the water bodies should be treated and recycled for use.
Land pollution or land degradation refers to the usage of land that result to decrease in the quality, productivity of land and soil. Deforestation, erosion, industrial activities, mining, use of fertilizers by farmers, construction processes are some of the factors that have led to the reduction of land’s value and soil quality. The removal or felling of trees without replacement deteriorates land’s value. Erosion is the washing off of the topmost layer of soil. Nutrients necessary for plants growth are being washed off by erosion. Mulching which is the process of covering exposed land with plants or vegetables should be practiced during bush fallowing. Deforestation and long period of fallow expose the soil to erosion, affect the balance of the ecosystem which in turn leads to air pollution such as green house effect and global warming. Afforestation, that is, tree replacement should be done when matured trees are cultivated. The lands must not be bare and exposed to erosion.
Farmers’ application of fertilizers to crops reduces soil quality. The process of drilling deep into the earth surface during mining degrades the soil and can sometimes lead to earth movement or quakes. Household wastes are being dumped on lands. Many lands are being converted by industries and households to landfill sites. All these can affect the respiratory system due to foul smell of refuse dumps. They also lead to the loss of soil fertility, degradation of the ecosystem, communicable diseases, increase in pests and rodents. Animals are being displaced with wrong land use, they lose their habitats, environment and many die in the process.
Noise pollution is the excessive noise dangerous to man and animals. Aircrafts, machines used by industries, automobiles and other means of transportation, noise from musical instruments, radios, televisions and stereos are sources of noise pollution. Residential buildings close to industries, airports, railways are more exposed to noise disturbances. It results to hypertension, stroke, anxiety, hearing problems, cardiovascular issues, and psychological disturbances in man. Noise interferes with sleep, man’s activities, assimilation, concentration, and lots more. Noise can change the delicate balance in predator-prey detection and avoidance. Sound absorbers should be used in airports, railways, airports and industries should not be located in residential areas, all these would reduce noise pollution and increase overall health.
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