Water Pollution
It involves addition of substances or energy forms into water bodies in quantities thata re harmful to the living organism dependant on that water.
Sources of water pollution
a) Domestic effluents Untreated sewage from urban centres gets discharged into rivers used for water supplies for domestic purposes. This sewage contains disease causing micro-organisms such as bacteria, viruses and protozoa. It is also full of faecal material and urine which encourage bacterial growth. Kitchen waste also contains detergents that have a lot of phosphates.
Effects Water pollution may also cause epidemics of waterborne diseases e.g cholera, typhoid and amoebic dysentery. The faecal material is broken down by saprophytic bacteria and fungi which lead to depletion of dissolved oxygen in water. This in turn affects the aquatic animals such as fish and aquatic plants. The breakdown of theses organic matter releases such as nitrates, phosphates and sulphates which enrich the water body resulting in eutrophication as happened with excessive growth of water hyacinth in lakes.
b) Industrial Effluents Industries discharge various effluents into rivers, fresh waters, dams, marshes, seas and oceans. The effluents contain toxic metallic compounds of mercury, arsenic and cadmium in addition to acids and there chemicals. Effects The poisonous compounds directly kill aquatic organisms such as fish. Death can also be caused indirectly through eutrophication. These compounds also enter the food chain or accumulate to lethal levels in organisms higher up the trophic level.
c) Heat Industries discharge hot water directly into water bodies. This may be from the cooling process or for discharging industrial effluents. Some of the effluents may react among themselves releasing heat into the water. Effects Heat reduces the amount of dissolved gases in water e.g oxygen and carbon (IV) oxide. Thus organisms may die from oxygen deficiency or lack of photosynthesis. Heat releases respiratory rate to abnormal levels causing malfunctioning in the organisms. The hot water may then kill the living organisms directly due to high temperatures.
d) Oil spillage Oil is an important pollutant. Oil spillages occur in oceans from oil tanker accidents, offshore oil wells and refineries and also from damaged warships. Effects Oil layer on water reduces oxygen supply to the water and this may lead to death of aquatic life forms. Marine organisms such as fish are killed by clogging of their respiratory surfaces. Marine birds gets their feathers clogged hence the difficult in flight. Oils coats photosynthetic phytoplantktons till they die. There is reduced light penetration into the water hence photosynthesis of a submerged plant is hindered.
e) Agro-chemicals Agricultural chemicals include inorganic fertilizers, herbicides and pesticides. The inorganic fertilizers contain phosphates and nitrates. Pesticides may contain heavy metals such as mercury and copper. Other pesticides such as DDT contain chloroflourocarbons which are not easily broken down biologically. These chemicals and fertilizers percolate through soil and after underground seepage they join streams and rivers and eventually into lakes and oceans. Effects Since most of chemicals contain the heavy metals such as copper and mercury, they affect the respiratory activities of aquatic organisms. These chemicals find their way into the organism bodies in small amounts. However they accumulate over a long time and reach toxic levels leading to death. Furthermore they accumulate along food chain becoming lethal at higher trophic levels. Nitrates and phosphates in fertilizers cause eutrophication.
f) Lead This is water pollutant mainly from pipes and tanks in domestic water supply systems. Through run-off it finds its way into water bodies like rivers, lakes and oceans. The effects of lead whether inhale or ingested are similar as discussed under air pollution
g) Mercury Mercury as a pollutant is released by industries that manufacture chlorine, sodium hydroxide, ores and vinyl plastics. It is also released during combustion of coal and petroleum oils. Fungicides and some cosmetics also contain mercury. The mud in some rivers contains mercury which is converted to methyl mercury by methane producing bacteria. Effects Methyl mercury is volatile and very toxic. It is absorbed by aquatic organisms or through leaves and roots of plants hence entering the food web involving human beings. Mercury poisoning in people results in accumulation of mercury in liver, kidneys and brain affecting the physiological functioning and eventually causes death. Animals eating plants with mercury are poisoned and killed as observed in wood-pigeons. Mercury also interferes with the process of melanin formation leading to skin lightening, blindness paralysis and even death.
h) Soil Erosion Through soil erosion, silt is transported into water bodies. Effects This makes water unclean and unfit for human consumption. The silt particularly reduces light penetration hence hindering photosynthesis activity. It also clogs the respiratory surfaces of aquatic organisms. E.g gills in fish and stomata in plants. This interferes with gaseous exchange.
Control of Water Pollution
a) Legislation
b) Industries should control or treat the industrial effluents before discharge into the water bodies.
c) Proper treatment and disposal of sewage. Here should be separate systems for disposal of sewage and drinking water. Latrine should be connected properly used in addition to proper personal hygiene to control disease causing agents.
d) Encourage the use of unleaded petrol.
e) The public should be educated on correct amount of inorganic fertilisers and pesticides to be used.
f) Appropriate soil erosion control methods to be put in place such as building of gabions, terraces, mulching and growing of soil cover crops.
Soil Pollution Sources of soil pollution Either intentionally or accidentally human beings discharge chemicals into the soil which accumulate to levels that cause harm to soil organisms.
a) Oxides of sulphur e.g sulphur (IV) oxide enter the soil through precipitation as acid rain. Acid rain alters the pH therefore affecting plants and animals that cannot tolerate acid soil. However, acid rain may promote the growth of plants that tolerate acidic conditions. Acid rain also causes leaching of minerals leading to loss of soil fertility.
b) Aerosols Most aerosols sprayed to control pest and diseases in plants and animals contain heavy metals e.g copper and mercury. The chemicals fall on the soil and are taken up by plants where their concentration increases. As animals eat these plants, toxicity increases and leads to death of animals. These chemicals kill nitrogen fixing soil micro-organisms hence lowering the soil fertility with consequent reduction of plant growth. c) Petroleum Products Petroleum products spilled on land e.g oil tankers. Soils organisms fail to obtain oxygen in oil saturated soils therefore die. Coating of plant leaves or respiratory surfaces of animals also leads to their death. d) Inorganic fertilizers Agricultural inorganic fertlilisers contain phosphates and nitrates. Theses increase soil acidity so that soil micro organism cannot inhabit such soils. Formation of soil organic matter slows down and then stops. Soils become exhausted hence plant and animal life ceases. In addition soil structure ids changed hence encouraging soil erosion. e) Solid Waste Community, household wastes and industrial wastes. Some are biodegradable e.g food residues, old clothing and papers. Others are non-biodegradable e.g rubber, plastic containers, scrap metals and glass bottles. Soil waste is a nuisance and also may ne injurious e.g glass bottles. They destroy the aesthetic state of the environment. They offer breeding grounds for pests, rodents and insect vectors which in turn pose health hazards to human beings. The non-biodegradable solid wastes limit soil aeration thus inhibiting micro-organisms activity. Control of Soil Pollution All solid wastes should be sorted out according to manufacture instructions and specifications , then appropriate disposal methods applied. a) Recycle solid wastes e.g polythene paper and plastic containers, glass bottles, paer and scrap metal b) Household wastes that are biodegradable can be disposed in a compost pit to form compost manure for organic farming. c) Combustible solid wastes .g old clothes, sanitary towels, hair should be burned in incinerators. d) Discourage excessive use of agro-chemicals. e) Biological control of pests and disease to be encouraged. f) Encourage pipeline transportation of petrol and petroleum products to minise risk of spillage. g) Enforce appropriate legislation on proper solid waste management. Radioactive Emissions Nuclear emissions can also be the cause of soil, air and water pollution. Although nuclear energy is available in limitless quantity, its harnessing, management and risks of damage of life are very high. It is based on the destruction of the atom of matter to release energy that holds the constituents of the atom. The form in which this energy is released when atoms are broken down into generally called radiators. Such radiation has very great power and is very destructive if it leaks accidently. The industries in which this energy is produced are called radioactive or nuclear reactors. Some of the common substances broken down to release nuclear energy are uranium, radium, germanium, plutonium and hydrosonium (heavy water). Use of Nuclear Energy Nuclear energy is used in generation of electricity and propelling of nuclear war planes, nuclear propelled ocean vessels, spaceships and submarines. Effects of Radioactive Emissions a) Increased mutation rates with increased abnormalities some of which are inheritable. b) It causes cancer such as borne tumuors and leukaemia. c) Excess doses of radioactive emissions cause so much damage leading to death Control Due to potential dangers of nuclear waste disposal and energy management, the control is only by dialogue between nations with the nuclear technology. HUMAN DISEASES A disease is disorder state of tissue, organ, system or organism, during which its function are not carried on normally. In human beings, disease results from genetic disorders, nutritional deficiencies or infections by other organisms and viruses. Bacterial Diseases a) Cholera This is diseases by a bacterium known as Vibrio cholerae found in infected water and are passed o by flies to food thereby contaminating the food. People living in unhygienic places i.e where sanitation is poor and the domestic water supply is contaminated, can easily contract the disease. Once there is an outbreak of the disease, it spreads rapidly and can cause an epidemic. Symptoms The incubation periods varies between one to six days depending on the magnitude of the infection and the taste of the health of the individual. The bacteria reach the intestines and multiply rapidly. They secret an enzyme called Mucinase which digests the inner lining of the intestines. The exposed intestinal wall then becomes irritated and damaged by the causes violet diarrhoea and vomiting. This is accompanied by severe abdominal pains. The disease develops rapidly and leads to general body dehydration owing to the high frequency of defecation, accompanied by loss of large quantities of water. Death by cholera can be rapid within 24 hours of infection. Prevention and Treatment Sanitary disposal of faeces and refuse is needed to prevent the contamination of water and food. The pit latrine in rural areas should be deep. They should be kept clean to keep away flies. Personal hygiene should be maintained. Domestic water should be boiled and filtered, or chlorinated before use so as to kill bacteria and their spores. The infected persons are infectious and so should be isolated and treated as soon as possible. Treatment involves administering of antibiotics drugs in order o kill the bacteria. Oral rehydration salts should be administered before treatment. b) Typhoid This is also a disease caused by a bacterium called salmonella typhi. The bacteria are passed out either through urine or faeces. Poor disposal of urine and faeces may cause contamination of the water supply from rivers, dams and lakes. Healthy individuals can be infected by taking contaminated water or food. Symptoms Its incubation period last for about two weeks after which a fever and rush develop, followed by severe diarrhea. The bacteria attack the walls of the intestines and cause patches of scores. Patients are advised not to eat solid food as it might irritate the intestinal sores and cause bleeding. In severe attacks the sores may burst and cause perforation in the intestines. This may result in death if the patient is not treated early enough. The bacteria invade the lymph glands around the intestines and then pass into the blood stream. Patients do not develop immunity of this disease and therefore one can be attacked again and again. Prevention and Treatment There should be proper disposal of faeces and urine to prevent spread of the bacteria. Domestic water should be boiled or chlorinated before drinking to kill the bacteria. Hands and cutlery should be washed with clean water before being eaten. Food handlers should be clean, and should be subjected to regular medical check-ups. Healthy people may be vaccinated with attenuated (weakened) typhoid bacteria in order to provide immunity for at least two years. Treatment involves administering antibiotics. Protozoan Diseases a) Amoebic Dysentry Amoebic dysentery is a disease caused by protozoan called entomoelaba histolytica. When the amoeba cysts are ingested, the cysts membrane is digested and the protozoa is released. When they reach the large intestines and colon, the E. histolytica multiply. Symptoms Normally E. histolytcia live within the lumen of the colon and feed on bacteria without harming the host. At certain times, they invade the mucosal wall of the colon and produce a tissue-dissolving enzyme called histolysin. This result in formation of ulcers on the colon wall and the parasites then fed on the red blood cells at the site of the ulcers. This condition usually leads to diarrhea or amoebic dysentery and faeces contain blood. The disease is usually characterized by diarhhoea, dehydration, fever and abdominal pains and severe pain when passing stool. The infection may also become systemic(i.e invade the blood stream), and parasites may reach other tissues or organs of the body such as liver, lungs and brain where they produce abscesses which may be fatal. Prevention and Treatment Prevention of the infection aims at avoiding contamination of food or water with cysts. Control measures include boiling water for drinking, proper food storage and proper faecal disposal. For treatment a number of amoebicides can be used. b) Malaria Malaria is a disease caused by protozoan parasitic called plasmodium. They are four different species of plasmodium namely P. vivax, P. ovale,P. falciparium & P. malariae. The plasmodium is transmitted from an infected person to a healthy person by female anopheles mosquito. When the mosquito bites an infected person it sucks blood containing the parasites. Inside the mosquito, the plasmodia develop into infective stages. When the same mosquito next bites a healthy person it passes on the infective plasmodia from its salivary glands into the blood into the blood system of the healthy person. The incubation period lasts between seven to ten days. During this period that parasites invade the liver cells where they multiply. They are then released into the bloodstream where they now attack and destroy the red blood cells. Symptoms The symptoms of malaria include high regular fevers accompanied by profuse sweating punctuated by chills and shivers, headaches, muscle and joint pains are felt most of the time. The patient lacks appetide and vomits from time to time. There is enlargement of liver and spleen. Anaemia results because of the destruction of red blood cells. In severe attacks, it leads to convulsions in children. Malaria is a killer disease. Prevention and treatment Various methods of prevention are available in the management of malaria. The most recent method is the development of vaccines against the plasmodium. These targets various stages in the life cycle of the parasite hence developing some immunity. Traditionally malaraia has been controlled by use of nets to repellents such as creams and mosquito coils have been used. Insecticides are sprayed in dwelling places and also use of treated mosquito nets. Drainage of stagnant water and clearance of vegetation around houses destroys the breeding and resting sites of mosquitoes hence reduction in their numbers. Tins, plastic containers and polythene papers that hold water should also be destroyed. The use of oil on stagnant water has been useful but it is being replaced by powdery treatment of water of water services. Biological control involves use of fish in pounds to feed on the mosquito larvae. A more recent method involves release of genetically sterilized male mosquitoes to mate hence reducing the number of mosquitoes. People travelling in malaria prone areas are advised to take antimalarial drugs for prevention. Treatment should be preceded by proper diagnosis and the full dosage administered for full care. Under dose often leads to development of resistance. The international Stockholm Convention of which Kenya is signatory restricts the use of DDT to public health where no alternatives are available. However Kenya the leading producer of pyrethrum strongly advocates for the use of natural pyrethroids in mosquito control. These have been proved effective and safer to environment because they are bio-degradable. Although a lot of resources have been channeled into malarial control, it has been difficult to eradicate disease. Several factors continue to frustrate theses efforts. Theses include; • The presence of large reservoir of the parasite in other hosts such as monkeys and birds. • The warm tropical conditions provide extremely suitable breeding conditions hence rapid multiplication of the vectors. • The development to resistance to insecticides used against mosquitoes. Similarly the plasmodium parasite quickly develops resistance against the drug used against it. • The individual countries face financial constraints. Furthermore regional conflicts frustrate co-ordinated program. Government and donor funds are often diverted to purchase weapons and other military ware. Parasitic Worms Askaris Lumbricoides Ascaris lumbricoides is a parasitic roundworm which belongs to the phylum Nemoda. Ascaris Lumbricoides is widespread in distribution and infects small intestines of pigs and human beings. It may also occur in other organs of the body. The genus Ascaris is the largest nematode parasitic to humans. It is characterized by brownish yellow colour with mouth parts having three lips. The male is about 25 cm long and 0.4 cm in diameter, while te female is about 35 cm long and 0.5 cm in diameter. Mode of Transmission The adult female lays eggs in the small intestine of the host. The eggs are passed out with the faeces and may be swallowed by a new host through contaminated water and food. Contaminated vegetables or fruits which are not washed well before being eaten are also the source of infection. There is also direct infection from faeces to mouth by hand s especially in children. When they are swallowed by a host, the eggs shells are dissolved, releasing the larvae. This penetrates the intestinal walls and enters the bloodstream. They move to liver and then to the heart and lungs. In the alveoli they grow and moult twice. The larvae then migrates up to the trachea where they cause irritation and so are coughed out and so may be swallowed down in to the aeosophogus, stomach and small intestines where they finally mature in adults. Effects of the parasite on the Host During the migration of the larvae they cause irritation in the trachea that lead to lung damage and infection with other diseases. If the is heavy, a lot of is digested food is consumed by the parasite in intestine and this leads o malnutrition in host, especially n children. During their cycle in human host, the parasite feed on blood and therefore can cause anaemia on host. Very heavy infection can also lead to intestinal blockage where victims develop large round stomachs. The worms may also enter the bile duct, pancreatic duct and appendix, causing further complications. Adaptative characteristics of Ascaris lumbricoides to its parasitic mode of life 1. Ascaris lumbricoides has two hosts, human beings and pigs. This ensures that it always has a ready host for survival. 2. It lays many eggs to increase the chance of survival even when some are destroyed. 3. The eggs have protective shell to survive harsh environmental conditions. 4. Ascaris lumbricoides have a thick elastic cuticle which protects it against the digestive enzymes of the host enabling it to survive in the alimentary canal. 5. It has tissues tolerant to low oxygen concentration characteristic of the gut. 6. It has a muscular pharynx through which it sucks digested food from host intestine into its own gut. Prevention and treatment Proper sanitary disposal methods are required especially the availability and proper use of toilet facilities. High standards of personal hygiene should be observed such as washing hands after a visit to the toilet. Hygienic handling and cleaning of fruits and vegetables is necessary. Drinking water should be boiled. Treatment involves use of drugs to kill the worms or inactivate the eggs. Schistomomiasis (Bilharzia) This is a parasite disease of the blood. It is caused by a flatworm of the phylum platyhelminthes of the genus Schistosoma. There are three different species odf the schistosoma that infet human beings. These include Schitosoma mansoni, Schistoma haematobium and Schistosoma japonicum. The parasite is found in fresh water canals, lakes, dams, rice-growing fields and other similar habitats. Modes of transmission The parasite is spread when people drinking water contaminated by larval form called cercariae. Also the parasite can penetrate the skin when bathing or wading through water conatini the larvae. Once in the body they get into the bloodstreams and migrate to the liver where they mature into adults. After coupling of the adult worms, eggs are shed into the blood vessels or alimentary tract. When the faeces or urine containing eggs are disposed of into water, the eggs hatch into larvae called miracidia. The miracidia find and penetrate the water snails such as Biomphalaria and Bulinus. It is from the snails that infective stages cercariae emerge and can now infect human beings who stand, bath or drink in such water. Effects of Parasite on its Hosts The parasite damages the host skin when penetrating and this causes itching. Once in the blood the adult schistosoma releases chemical substances that cause fever. The adult worms have spines which they use to tear through the veins and enter into the intestines or urinary bladder. This causes blood to appear in urine or stool. This can eventually lead to anaemia. The person also experiences abdominal pains and diarrhea. If untreated, the disease can result in death due to exhaustion or by infection from other diseases due to reduced body immunity. Adaptative Characteristic of Schistosoma The parasite has suckers for attachment so that they are not dislodged. The parasite has two hosts, that is the secondary host, the snail and the primary host, the human being. This increases its chances of transfer to several hosts and from one place to another. The cercariae larvae and eggs of the parasite have glands that secrete lytic enzymes which soften tissue to allow for penetration into the hosts. Some larval forms e.g miracidia, are encysted and can remain dormant and viable until they come into contact with a human being. The parasite reproduces through larval forms e.g cercariae, and redia in snails. This makes it very difficult to eradicate the parasite and also increases its chances of transmission and survival. The adult worm in blood produces chemical substances which protect it against the hosts defence mechanism. The worms are of separate sexes. The male form a gynecophoric canal in which it carries the female. This ensures that the e
Sources of water pollution
a) Domestic effluents Untreated sewage from urban centres gets discharged into rivers used for water supplies for domestic purposes. This sewage contains disease causing micro-organisms such as bacteria, viruses and protozoa. It is also full of faecal material and urine which encourage bacterial growth. Kitchen waste also contains detergents that have a lot of phosphates.
Effects Water pollution may also cause epidemics of waterborne diseases e.g cholera, typhoid and amoebic dysentery. The faecal material is broken down by saprophytic bacteria and fungi which lead to depletion of dissolved oxygen in water. This in turn affects the aquatic animals such as fish and aquatic plants. The breakdown of theses organic matter releases such as nitrates, phosphates and sulphates which enrich the water body resulting in eutrophication as happened with excessive growth of water hyacinth in lakes.
b) Industrial Effluents Industries discharge various effluents into rivers, fresh waters, dams, marshes, seas and oceans. The effluents contain toxic metallic compounds of mercury, arsenic and cadmium in addition to acids and there chemicals. Effects The poisonous compounds directly kill aquatic organisms such as fish. Death can also be caused indirectly through eutrophication. These compounds also enter the food chain or accumulate to lethal levels in organisms higher up the trophic level.
c) Heat Industries discharge hot water directly into water bodies. This may be from the cooling process or for discharging industrial effluents. Some of the effluents may react among themselves releasing heat into the water. Effects Heat reduces the amount of dissolved gases in water e.g oxygen and carbon (IV) oxide. Thus organisms may die from oxygen deficiency or lack of photosynthesis. Heat releases respiratory rate to abnormal levels causing malfunctioning in the organisms. The hot water may then kill the living organisms directly due to high temperatures.
d) Oil spillage Oil is an important pollutant. Oil spillages occur in oceans from oil tanker accidents, offshore oil wells and refineries and also from damaged warships. Effects Oil layer on water reduces oxygen supply to the water and this may lead to death of aquatic life forms. Marine organisms such as fish are killed by clogging of their respiratory surfaces. Marine birds gets their feathers clogged hence the difficult in flight. Oils coats photosynthetic phytoplantktons till they die. There is reduced light penetration into the water hence photosynthesis of a submerged plant is hindered.
e) Agro-chemicals Agricultural chemicals include inorganic fertilizers, herbicides and pesticides. The inorganic fertilizers contain phosphates and nitrates. Pesticides may contain heavy metals such as mercury and copper. Other pesticides such as DDT contain chloroflourocarbons which are not easily broken down biologically. These chemicals and fertilizers percolate through soil and after underground seepage they join streams and rivers and eventually into lakes and oceans. Effects Since most of chemicals contain the heavy metals such as copper and mercury, they affect the respiratory activities of aquatic organisms. These chemicals find their way into the organism bodies in small amounts. However they accumulate over a long time and reach toxic levels leading to death. Furthermore they accumulate along food chain becoming lethal at higher trophic levels. Nitrates and phosphates in fertilizers cause eutrophication.
f) Lead This is water pollutant mainly from pipes and tanks in domestic water supply systems. Through run-off it finds its way into water bodies like rivers, lakes and oceans. The effects of lead whether inhale or ingested are similar as discussed under air pollution
g) Mercury Mercury as a pollutant is released by industries that manufacture chlorine, sodium hydroxide, ores and vinyl plastics. It is also released during combustion of coal and petroleum oils. Fungicides and some cosmetics also contain mercury. The mud in some rivers contains mercury which is converted to methyl mercury by methane producing bacteria. Effects Methyl mercury is volatile and very toxic. It is absorbed by aquatic organisms or through leaves and roots of plants hence entering the food web involving human beings. Mercury poisoning in people results in accumulation of mercury in liver, kidneys and brain affecting the physiological functioning and eventually causes death. Animals eating plants with mercury are poisoned and killed as observed in wood-pigeons. Mercury also interferes with the process of melanin formation leading to skin lightening, blindness paralysis and even death.
h) Soil Erosion Through soil erosion, silt is transported into water bodies. Effects This makes water unclean and unfit for human consumption. The silt particularly reduces light penetration hence hindering photosynthesis activity. It also clogs the respiratory surfaces of aquatic organisms. E.g gills in fish and stomata in plants. This interferes with gaseous exchange.
Control of Water Pollution
a) Legislation
b) Industries should control or treat the industrial effluents before discharge into the water bodies.
c) Proper treatment and disposal of sewage. Here should be separate systems for disposal of sewage and drinking water. Latrine should be connected properly used in addition to proper personal hygiene to control disease causing agents.
d) Encourage the use of unleaded petrol.
e) The public should be educated on correct amount of inorganic fertilisers and pesticides to be used.
f) Appropriate soil erosion control methods to be put in place such as building of gabions, terraces, mulching and growing of soil cover crops.
Soil Pollution Sources of soil pollution Either intentionally or accidentally human beings discharge chemicals into the soil which accumulate to levels that cause harm to soil organisms.
a) Oxides of sulphur e.g sulphur (IV) oxide enter the soil through precipitation as acid rain. Acid rain alters the pH therefore affecting plants and animals that cannot tolerate acid soil. However, acid rain may promote the growth of plants that tolerate acidic conditions. Acid rain also causes leaching of minerals leading to loss of soil fertility.
b) Aerosols Most aerosols sprayed to control pest and diseases in plants and animals contain heavy metals e.g copper and mercury. The chemicals fall on the soil and are taken up by plants where their concentration increases. As animals eat these plants, toxicity increases and leads to death of animals. These chemicals kill nitrogen fixing soil micro-organisms hence lowering the soil fertility with consequent reduction of plant growth. c) Petroleum Products Petroleum products spilled on land e.g oil tankers. Soils organisms fail to obtain oxygen in oil saturated soils therefore die. Coating of plant leaves or respiratory surfaces of animals also leads to their death. d) Inorganic fertilizers Agricultural inorganic fertlilisers contain phosphates and nitrates. Theses increase soil acidity so that soil micro organism cannot inhabit such soils. Formation of soil organic matter slows down and then stops. Soils become exhausted hence plant and animal life ceases. In addition soil structure ids changed hence encouraging soil erosion. e) Solid Waste Community, household wastes and industrial wastes. Some are biodegradable e.g food residues, old clothing and papers. Others are non-biodegradable e.g rubber, plastic containers, scrap metals and glass bottles. Soil waste is a nuisance and also may ne injurious e.g glass bottles. They destroy the aesthetic state of the environment. They offer breeding grounds for pests, rodents and insect vectors which in turn pose health hazards to human beings. The non-biodegradable solid wastes limit soil aeration thus inhibiting micro-organisms activity. Control of Soil Pollution All solid wastes should be sorted out according to manufacture instructions and specifications , then appropriate disposal methods applied. a) Recycle solid wastes e.g polythene paper and plastic containers, glass bottles, paer and scrap metal b) Household wastes that are biodegradable can be disposed in a compost pit to form compost manure for organic farming. c) Combustible solid wastes .g old clothes, sanitary towels, hair should be burned in incinerators. d) Discourage excessive use of agro-chemicals. e) Biological control of pests and disease to be encouraged. f) Encourage pipeline transportation of petrol and petroleum products to minise risk of spillage. g) Enforce appropriate legislation on proper solid waste management. Radioactive Emissions Nuclear emissions can also be the cause of soil, air and water pollution. Although nuclear energy is available in limitless quantity, its harnessing, management and risks of damage of life are very high. It is based on the destruction of the atom of matter to release energy that holds the constituents of the atom. The form in which this energy is released when atoms are broken down into generally called radiators. Such radiation has very great power and is very destructive if it leaks accidently. The industries in which this energy is produced are called radioactive or nuclear reactors. Some of the common substances broken down to release nuclear energy are uranium, radium, germanium, plutonium and hydrosonium (heavy water). Use of Nuclear Energy Nuclear energy is used in generation of electricity and propelling of nuclear war planes, nuclear propelled ocean vessels, spaceships and submarines. Effects of Radioactive Emissions a) Increased mutation rates with increased abnormalities some of which are inheritable. b) It causes cancer such as borne tumuors and leukaemia. c) Excess doses of radioactive emissions cause so much damage leading to death Control Due to potential dangers of nuclear waste disposal and energy management, the control is only by dialogue between nations with the nuclear technology. HUMAN DISEASES A disease is disorder state of tissue, organ, system or organism, during which its function are not carried on normally. In human beings, disease results from genetic disorders, nutritional deficiencies or infections by other organisms and viruses. Bacterial Diseases a) Cholera This is diseases by a bacterium known as Vibrio cholerae found in infected water and are passed o by flies to food thereby contaminating the food. People living in unhygienic places i.e where sanitation is poor and the domestic water supply is contaminated, can easily contract the disease. Once there is an outbreak of the disease, it spreads rapidly and can cause an epidemic. Symptoms The incubation periods varies between one to six days depending on the magnitude of the infection and the taste of the health of the individual. The bacteria reach the intestines and multiply rapidly. They secret an enzyme called Mucinase which digests the inner lining of the intestines. The exposed intestinal wall then becomes irritated and damaged by the causes violet diarrhoea and vomiting. This is accompanied by severe abdominal pains. The disease develops rapidly and leads to general body dehydration owing to the high frequency of defecation, accompanied by loss of large quantities of water. Death by cholera can be rapid within 24 hours of infection. Prevention and Treatment Sanitary disposal of faeces and refuse is needed to prevent the contamination of water and food. The pit latrine in rural areas should be deep. They should be kept clean to keep away flies. Personal hygiene should be maintained. Domestic water should be boiled and filtered, or chlorinated before use so as to kill bacteria and their spores. The infected persons are infectious and so should be isolated and treated as soon as possible. Treatment involves administering of antibiotics drugs in order o kill the bacteria. Oral rehydration salts should be administered before treatment. b) Typhoid This is also a disease caused by a bacterium called salmonella typhi. The bacteria are passed out either through urine or faeces. Poor disposal of urine and faeces may cause contamination of the water supply from rivers, dams and lakes. Healthy individuals can be infected by taking contaminated water or food. Symptoms Its incubation period last for about two weeks after which a fever and rush develop, followed by severe diarrhea. The bacteria attack the walls of the intestines and cause patches of scores. Patients are advised not to eat solid food as it might irritate the intestinal sores and cause bleeding. In severe attacks the sores may burst and cause perforation in the intestines. This may result in death if the patient is not treated early enough. The bacteria invade the lymph glands around the intestines and then pass into the blood stream. Patients do not develop immunity of this disease and therefore one can be attacked again and again. Prevention and Treatment There should be proper disposal of faeces and urine to prevent spread of the bacteria. Domestic water should be boiled or chlorinated before drinking to kill the bacteria. Hands and cutlery should be washed with clean water before being eaten. Food handlers should be clean, and should be subjected to regular medical check-ups. Healthy people may be vaccinated with attenuated (weakened) typhoid bacteria in order to provide immunity for at least two years. Treatment involves administering antibiotics. Protozoan Diseases a) Amoebic Dysentry Amoebic dysentery is a disease caused by protozoan called entomoelaba histolytica. When the amoeba cysts are ingested, the cysts membrane is digested and the protozoa is released. When they reach the large intestines and colon, the E. histolytica multiply. Symptoms Normally E. histolytcia live within the lumen of the colon and feed on bacteria without harming the host. At certain times, they invade the mucosal wall of the colon and produce a tissue-dissolving enzyme called histolysin. This result in formation of ulcers on the colon wall and the parasites then fed on the red blood cells at the site of the ulcers. This condition usually leads to diarrhea or amoebic dysentery and faeces contain blood. The disease is usually characterized by diarhhoea, dehydration, fever and abdominal pains and severe pain when passing stool. The infection may also become systemic(i.e invade the blood stream), and parasites may reach other tissues or organs of the body such as liver, lungs and brain where they produce abscesses which may be fatal. Prevention and Treatment Prevention of the infection aims at avoiding contamination of food or water with cysts. Control measures include boiling water for drinking, proper food storage and proper faecal disposal. For treatment a number of amoebicides can be used. b) Malaria Malaria is a disease caused by protozoan parasitic called plasmodium. They are four different species of plasmodium namely P. vivax, P. ovale,P. falciparium & P. malariae. The plasmodium is transmitted from an infected person to a healthy person by female anopheles mosquito. When the mosquito bites an infected person it sucks blood containing the parasites. Inside the mosquito, the plasmodia develop into infective stages. When the same mosquito next bites a healthy person it passes on the infective plasmodia from its salivary glands into the blood into the blood system of the healthy person. The incubation period lasts between seven to ten days. During this period that parasites invade the liver cells where they multiply. They are then released into the bloodstream where they now attack and destroy the red blood cells. Symptoms The symptoms of malaria include high regular fevers accompanied by profuse sweating punctuated by chills and shivers, headaches, muscle and joint pains are felt most of the time. The patient lacks appetide and vomits from time to time. There is enlargement of liver and spleen. Anaemia results because of the destruction of red blood cells. In severe attacks, it leads to convulsions in children. Malaria is a killer disease. Prevention and treatment Various methods of prevention are available in the management of malaria. The most recent method is the development of vaccines against the plasmodium. These targets various stages in the life cycle of the parasite hence developing some immunity. Traditionally malaraia has been controlled by use of nets to repellents such as creams and mosquito coils have been used. Insecticides are sprayed in dwelling places and also use of treated mosquito nets. Drainage of stagnant water and clearance of vegetation around houses destroys the breeding and resting sites of mosquitoes hence reduction in their numbers. Tins, plastic containers and polythene papers that hold water should also be destroyed. The use of oil on stagnant water has been useful but it is being replaced by powdery treatment of water of water services. Biological control involves use of fish in pounds to feed on the mosquito larvae. A more recent method involves release of genetically sterilized male mosquitoes to mate hence reducing the number of mosquitoes. People travelling in malaria prone areas are advised to take antimalarial drugs for prevention. Treatment should be preceded by proper diagnosis and the full dosage administered for full care. Under dose often leads to development of resistance. The international Stockholm Convention of which Kenya is signatory restricts the use of DDT to public health where no alternatives are available. However Kenya the leading producer of pyrethrum strongly advocates for the use of natural pyrethroids in mosquito control. These have been proved effective and safer to environment because they are bio-degradable. Although a lot of resources have been channeled into malarial control, it has been difficult to eradicate disease. Several factors continue to frustrate theses efforts. Theses include; • The presence of large reservoir of the parasite in other hosts such as monkeys and birds. • The warm tropical conditions provide extremely suitable breeding conditions hence rapid multiplication of the vectors. • The development to resistance to insecticides used against mosquitoes. Similarly the plasmodium parasite quickly develops resistance against the drug used against it. • The individual countries face financial constraints. Furthermore regional conflicts frustrate co-ordinated program. Government and donor funds are often diverted to purchase weapons and other military ware. Parasitic Worms Askaris Lumbricoides Ascaris lumbricoides is a parasitic roundworm which belongs to the phylum Nemoda. Ascaris Lumbricoides is widespread in distribution and infects small intestines of pigs and human beings. It may also occur in other organs of the body. The genus Ascaris is the largest nematode parasitic to humans. It is characterized by brownish yellow colour with mouth parts having three lips. The male is about 25 cm long and 0.4 cm in diameter, while te female is about 35 cm long and 0.5 cm in diameter. Mode of Transmission The adult female lays eggs in the small intestine of the host. The eggs are passed out with the faeces and may be swallowed by a new host through contaminated water and food. Contaminated vegetables or fruits which are not washed well before being eaten are also the source of infection. There is also direct infection from faeces to mouth by hand s especially in children. When they are swallowed by a host, the eggs shells are dissolved, releasing the larvae. This penetrates the intestinal walls and enters the bloodstream. They move to liver and then to the heart and lungs. In the alveoli they grow and moult twice. The larvae then migrates up to the trachea where they cause irritation and so are coughed out and so may be swallowed down in to the aeosophogus, stomach and small intestines where they finally mature in adults. Effects of the parasite on the Host During the migration of the larvae they cause irritation in the trachea that lead to lung damage and infection with other diseases. If the is heavy, a lot of is digested food is consumed by the parasite in intestine and this leads o malnutrition in host, especially n children. During their cycle in human host, the parasite feed on blood and therefore can cause anaemia on host. Very heavy infection can also lead to intestinal blockage where victims develop large round stomachs. The worms may also enter the bile duct, pancreatic duct and appendix, causing further complications. Adaptative characteristics of Ascaris lumbricoides to its parasitic mode of life 1. Ascaris lumbricoides has two hosts, human beings and pigs. This ensures that it always has a ready host for survival. 2. It lays many eggs to increase the chance of survival even when some are destroyed. 3. The eggs have protective shell to survive harsh environmental conditions. 4. Ascaris lumbricoides have a thick elastic cuticle which protects it against the digestive enzymes of the host enabling it to survive in the alimentary canal. 5. It has tissues tolerant to low oxygen concentration characteristic of the gut. 6. It has a muscular pharynx through which it sucks digested food from host intestine into its own gut. Prevention and treatment Proper sanitary disposal methods are required especially the availability and proper use of toilet facilities. High standards of personal hygiene should be observed such as washing hands after a visit to the toilet. Hygienic handling and cleaning of fruits and vegetables is necessary. Drinking water should be boiled. Treatment involves use of drugs to kill the worms or inactivate the eggs. Schistomomiasis (Bilharzia) This is a parasite disease of the blood. It is caused by a flatworm of the phylum platyhelminthes of the genus Schistosoma. There are three different species odf the schistosoma that infet human beings. These include Schitosoma mansoni, Schistoma haematobium and Schistosoma japonicum. The parasite is found in fresh water canals, lakes, dams, rice-growing fields and other similar habitats. Modes of transmission The parasite is spread when people drinking water contaminated by larval form called cercariae. Also the parasite can penetrate the skin when bathing or wading through water conatini the larvae. Once in the body they get into the bloodstreams and migrate to the liver where they mature into adults. After coupling of the adult worms, eggs are shed into the blood vessels or alimentary tract. When the faeces or urine containing eggs are disposed of into water, the eggs hatch into larvae called miracidia. The miracidia find and penetrate the water snails such as Biomphalaria and Bulinus. It is from the snails that infective stages cercariae emerge and can now infect human beings who stand, bath or drink in such water. Effects of Parasite on its Hosts The parasite damages the host skin when penetrating and this causes itching. Once in the blood the adult schistosoma releases chemical substances that cause fever. The adult worms have spines which they use to tear through the veins and enter into the intestines or urinary bladder. This causes blood to appear in urine or stool. This can eventually lead to anaemia. The person also experiences abdominal pains and diarrhea. If untreated, the disease can result in death due to exhaustion or by infection from other diseases due to reduced body immunity. Adaptative Characteristic of Schistosoma The parasite has suckers for attachment so that they are not dislodged. The parasite has two hosts, that is the secondary host, the snail and the primary host, the human being. This increases its chances of transfer to several hosts and from one place to another. The cercariae larvae and eggs of the parasite have glands that secrete lytic enzymes which soften tissue to allow for penetration into the hosts. Some larval forms e.g miracidia, are encysted and can remain dormant and viable until they come into contact with a human being. The parasite reproduces through larval forms e.g cercariae, and redia in snails. This makes it very difficult to eradicate the parasite and also increases its chances of transmission and survival. The adult worm in blood produces chemical substances which protect it against the hosts defence mechanism. The worms are of separate sexes. The male form a gynecophoric canal in which it carries the female. This ensures that the e