ENVIROMENTAL HEALTH FOR BSC NURSE-I-IV,GT-2023.pptx

Coc level 1 -4

1. Rift valley University College Harar Campus Introduction To Environmental Health for 2 nd yr. Comprehensive BSc Nursing students By Gadisa T(BSc, MSc) 6/8/2024 By Gadissa T. 1

2. Introduction to environmental Health Learning Objective At the end of this topic the students able to; Understand the basic principle of environmental sanitation, and their importance for health protection Realize the practical techniques in planning, development and maintenance of safe water supplies, and waste disposal facilities. Identify vectors of health importance and introduce appropriate control measures Know the requirements of healthful housing and institutions 6/8/2024 By Gadissa T. 2

3. Introduction To Environmental Health 1.1 Definitions 1.1.1 Health The WHO definition Health has received wider acceptance. “Health is a state of complete physical, mental, and social well-being and the ability to lead a socially and economically productive life and not merely the absence of disease or infirmity” (WHO,1948). There is no single yardstick for measuring health. We are still using indicators of disease (morbidity, mortality) to measure health. Modern medicine is often accused for its preoccupation with the study of disease, and neglect the study of health. 3 6/8/2024 By Gadissa T.

4. 1.1.2 Environment It is the sum of all external conditions and influences (biological, physical, socio-economic, etc) affecting the life and development of an organism, human behavior or society. 4 6/8/2024 By Gadissa T.

5. A. The inner versus outer environment: From the standpoint of the human body, there are two environments: the one within the body and the one outside it. Separating them are three principal protective barriers: The skin/mucous membrane : which protects the body from contaminants outside the body; The GI tract : which protects the inner body from contaminants that have been ingested; and The membranes within the lungs : which protect the inner body from contaminants that have been inhaled 5 6/8/2024 By Gadissa T.

6. B. The personal versus ambient environnent: In another definition, people’s “ personal ” environment, the one over which they have control, is contrasted with the working or ambient environment, over which they may have essentially no control. Although people commonly think the working/ambient environment as posing the greater threat, environmental health experts estimate that the personal environment, often has much more influence on well-being and is influenced by: hygiene, diet, sexual practices, exercise, use of tobacco, chat, drugs, and alcohol, and frequency of medical check- ups, etc 6 6/8/2024 By Gadissa T.

7. C. The gaseous, liquid, and solid environments: The environment can also be considered as existing in one of three forms: gaseous , liquid , or solid . Each of these is subject to pollution, and people interact with all of them particulates and gases are released into the atmosphere, sewage and liquid wastes are discharged into water, and solid wastes, particularly plastics and toxic chemicals, are disposed of on land. 7 6/8/2024 By Gadissa T.

8. Routes of human exposure through the gaseous, liquid, and solid environments. GI Tract Skin AIR Lungs Skin HUMAN BEING GI Tract GI Tract Skin WATER FOOD SOIL 8 6/8/2024 By Gadissa T.

9. D. The chemical, biological, physical and socio-economic environments: Chemical constituents: Contaminants include: toxic wastes and pesticides in the general environment, chemicals used in the home and industrial operations, and 2. Biological contaminants: Include various disease organisms that may be present in: food and water, those that can be transmitted by insects and animals, and those that can be transmitted by person-to-person contact. 9 6/8/2024 By Gadissa T.

10. 3.Physical factors that influence health and well-being: Includes injuries and death occurring as a result of: accidents, excessive noise, heat and cold/weather and climate, the harmful effects of ionizing and non-ionizing radiation. 10 6/8/2024 By Gadissa T.

11. 4. Socioeconomic factors: Perhaps more difficult to measure and evaluate, But significantly affect people’s lives and health. Statistics demonstrate relationships b/n morbidity and mortality and socioeconomic status. People who live in economically depressed neighborhoods are less healthy than those who live in more affluent areas. Factors contributing to the differences range from the unavailability of jobs, inadequate nutrition, and lack of medical care to stressful social conditions, such as substandard housing and high crime rates. 11 6/8/2024 By Gadissa T.

12. 1.1.3. Sanitation: Derived from Latin, “ Sanitas ”, meaning health. It is the establishment of enveromental conditions favorable to health. It is the prevention of diseases by eliminating or controlling the environmental factors which form links in the chain of disease transmission. 1.1.4.Environmental health/ Env’tal sanitation: “It is the control of all those factors in man’s physical environment, which exercise or may exercise a deleterious effect on his physical, mental or social well-being” (WHO). 12 6/8/2024 By Gadissa T.

13. 1.2. Determinants of Health Four basic categories that determine our health: Hereditary or biological factors; Medical care; Life style, and Environment a) Hereditary or biological factors: Major aspects of human biology are controlled by genetics. A person may be healthy in every other way but may have inherited conditions such as hemophilia, diabetes, mental retardation, lack of resistance to disease, etc.   13 6/8/2024 By Gadissa T.

14. B). Medical care: The medical care we receive during our lifetime can determine our health. For example: If a child develops streptococcal infection & does not get medical care, might develop a rheumatic heart condition Two main aspects of health care affect every one: i . Technology: Ever increasing technological advances have added productive years to thousands of lives. ii. A heightened interest in medical self-help: This trend is illustrated by self examination of the skin, breasts, mouth, eyes and nails. 14 6/8/2024 By Gadissa T.

15. C) Life style Life style has a lot to do with one’s health. Lack of sleep and rest reduces our resistance to infections A person who does not exercise enough, and smokes and drinks heavily may develop health problems rather quickly. Of all the health determinants, lifestyle may be the easiest to control. Even so, it will require much effort. D. Environment The environment encompasses the water we drink, the food we eat, the air we breathe. Because of poor environmental management, many people die from environmentally related diseases such as typhoid fever. Some estimates, based on morbidity & mortality statistics, indicate that the impact of the environment on health status is as high as 80%. 15 6/8/2024 By Gadissa T.

16. 1.4. Man-Environment Relationship: This interacting system may be depicted as follows: Man Environment The quality of our life is directly related to the quality of our environment. Concepts of pure water, pure food, Clean air, and clean neighborhood reflected the newer concepts of health as meaning more than the absence of disease. The environment must satisfy not only human physiological needs but also psychological and sociological needs. 16 6/8/2024 By Gadissa T.

17. The quality of the environment through history has been a measure of the character of a civilization “a way of life.” Along with the concepts of “Env’tal health”, there has developed the practice of applying knowledge & science to enhance quality of the environment. Thus, the term Environmental engineering ” has evolved. This is “... that branch of engineering which is concerned with: The protection of human populations from the effects of adverse envi’ntal factors , The protection of the environment, both local and global, from the potentially deleterious effects of human activities , and The improvement of envi’ntal quality for human health and well-being. 17 6/8/2024 By Gadissa T.

18. 1.5. The role of environmental health in public health The role of environmental health is to break the chain of disease transmission. How? To answer this question we must understand the mechanism of disease transmission. For the development of the infectious process, six factors are essential: 1. Etiological/ causative agent 2. A reservoir/source of infection 3. A mode of escape from the Reservoir   4. A mode of transmission from the reservoir to the potential new host ( envin’tal factor) 5. A mode of entry into the new host 6. A susceptible host 18 6/8/2024 By Gadissa T.

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20. Cont . . . These represent a logical sequence of factors/links of a chain , all of which are essential to the development of the infectious diseases. If any one of these links is lacking, disease will not ensue . Expressed in other terms, for a person to get sick from a germ , three conditions must exist simultaneously: An etiologic agent (a germ which causes the disease) A victim (host) susceptible to that disease. A mode of transmission by which the etiologic agent reaches man (the pathway of the agent; i.e. the environment: water, food, air, soil, insects…). 20 6/8/2024 By Gadissa T.

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22. Cont . . . To stop spread (break the chain) of a communicable disease three methods can be applied: attacking the agent, protecting the host or changing/modifying the environment. Environmental management also plays an important role in the control of other non-communicable disease, such as: Health problems arising from chemical poisoning of the air, land and water, occupational disease, etc. 22 6/8/2024 By Gadissa T.

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24. In many disease preventive measures, the attack at the environmental part of the disease cycle (A-H-E) is the most feasible, vulnerable, cheap and sustainable of the three components. It is comparatively more practical, and economical, to control the mode of transmission (the pathway of the germs) from the reservoir (which stores the germ, and which may be a living organism or inanimate, like soil, food, or water) to the potential new host (the living creature, including man, who will receive the germ). Thus the role of environmental sanitation in breaking the chain of disease transmission must be clearly understood. Lever & Fulcrum: The relative position of Environment in the A-H-E triangle. 24 6/8/2024 By Gadissa T.

25. Another way to look at the A-H-E r/ship is from the ecological point of view. Ecology is defined as the r/ship of living things (man included) b/n themselves & with their environment. On the basis of the ecologic concept, the disease agents & man (the host) are always engaged in a constant struggle for survival. Which one will overpower the other depends on the environment in which they interact. This dynamic concept can be illustrated by the familiar principle of the lever and fulcrum . 25 6/8/2024 By Gadissa T.   Host Disease agents ____H____________________________________________A_____ Variable fulcrum position   Environment (E)

26. Levels of disease prevention 6/8/2024 26 There are three levels A. Primary prevention : this is protection of healthy people from becoming sick - It is prevention of disease by altering susceptibility or reducing exposure for susceptible individuals The objectives are health promotion, prevention of exposure and prevention of disease

27. 6/8/2024 27 1. Health promotion : consists of general non-specific interventions that enhance health and the body’s ability to resist disease. ‘promotion is defined as the process of enabling people to increase control over, and to improve, their health’. 2. Prevention of exposure : such as the provision of safe and adequate water, proper excreta disposal, vector control, safe environment at home, at school, at work and on the streets.

28. 6/8/2024 28 3. Prevention of disease: during the latency period between exposure and the biological onset of disease e.g. immunization, chemoprophylaxis . Active immunization: means exposing the host to a specific antigen against which it will manufacture its own protective antibodies after an interval of about three weeks (during which the immunized person remains susceptible to the disease);

29. 6/8/2024 29 Passive immunization: means providing the host with the antibodies necessary to fight against disease. - is commonly given after exposure has occurred (as in the case of exposure to rabies or tetanus) Both forms of immunization act after exposure. However, for active immunization to be protective, the timing of its administration must be at least three weeks prior to exposure

30. 6/8/2024 30 B. Secondary prevention : After the biological onset of disease, but before permanent damage sets in. Objective: to stop or slow the progression of disease so as to prevent or limit permanent damage, through the early detection and treatment of disease. C. Tertiary prevention : After permanent damage has set in, Objective: - to limit the impact of that damage: The impact can be physical, psychological, social (social stigma or avoidance by others), and financial. - Rehabilitation refers to the retraining of remaining functions for maximal effectiveness, and should be seen in a very broad sense, not simply limited to the physical aspect.

31. Introduction to safe water supply “Whoever wishes to investigate medicine properly should consider the seasons of the year, the winds and the waters in relation to health and diseases”.      Hippocrates 460-354 B-C. 31 6/8/2024 By Gadissa T.

32. 2.1. Introduction…………… Water is a basic necessity of life. Man, animals and plants cant not survive without water. We can live for sometime without shelter, clothing, and even without food. But without water a person soon perishes. Definition of Terms: A. Raw water Untreated water from suspicious sources: surface waters like rivers, lakes or from unprotected wells and springs B. Contaminated water Water containing harmful MOs or toxic chemicals which make it unfit for use. Generally these contaminants can not be detected by the organs of sight, taste and smell. 32 6/8/2024 By Gadissa T.

33. Cont . . . C. Polluted water Water that has come in contact with substances that alter its physical qualities, so that it changes in color, level of turbidity, taste or smell . Pollution can be detected by the sense organs. D. Clear water Water that has a sparkling appearance to the eye. It may be clean or contaminated E. Clean water Water that is free of disease causing organisms   6/8/2024 By Gadissa T. 33

34. F. Palatable Water Water which is pleasant to drink (has good taste). It is not necessarily clean or potable. It can be pleasant to drink, but may be contaminated. G. Potable water This is drinkable water. Water which is free at all times from pathogenic organisms or chemicals. 34 6/8/2024 By Gadissa T.

35. 2.3. Water Resources of the Earth Water is the most widely occurring substance in the world . The amount of water found in the oceans and seas is about 324x10 6 miles 3 . The polar ice-caps carry about 6.7x10 6 miles 3 . Over 72% of the earth’s surface is covered by water . If the body of water on earth could be evenly distributed, it could cover the globe to an average depth of 4 kms. 97% of the total water coverage is not immediately available to human use . This is because: Sea water contains 36 grams of salt/ liter and The polar ice-caps (that cover about 2% of all the water body) is far away. 35 6/8/2024 By Gadissa T.

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37. Useful water of the earth is only about 1.6x10 5 miles 3 : This is about 0.8% of the total. This again is neither evenly distributed nor properly used. In some regions it is abundant and properly utilized, While in some other it is wasted and polluted, and In the remaining regions it is scarce or completely lacking . 37 6/8/2024 By Gadissa T.

38. 2.4: Some important properties of water Pure water consists of two atoms of hydrogen and one atom of oxygen chemically combined = H 2 O It boils at 100 C and freezes at O C at sea level . Pure water is practically colorless, odorless and tasteless . Any deviation form these physical characteristics are indicative of its impurity. 38 6/8/2024 By Gadissa T.

39. Cont . . . Water has also a very high molecular attraction both for: its own molecules (cohesion) and for molecules of other substances (adhesion). Exists in 3 states : liquid, solid and gas (vapor) In its liquid state weights approximately 830 times heavier than air. In its gaseous (vapor) state it is approximately 133 times lighter than air, thus, it rises in the atmosphere to form clouds. 39 6/8/2024 By Gadissa T.

40. Cont . . . Water reaches its highest density at 4 C . This is an important ecologic factor for the existence of fish when water freezes at the surface. The liquid water beneath ensures fish survival. Water has the ability to dissolve solids and to absorb gases and other liquids; Hence it is often referred as the “ Universal solvent ”. 40 6/8/2024 By Gadissa T.

41. 2.5. Importance of Water Water and life: The normal functioning of the human body depends entirely on adequate quantity of water. About 75% of bacterial cell is water. About 70% of the human bodyweight is water. To maintain this level, we require a minimum of 2 liters of water per day. Water is essential for health and sanitation. Most of the foods we eat contain water. For E.g Milk= 88% ,Meat = 60%, Egg = 66%,Fish = 80% Potatoes = 75% water 41 6/8/2024 By Gadissa T.

42. Cont . . . It is principal raw material for food production , Is essential in our ecology: The atmosphere surrounding us contains an enormous quantity of moisture. Essential to run industry: Coal mining, brewery, tannery , etc. Source of energy: Generating hydro- electric power , Useful for recreation , fishery and aquatic wealth , navigation, etc.. 42 6/8/2024 By Gadissa T.

43. Water and man’s Progress: Water is the root of human civilization. Ancient civilizations grew where abundant water supply was available: the Nile-Egyptian , Tigris & Euphrates- Babylonian , Indus & Ganges-Indian and the Yangtze Kiang- Chinese civilizations. Large cities are also located where abundant fresh water is plentiful, for example London, Dublin, Cairo. Even the establishment of A.Ababa is related to the abundance of adequate water supply at Finfine . 43 6/8/2024 By Gadissa T.

44. Water and industry: Nearly all industries are water thirsty (for cooling, waste transport, processing, etc.) About 10 liters of water is needed to produce a liter of petrol. About 40 liters of water required to produce a can of vegetable. About 100 liters of production of a kg of paper About 600 liters for production of one kg of woolen cloth About 3500 liters of water is required to produce one kg of dry cement. 44 6/8/2024 By Gadissa T.

45. Cont . . . Thus, the availability of plentiful supply of water is one of the basic requirements to develop the natural resources of a country- agriculture, industry or hydro- electric power. Water is more than a public utility. It differs from others in that its shortage or impurity endangers the life of the community. 45 6/8/2024 By Gadissa T.

46. Water and Disease: Water from contaminated sources causes numerous diseases and untimely deaths. The fact that man needs water and can not survive without it forces him to use it even for drinking purposes from any sources (clean or contaminated). This leads for many people to surfer or die form water-borne diseases. 46 6/8/2024 By Gadissa T.

47. Diseases associated with water: Water-related diseases can broadly be classified into five epidemiological groups: Group I: Water-borne disease : Basically water is used as a vehicle for transmission and the pathogen is in the water e.g. Cholera, typhoid, infectious hepatitis, etc. Group II: Water-shortage (washed) diseases: Quantity matters e.g. Skin infections (scabies), eye diseases (trachoma). Group III: Water-based (contact) diseases: The pathogen spends part of its life cycle in water snail or other aquatic animals e.g. schistosomiasis, guinea-worm Group IV: Water-arthropod -related diseases e.g. malaria, onchocerciasis Group V: Chemical constituents in water either in excess or shortage e.g. fluoride 47 6/8/2024 By Gadissa T.

48. Skeletal fluorosis 48 Dental fluorosis Fluoride Problem 6/8/2024 By Gadissa T.

49. 49 Fluoride level (mg/L) Chronic health effects Nil Limited growth and fertility 0.0-0.5 Dental caries 0.5-1.5 Promotes development of strong bones and teeth, prevents tooth decay 1.5-4.0 Dental fluorosis (mottled teeth) 4.0-10.0 Dental fluorosis, skeletal fluorosis >10.0 Crippling fluorosis, possibly cancer Table. Effects of fluoride ingestion from water on human health (Dissanayake, 1991). 6/8/2024 By Gadissa T.

50. 2.6. Water and its relationship to Environmental Health: It is impossible to have a sanitary environment without water . Health can not be maintained without adequate and wholesome water supply. The provision of a good, clean, plentiful water supply in a community is of vital importance in public health services. The currently (Sept.2013) launched WASH project initiative is thus with the aim to avail 90% safe water supply to all communities in Ethiopia. 50 6/8/2024 By Gadissa T.

51. Cont . . . Community water supply should fulfill three important criteria to be wholesome: Safe in quality Ample in quantity (adequate) and Accessible in terms of distance, and affordability (cost: it must be cheap). The best accessible water is a tap within the room where it is needed. The global (WHO recommendation) initiative for safe water supply is to avail water to a community in at least an average walking distance of 15 minutes . 51 6/8/2024 By Gadissa T.

52. 2.7. Water Requirement (demand) The demand of water depends on the standard of living and degree of culture as well as for what purpose it intended. The demand can be grouped under the following categories of purposes: 1. Domestic purposes: Drinking, cooking, bathing, washing the hands, etc. 2. Civil or public purposes: Road washing, fire control, garden, etc 3. Industrial purposes: Factories, power plants, etc. 4. Business or trade purposes: Recreation, bottling, etc. 5. Loss and waste. 52 6/8/2024 By Gadissa T.

53. For example the total water requirement of a community/ an institution/ household etc. can be calculated as shown below: Purpose Liters / head/ day 1. Domestic: Drinking-----------------------------------2 Cooking -----------------------------------5 Bathing ----------------------------------35 Washing hands--------------------------8 House hold sanitary purposes-----50, etc 2. For domestic animals to drink: Hens Donkey, etc. 3. For industrial purposes: Machinery washing Floor washing Engine cooling, etc. 4. For recreation, etc , 53 6/8/2024 By Gadissa T.

54. 2.8. Sources of water Hydrologic Cycle: The ultimate source of all our water supply is rainfall. The constant movement of water from clouds to earth and back again is known as the hydrologic cycle or water cycle . The deriving source for this cycle is the sun’s energy as heat. 54 6/8/2024 By Gadissa T.

55. Cont . . . Through the hydrologic cycle we can locate all the water exiting in the world. All the water that are found on the surface of the earth are constantly circulating, and as they move change constantly their phases: liquid, ice (solid), gas (steam/ vapour ). The different phases of rainfall are known collectively as precipitation . In nature, the sources of water for human uses are four: Ground water : wells and springs Surface water : rivers, streams, lakes, dams, ponds, etc Rain water : collected over impermeable/ non-absorbent surfaces. Sea-water after removing the salt through desalination by the process of distillation. 55 6/8/2024 By Gadissa T.

56. 2.9. Impurities of Water Pure water is not found in nature . Water gathers impurities as it goes through its natural cycle: it absorbs dust & gases like CO 2 from the atmosphere. On the ground surface , it is exposed to pollution by organic and non organic matter including human excreta. As the water percolates through soil/rock, it dissolves and carries with it various minerals, the amount depending upon the distance of percolation and the mineral composition of the soil. As percolation continues, the original suspended impurities, including MOs, tend to disappear, until the water which is obtained from deep wells may be expected to be free from all impurities except those dissolved 56 6/8/2024 By Gadissa T.

57. The common impurities of water can be listed as follows: Entrained gases : CO 2 , CH 4 , nitrogenous & organic compounds. Dissolved minerals : Ca, Mg, Na, Fe, Mn and their carbonates, hydroxides, chlorides, sulfates, fluorides, nitrates and silicates; alkyl benzone sulfonate from detergents, & synthetic organics from insecticides and pesticides. Suspended & colloidal materials : Bacteria, algae, fungi, protozoa, silt & coloring such as from plant dyes. Radioactive materials : Radioactivity imparted by contact with radioactive sources: mining/ processing of ores or industrial radioactive wastes. 57 6/8/2024 By Gadissa T.

58. 2.10: Consideration in planning a community water supply program: Primary considerations for developing water sources to communities should ensure: The quality of the water supply will be safe and wholesome . The quantity of the water supply will be adequate and continuous for liberal use. Convenience : The water should ideally be piped, and therefore, easily accessible to individual house holds, and it should be reasonably cheap. Therefore, primary considerations in developing sources of water include: Determining amount and quality of the water needed. Find and develop a source /sources which will supply the needs of the community. The sanitary measures (protection & treatment) to be employed. 58 6/8/2024 By Gadissa T.

59. 2.11. Quality of Water Any new sources of water should be tested for quality before expensive work is undertaken. Good quality water for human use should be: Colorless Sparkling and cool, and Free of harmful MOs, sediment, objectionable minerals, tastes, & odor. Therefore, the following tests should be performed before developing potential water supply source and after its development at regular intervals: Testing for contamination Testing for minerals/chemicals Testing for sediments, color, taste, odor, acidity & alkalinity. 59 6/8/2024 By Gadissa T.

60. 2.12:Locating and developing adequate sources of water supply Ground/underground water: Ground water is that portion of the rainfall that has percolated into the earth until stopped by impermeable stratum. It can be abstracted through wells and springs. 60 6/8/2024 By Gadissa T.

61. Advantages of ground water: Comparatively free from disease causing organisms. Does not need further treatment after initial treatment during protection. It can be found near a family or a community. It is not exposed to evaporation Disadvantages: It normally needs pumping unless from a spring. In certain localities may contain excessive dissolved minerals. 61 6/8/2024 By Gadissa T.

62. 2.13. Development of ground-water: In terms of depths of the water bearing stratum, ground- water may be tapped by: Shallow wells , Deep wells, Artesian wells/ springs and Springs. 1. Shallow wells: Are wells dug into uppermost permeable stratum only. The maximum depth considered is up to 30 meters. They are dug with locally available manual equipments. Shallow wells may not usually yield dependable amount of water 62 6/8/2024 By Gadissa T.

63. 2. Deep wells: Are wells sunk into 2 nd or below impermeable stratum. Are sunk by drilling machines. Have depths over 30 meters. 3. Springs: Are occurrences of ground water naturally issuing (outcropping) at strategic points. 63 6/8/2024 By Gadissa T.

64. 4. Artesian wells/ springs: Are wells where ground water gushes out on its own accord. They need no artificial effort. They are found where there are spectacular ground formations. 64 6/8/2024 By Gadissa T.

65. 2.14. Protection of ground water from contamination: The techniques of protecting groundwater from contamination are based on good knowledge of: Geology, Topography, Drainage basin, Vegetation, and The human habitation of the locality. The rate of contamination of ground water by pathogenic MOs or by dangerous chemical pollutants depends on the following factors: The nature of the aquifer: particularly permeability of the ground formation. The depth to the water table: if the water table is high, less chance for the pathogenic organisms to be filtered. Distance from the source of contaminants (e.g. latrines). 65 6/8/2024 By Gadissa T.

66. Cont . . . MOs do not move in soil on their own accord. They should be carried horizontally or vertically by fluids (seeping water, rain, urine, sewage). Many experiments have indicated the depths intestinal bacteria can be carried in the soil: The travel of intestinal bacteria in dry soil is practically nil . Accompanied by leaching fluid (water) the distance traveled varies with the porosity of the soil. In soils of reasonable porosity the avg. maximum travels are: 60cms vertically & 30cms horizontally. However, in areas having cracks/ crevices, or limestone formations the length of travel is unlimited both vertically and horizontally. Dissolved chemical pollutants also travel unlimited distances in the soil 66 6/8/2024 By Gadissa T.

67. Prevention of Contamination of a Well: 1. Proper sitting of the well: Sited uphill on a higher level form a source of contamination (latrines). The hydrolic gradient should be from the well towards the latrines ; and never vice versa. In normal soil formations, the minimum distance of 15 meters from source of contamination (latrines). 67 6/8/2024 By Gadissa T.

68. 2. Protection of the well: Building the inside wall with waterproof cement masonry to a minimum depth of 3 meters from the mouth of the well. The water proof wall has to be extended to minimum of 60cm above the surface. Surrounding of the well should be graded off to prevent flow of storm into the well. Cover: A concrete cover overlapping the casing to prevent entry of any form of contaminants into the well. 68 6/8/2024 By Gadissa T.

69. Cont . . . Ideally a pump should be used to draw water from the well without contaminating it. The immediate area of the well should be fenced to keep animals away. A diversion ditch should be constructed to 15 meters around to divert flood coming into the well. 69 6/8/2024 By Gadissa T.

70. 2.14.3: Surface Water Surface water is never clean since it collects wastes as it slides over the earth’s crust. The pollutants may include: Human and animal wastes or Toxic effluents from industries. Agricultural runoffs containing toxic chemicals: herbicides, pesticides, fertilizers. Soil, in the form of silt. In any way, surface water should never be used as a source of water supply without treatment. 70 6/8/2024 By Gadissa T.

71. Rain Water Contamination of rain water: From the sanitary point of view, rain-water may be the purest of all sources of water in nature. Nevertheless, it is exposed to contamination under the following conditions: As it falls through the atmosphere picks contaminants like gases, dust, particulates, soot, plant pollen, bacteria, etc. As it touches the collection surface, its purity depends on the cleanliness of this surface. It may be contaminated during storage, distribution and handling. Thus its protection basically aims at eliminating the above three ways in which it is likely to be contaminated. 71 6/8/2024 By Gadissa T.

72. Sanitary roof catchments to collect rain water This is a method of collecting rain water from a roof The first 10 to 15 minutes of the rain water washes off the dirt on the collecting surface. This should be made to flow into a waste drain tank or routed to be flushed out. After this tank is full the clean rain-water is made to flows into a collection tank. An alternative method is to pass the rain water form the drop pipe though a sand filter. 72 6/8/2024 By Gadissa T.

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74. 1 st flush 74 6/8/2024 By Gadissa T.

75. Surface water treatment for municipal water supplies (Large scale treatment) Objectives for Water Treatment: Water treatment may be defined as the process of removing all those substances (biological, chemical or physical) which are potentially dangerous or undesirable in water supplies for human and domestic use . Surface waters are never pure; therefore, deserve adequate treatment if they are intended for domestic purposes. 75 6/8/2024 By Gadissa T.

76. Thus, the main objectives for water treatment are: To remove pathogenic organisms and prevent water-borne diseases. To remove substances which impart color, taste, or odor to the water. To remove excess or undesirable chemicals or minerals from the water. To regulate essential elements or chemicals (remove excess, limit amount or remove unwanted): E.g fluoridation/ de-fluoridation or water softening. To remove excess or undesirable dissolved gases. To achieve the above objectives, water treatment procedures may involve: simple physical processes like sedimentation or complex physico -chemical and biological processes depending upon the impurities observed in the raw water that need removal. 76 6/8/2024 By Gadissa T.

77. The following figure depicts the ideal steps of a typical municipal water treatment process. Pumping station Aeration and or Pre-chlorination basin Basin for applying coagulation Mixing basin Sedimentation basin Filtration (slow or rapid sand filter) To distribution system reservoir Surface raw water source: lake, pond, river Post- chlorination Distribution 77 6/8/2024 By Gadissa T.

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79. Treatment of water on a small scale For economic reasons, large scale water treatment is not practical for poor communities. However, water-borne diseases are prevalent among such communities because of consumption of untreated water. Generally, water for human use is collected from various unprotected sources, and is consumed without treatment. Water must be adequately treated before consumption, even in rural areas . 79 6/8/2024 By Gadissa T.

80. Treatment of house hold water supplies may be achieved by the following methods, used singly or in combination. Boiling: Is one of the most reliable methods of disinfecting water on a small scale if boiled 15-20 minutes. All forms of microorganisms including the most resistant spores or cysts can be destroyed using this method. 2 . Filtration : Using sand filters or candle (ceramic) filters. Sand filters are of two kinds; slow and rapid sand filters. Rapid sand filters are usually used for large scale water treatment and the mechanism is physical straining by the sand particles. The slow sand filter can be home-made or a large scale. In the slow sand filtration technique the mechanism is similar in both the home-made and the large scale filtration. 80 6/8/2024 By Gadissa T.

81. The filtering medium in the slow sand filter is the sand as a physical straining method and biological activities due to growth of microorganisms which takes place in the top most layer of the sand grains soon after the filter is put into operation. The microbial growth in the sand grains forms a stick gelatinous coat in the top layers of the filer, and is called schmutzdecke , a German term meaning “cover of filth”. This filter may be made for home use with barrels (drums). However, the sand filter can not be relied upon to remove organisms like viruses and some of the very small sized bacteria. 81 Cont . . . 6/8/2024 By Gadissa T.

82. Candle filters are commercially made for filtering individual water supplies. The core of the filter is a porous cylinder (shaped like a wax candle, hence the name), made from high-quality porcelain. The efficiency depends upon the pore size of the candle. Different manufactures produce candle filters of varying pore sizes, but generally the pore size varies from a maximum radius of about 50 microns to a minimum radius of 0.3 micron. A micron is one millionth of a meter. The average size of a bacterium, however, is about 1.5 micron ; thus the filters having larger pore sizes may not remove all the pathogenic organisms ( e.g viruses). Another limitation of this apparatus is its cost which may not be affordable by many families. These days there are also other modern filters like carbon filters and others. 82 6/8/2024 By Gadissa T.

83. 3. Chemical disinfection: Chemical disinfection compounds such as chlorine, iodine, silver salts and potassium permanganate etc., may be used. Chlorine or its compounds are however cheaper and commonly available. 4. Storage and sedimentation: Water is not a suitable medium for the survival of microorganism including that are pathogenic. But water serves as a vehicle of transmission. Therefore, storage of water for more time and sedimentation activities will kill or remove microorganisms and can make water safer for domestic use. 83 6/8/2024 By Gadissa T.

84. 5. Exposure to sun-light: Exposure to Ultra Violate light radiation (UV-radiation) kills microorganisms. UV light is a known disinfectant. It is demonstrated that water for drinking can be exposed to light in transparent plastics/glass for given periods to make it safe for drinking. 84 6/8/2024 By Gadissa T.

85.   3. Community Waste Disposal 85 6/8/2024 By Gadissa T.

86. Introduction The problem of wastes is becoming a global concern. Wastes may have effects on house-hold levels, at a community level, at a national level and may also have cross border problems, becoming concern of the international community. This chapter will briefly discuss the public health aspects of community wastes. Waste is anything that is normally discarded as useless or unwanted. Wastes are mainly results of human activities including physiological (as feces and urine) and daily activities performed for survival and development of the society.   6/8/2024 By Gadissa T. 86

87. Group of Wastes Wastes can be grouped into four large classes: Solid wastes Liquid wastes Gaseous or particulate wastes and Energy wastes In this course we will look to some details of the solid and liquid wastes. 87 6/8/2024 By Gadissa T.

88. Solid wastes:   These are materials which are solid in nature which arise from various human activities and which are normally discarded as useless or unwanted. These wastes may be homogenous masses such as agricultural wastes or wastes from specific factories/industries or those that are heterogeneous masses from residential or other commercial centers. Increase in population and the advances in technology lead to the increase in amount and complexity of the wastes produced. In Ethiopia litters are thrown indiscriminately every where. Such acts have aesthetic, health and economic impacts. The bubonic plague (Black Death) epidemic that wiped out about half of the population of Europe in the 14 nth century was the result of such indiscriminate accumulation of solid wastes that lead to proliferation of rats with their attendants, the fleas, that carry the bubonic plague. 88 6/8/2024 By Gadissa T.

89. Liquid waste: Liquid waste is that part of community waster supply after it has been fouled by filth in a variety of uses. The fouling may include contamination with feces and urine. Liquid waste may include the following: Domestic /sanitary waste water from residential, institutional and business areas. Industrial waste water. Storm/rain run off. Combined waste water-combination of the above. 89 6/8/2024 By Gadissa T.

90. Solid waste Management Definition of terms: Refuse: Any thing thrown away. This is solid waste which includes all combustible or non-combustible / putrecible and non- putrecible wastes with the exception of excreta. Rubbish : Non- putrecible solid waste which is combustible or non combustible except ash. e.g. Broken glasses, paper wastes, plastics… Ash : Burned residues. 6/8/2024 By Gadissa T. 90

91. Cont . . . Garbage: Food waste ( putrecible ). Mixed or separate wastes produced during use, preparation, storage, or processing of food such as leftovers, peel etc. Pathological wastes: are wastes that include human tissues and dead animals. These are considered as infectious. Infectious wastes: Wastes that carry pathogens and includes pathological wastes and materials soiled with blood, or body fluids. e.g. syringes, needles, gauzes, gloves, etc. 6/8/2024 By Gadissa T. 91

92. Cont . . . Agricultural wastes: residues from farms (crop residues), farm animal manure, fertilizer containers, crop products, pesticide containers, etc. Special wastes : These are wastes that may be hazardous. Includes for example, chemicals, petroleum and paint products and residues from pollution control devices etc.. Junk wastes : This includes appliances, junks of old refrigerators, cars at backyards, etc. Industrial wastes : Wastes from industries and may include hazardous materials, organic and inorganic residues, wood and paper products, etc. Demolition wastes : Wastes from construction sites and buildings that are demolished. 92 6/8/2024 By Gadissa T.

93. Functional elements: Various activities associated with solid waste management from cradle to grave (generation to disposal). The functional elements in solid waste management are six: Waste generation Waste storage Waste collection Waste transfer or transport Waste processing and recovery and Waste disposal 93 6/8/2024 By Gadissa T.

94. Objectives of solid waste management: Is the proper planning, organizing and implementing of handling, storage, collection, transport, recovery and disposal of waste; thus to minimize and prevent its effect on health, conserve resources and enhance preservation of the environment – land (soil), water and air. The modern concept in solid-waste management is to dispose off as small amount of waste as possible by means of recovery, recycling and re-use. In other words it means wastes are valuable resources that can be used. 94 6/8/2024 By Gadissa T.

95. Public health importance of solid wastes: Problems of improper handling of solid waste include the following: Serve as breeding site for flies, rodents and other animals. This leads to disease transmission and property damage. Ecological impacts on: Water: putrecible organic and biological matters Soil: Hazardous wastes Air: Incineration gases, dust. Adverse effects on land and property value : The land can not be used. Fungus from the waste destroys property. Public nuisance : dust, odor, stray animals, bad sight… Inability to re-use or recycle materials result in unnecessary waste and depletion of natural resource. 95 6/8/2024 By Gadissa T.

96. Management of solid waste: Management of solid waste may be defined as the process by which workable alternative programs and plans are developed to solve problems of solid waste. In all solid waste management systems the focal points are the six functional elements : Generation–Disposal.  Cavemen and early civilizations did not have problem with waste because it consisted mainly of organic waste and the decomposers converted it into useful material (humus). The two basic facts in the ancient societies for solid waste to pose little impact were: less population in large area (population space ratio) and less complexity of the waste. When people were few they generated little waste, and land was not a problem (large space was available to dump waste). 96 6/8/2024 By Gadissa T.

97. Cont . . . The problem became magnified with more people generating more and a variety of waste: pathogenic, chemical, liquid, solid, nuclear, and hazardous. Little of this waste is food for the decomposers. E.g : plastics are not decomposed by Mos. Thus, a variety of methods must be used to manage the waste. 97 6/8/2024 By Gadissa T.

98. On-site handling of waste: On-site handling refers to activities associated with handling of solid waste until placed in containers for storage before collection. This includes handling, storage, processing and separation at the source . Separation of waste component is an important step in the handling and storage of solid waste at the source. The best place and simple to separate waste material for re-use and recycling is at the source of generation. On-site storage of solid waste in the most proper manner is the beginning of disposal. Improperly kept or simply dumped wastes are sources of nuisance, flies, smells and hazards, so are wastes that are not properly stored in the generation areas. 98 6/8/2024 By Gadissa T.

99. There are four factors considered in the on-site storage of solid waste: The type of storage container to be used : It should be durable, easily cleanable, easy to handle, wet proof and with proper covers. The location where the container is to be kept : in front of the house, at the back, etc. Public health and aesthetic considerations : Is it infectious, the need for cover, does it smell, etc.. The collection method, time and condition : Is there direct hand touch? When is it to be collected? Is it wet or dry, etc. 99 6/8/2024 By Gadissa T.

100. Onsite processing of solid waste: The objectives of on-site processing are: To reduce volume of wastes generated. To alter the physical form (e.g. shredding, chopping, grinding, etc. To recover usable materials (salvaging). The methods of processing include: Grinding the waste (Volume reduction, and altering physical form) Sorting the waste (Recovery) Shredding the waste (Volume reduction) Composting (Conversion to a useful material) Incineration (Volume reduction) Compaction (Size/volume reduction). 100 6/8/2024 By Gadissa T.

101. Collection of solid waste: The generation of residential, commercial and industrial solid waste is a diffuse process that takes place in every home, every operational building and every commercial or industrial facility as well as in the streets, markets, parks, offices, institutions, vacant lots, etc. of every community. As the generation pattern is more wide-spread and the total quantity and complexity increases; the logistic or transportation problem associated with collection becomes more complex and expensive. 101 6/8/2024 By Gadissa T.

102. It demands experienced/skilled people to manage. It demands special vehicles. It demands more manpower and hand tools. It demands more monetary expenditure for fuel, salary and maintenance. This makes solid waste collection the most expensive compared with other operation and management procedures. In most cases collection takes 60-80% of the operational cost in waste management. 102 6/8/2024 By Gadissa T.

103. There are 5 areas of focus to notice in planning collection of solid waste: Consider the different types of collection systems and adopt what is appropriate and practical. Consider the equipment and labour requirement. Analyses collection system including component composition. Study the methods involved in setting up collection routes. Consider advanced techniques and technologies that can be used to evaluate collection operation. 103 6/8/2024 By Gadissa T.

104. Collection service of solid waste Collection includes the following: Gathering or picking up the solid waste from the various sources. Taking the collected wastes to the location where it will be emptied. Unloading of the collection vehicle. Solid waste should be collected preferably not more than every three days. The collection frequency is based on the life cycle of the housefly and the production of odor due to the decomposition of organic matter. Under ideal conditions a housefly develops from an egg into an adult in about 8 days . These flies breed in refuse. 104 6/8/2024 By Gadissa T.

105. Cont . . . Collecting and disposing of the solid waste within 8 days, interrupts the flies` life cycle. By collecting refuse in a timely manner, people can control fly population to a large extent. Waste also provides food and harborage for other insects, as well as rodents capable of transmitting diseases to humans. Combustible materials too, may build up and increase the chance of fire out-break. 6/8/2024 By Gadissa T. 105

106. Residential collection of solid waste: There are different methods of solid waste collection from residential buildings (areas): Kerb collection: The home owner is responsible for placing the waste container to be emptied at the kerb (road-side) on collection day and for returning the empty container. Alleys collection: This is arranged between the owner and the collection crew (optional). Set-out collection: Waste container taken (collected) by crew and the owner is responsible for returning the emptied container. Set-out set-back: Collection and return of waste container all done by crew. Back yard carry service : Collection crew that go along with the collection vehicle are responsible for bringing out stored solid waste from the back yards of dwelling units and replacing empty containers in place. 106 6/8/2024 By Gadissa T.

107. Disposal of solid waste After all efforts are put on making use of solid wastes either by recovery, reuse or recycling something must be done with the solid wastes that are collected and of no further use. There are two alternatives for the disposal of solid wastes: Disposal on or in the earth’s surface. Disposal under the sea or ocean. 107 6/8/2024 By Gadissa T.

108. Methods of disposal on land Open dump Controlled tipping Sanitary land fill Secured land fill Composting Incineration 108 6/8/2024 By Gadissa T.

109. Open dump: This is land disposal site where solid wastes are deposited and left uncovered; with little or no regard for control of scavengers, aesthetic, disease, air pollution and water pollution problems .   B. Controlled tipping This is a slightly upgraded version of an open dump. The waste is intermittently covered with a layer of earth; hence has reduced pollution hazard on the surface. Advantages: Easy to manage Low initial investment and operational costs. Can be put into operation in a short period of time. Can receive all types of waste. 109 6/8/2024 By Gadissa T.

110. Disadvantages: If it is not properly managed it can show the following drawbacks. Unsightly Breeding of disease causing pests Foul odor Causes air pollution if wastes get on fire. Can contaminate ground or surface water through leachets and runoff. 110 6/8/2024 By Gadissa T.

111. C. Sanitary landfill This is a land disposal system in which the wastes to be disposed are initially packed and compacted, placed in the landfill, and covered with a layer of soil at the end of each day’s operation. The daily operation also contains compaction of the covered waste. At the completion of the disposal operation a layer of 60 cm of earth cover will be applied and finally compacted. 111 6/8/2024 By Gadissa T.

112. Advantages of sanitary landfill: Economical if land is available Low initial investment Complete final disposal method as compared to incinerator or composting. Can receive all kinds of waste. Sub marginal land may be reclaimed for various purposes. If properly designed and operated can minimize problems of pests, air pollution, aesthetic, water pollution and problems of scavengers. May be used to generate energy from biogas. If properly designed, fulfills the public health considerations, it has options for resource recovery and production of energy. 112 6/8/2024 By Gadissa T.

113. Disadvantages: Land may not be available in populated areas. Proper sanitary landfill standard must be adhered. Needs periodic maintenance. If located near residential area it may provoke public opposition. Explosion may occur due to methane gas accumulation. Gases produced may become nuisance. Requires special design and construction including special equipment. If not properly constructed leachets may become a problem. 113 6/8/2024 By Gadissa T.

114. D. A Secured land fill This is a specially engineered design where hazardous wastes are buried in concrete boxes in a very controlled and managed manner; and the area is fenced and specially marked with warning signs of hazard. E . Composting is a method /process by which organic wastes are changed by the action of microorganisms into humus (stabilized final product of decomposition) which is something a useful matter for soil conditioning. It is a method of waste reduction and resource recovery. Composting may be achieved by aerobic or anaerobic process. However, the anaerobic process produces a foul smell. 114 6/8/2024 By Gadissa T.

115. Advantages: Destroys pathogenic microorganisms and parasites due to unfavorable environment, and heat. It is simple and useful method of solid waste disposal. Disadvantage /Limitation: Fly breeding F. Incineration: Incineration is a process of burning combustible components of refuse in a controlled and sanitary manner. This requires the need to separate the combustible waste from the non-combustible. The residues of incineration (ashes) can finally be disposed into landfills. Infectious solid wastes from health institutions (hospitals, health centers, clinics, etc ) and research laboratories can effectively be removed by incineration. 115 6/8/2024 By Gadissa T.

116. In some countries dead bodies (human corpse) are removed by incineration normally called cremation. Tissue wastes from operation rooms, placentas from delivery rooms, etc. may be removed as such; however, some cultures and governmental rules may not allow incineration of bodies and tissues. Disposal of solid wastes by incineration can effectively be carried out in small scale in food catering establishments, schools and other institutions. Daily generation should be incinerated on daily bases. A sanitary incinerator should be well organized to attain the following advantages: Less land is require., A central location is possible for short haul distance. 116 6/8/2024 By Gadissa T.

117. Cont . . . The ash and other residues are practically free of organic matter and nuisance. Many kind of refuse can be burned; even the non-combustible materials are reduced in bulk. Climate or unusual weather does not affect it. It can be flexibly operated; 8, 16 or 24 hours per day. The disadvantages are Requires initial investment (has initial cost). Operating cost relatively high and skilled workers required for its operation and maintenance. May require fueling to initiate incineration of wet wastes. 117 6/8/2024 By Gadissa T.

118. Liquid Waste Management 6/8/2024 By Gadissa T. 118

119. Introduction Liquid waste is part of a community water supply after it has been fouled by a variety of uses. The liquid waste may also be fouled by human excreta which is a source of enteric diseases. The collection and safe disposal of human waste including liquid waste and human excreta is among the most important problems of environmental health. 6/8/2024 By Gadissa T. 119

120. Public health importance of liquid waste including human excreta: Untreated liquid waste including human excreta if accumulated and if not properly disposed off will create the following public health problems: Produces malodorous gases. May serve as a breeding site for various insects and rodents. May contain numerous pathogenic organisms and ova of parasites that dwell in the intestinal tract. Contains nutrients which encourage growth of aquatic plants which may lead to eutrophication (nutrient rich) of water bodies. 120 6/8/2024 By Gadissa T.

121. Cont . . May carry toxic chemicals that have adverse effects on health, water and soil. May lead to pollution of water bodies’ devoid them their natural aquatic life due to lack of dissolved oxygen (DO). Leads to contamination of ground and surface sources of water supplies. Creates intolerable nuisance. In many cities, towns and rural communities of Ethiopia, today people live and raise their children in highly polluted environment especially with human excreta. Urban and peri-urban areas are among the worst polluted and disease ridden habitats. 121 6/8/2024 By Gadissa T.

122. Cont . . Much of this pollution, which leads to high rates of disease , malnutrition and death , is caused by lack of adequate excreta and liquid waste disposal facilities and services. As communities expand with population increases, environmental pollution grows worse and the need for safe, sustainable and affordable sanitation technology or system becomes more critical. 122 6/8/2024 By Gadissa T.

123. Definitions of terms Excreta: Waste matter eliminated from the body- mainly feces and urine. Sewage: Liquid waste Sullage: Waste water excluding excreta; waste water from laundries, kitchens, bath rooms, etc which does not create bad smell. Night soil: Human excreta (Humans at times used to defecate at night in their backyard farms and used it to fertilize the soil/farm) Sewer: Pipe or conduit which is normally closed for carrying sewage. 123 6/8/2024 By Gadissa T.

124. Cont . . Effluent: Liquid waste that flows out. Influent: Liquid waste that flows in. Sewerage ( sewerage system): The organized network of drainage system used to remove or dispose sewage. Latrine: A pit or enclosure for urination or defecation (comfort room/toilet/ loo). Closet (water closet or W.C): The bowel used for excreta and urine in water closet (water flush) system. 6/8/2024 By Gadissa T. 124

125. Relationship of excreta to health and hygiene: Sanitation is defined as the safe management of human excreta and other waste products produced by the day to day activities of people. This definition includes the hard-ware and soft-ware (awareness) components, as effective interventions need to stimulate both the constructions of sanitary facilities for waste management and their hygienic use. Fecal-oral diseases are among the most common endemic disease throughout the developing countries and more so in Ethiopia. 125 6/8/2024 By Gadissa T.

126. Fecal- borne diseases and transmission: Understanding the six factors of the mechanism of disease transmission is vital for the control and breaking of the chain of transmission of excreta borne diseases. More so knowledge of the agent- host- environment dynamic interaction is also vital. In excreta borne disease transmission the significance of the 5Fs ( Feces, fingers, flies, fields /fomites and fluids ) should also be clearly known. 126 6/8/2024 By Gadissa T.

127. Figure: How diseases spread from excreta to a healthy person and the weakest links to break the chain of transmission through sanitation and hygiene. Hand washing Fingers Files Fields Food Death Excreta (feces) from sick person Debility New host Fluids Sanitary Latrine (sanitary barrier) Protection of water sources 127 6/8/2024 By Gadissa T.

128. Economic impacts of excreta borne diseases: Direct effect by the excreta borne disease organisms on the health of the individuals and the public through overt morbidity and mortality. Indirect effects : Promote other diseases (predispose to other diseases). Introduce /aggravate malnutrition Retard growth of children Retard intellectual development of children. Economic aspects Loss of working time (decrease productivity) Loss of skill (e.g. absenteeism from school and learning) High cost of treatment. Exposes to adverse effects of drug treatment 128 6/8/2024 By Gadissa T.

129. Effect of excreta borne diseases to public health in Ethiopia: Various studies made in the country and reports from health institutions indicate human excreta borne diseases are the most prevalent and dominant. Annual morbidity reports of the Ministry of Health (MOH) of Ethiopia for several years show 30-40% of all reported causes of morbidity are excreta For example , a report for a given year by the MOH on communicable diseases showed the following: Helminthiasis 30.6 % Dysentery (all forms) 20.3 % Bilhariziasis 0.5 % N.B. The sum for these three accounts to 51.4%. borne. 129 6/8/2024 By Gadissa T.

130. Factors influencing excreta disposal design and construction in a community The following factors influence design and construction of excreta disposal systems. Engineering factors of design construction, and installation: Selection of a system applicable to the specific community (culture, acceptance, design, reliability, durability, cost, location, etc ). Factors of construction include: Nature of ground formation Height of ground water table Types of local materials available for construction, etc. 6/8/2024 By Gadissa T. 130

131. Human factors: This includes the behavior, social and psychological factors such as the following: People may not use a given system which: They dislike Does not afford adequate privacy Can not be kept clean Is against their tradition and culture. Cost Factors: This is related to economical aspects. An excreta disposal system recommended to a community should be: Simple to construct, use, and maintain. Economical to build, maintain and replace. Can be constructed by local materials. 131 6/8/2024 By Gadissa T.

132. Biological and geographical factors: There are physical, chemical and biological factors that affect decomposition of excreta. These include: Temperature (heat or cold) Moisture content The above two are geographic factors which will be influenced by the latitude, altitude, and climate and soil formation. Organisms that help in breaking down the waste through the action of decomposition. Chemicals which may destroy the microorganisms helpful for decomposition. 132 6/8/2024 By Gadissa T.

133. Objective of human waste disposal system: The cardinal objective of human waste disposal system is to isolate totally human excreta from man’s food, water and the immediate environment at large. 133 6/8/2024 By Gadissa T.

134. The seven requirements (criteria) for selection of sanitary excreta disposal systems A sanitary excreta disposal system has to comply/fulfill the following seven criteria: Should not contaminate surface soil . Should not contaminate surface water . Should not contaminate ground water . The bottom of a pit latrine should be at least 1.5 meters above a ground water table. Should not be accessible to flies , roaches or other animals. Should be free of odor and unsightly conditions. There should be no handling of fresh excreta (In order to fulfill this criterion toilets have to be provided with a hand washing facility. The methods used should be simple, inexpensive to construct and operate. 134 6/8/2024 By Gadissa T.

135. Insects breeding in excreta: Common house flies, and green bottle flies can breed on excreta if it is not properly isolated from their reach. Cockroaches also frequently visit toilet facilities for food and hide outs which make them potential mechanical carriers for excreta borne diseases. Prevention of fly breeding in latrines depends on design and construction of the system (pit). Fly traps can be used in latrines; but they don’t seem successful. Disinfectants are not useful to control flies in latrines. Use of certain organic chemicals such as DDT, Aldrin leads to resistance. 135 6/8/2024 By Gadissa T.

136. 136 6/8/2024 By Gadissa T.

137. Excreta disposal methods/technologies: Excreta disposal methods are mainly two types: Non-water carriage and water carriage systems. 1. Non-water carriage systems : which normally do not use water for carrying away (transport) excreta. These are also called drop and store systems . Examples are: Pit latrine Ventilated Improved pit latrine (VIPL) Compost latrine Aqua privy Bucket latrine Trench latrine Overhung latrine Borehole latrine Ecologic Economic Sanitary Latrine (ECOSAN latrine). 137 6/8/2024 By Gadissa T.

138. 2. Water carriage systems: Excreta is deposited to properly constructed sanitary fittings and then carried away by water through a sewer system (a network of piping called drains and sewers) to its final disposal site. Water is the primary transporter of excreta in this process , hence it becomes contaminated. As the name indicates, a large quantity of water under pressure is used to remove the excreta from dwellings. The most preferred sanitary latrine is a water carriage system but is expensive and requires constant supply of water and a flushing system 138 6/8/2024 By Gadissa T.

139. The water carriage systems again can be grouped into three categories as follows: Drop - flush and discharge systems e.g. - Pour- flush latrine Individual containment and treatment systems e.g - Septic tanks - Cesspools - Soak/ Seepage pits Community treatment systems e.g - Municipal sewage treatment systems that may involve primary, secondary and tertiary treatment of sewage (Mechanical, biological and chemical treatments). 139 6/8/2024 By Gadissa T.

140. Typical examples of excreta disposal systems 1. The pit latrine/pit privy: Common in many parts of the world including rural areas of developed countries. It is a drop-and-store technology.   140 6/8/2024 By Gadissa T.

141. Dimension depends on: Family size (users) Number of holes to have Soil formation Ground water pollution Type of service expected (private communal or public). Its depth could be any size; but it should be at least 1.5 meters above ground water table. 141 6/8/2024 By Gadissa T.

142. Advantages of pit latrine: Low cost Easy to construct Uses all types of anal cleansing Minimum water requirement Fulfils most of the sanitary criteria if properly designed, constructed, used and maintained. 142 6/8/2024 By Gadissa T.

143. Disadvantages of pit latrine: Fly and mosquito nuisance Smell problem Lack of space for relocating new one when full Potential for ground water pollution Difficulty of construction in rocky formations. 143 6/8/2024 By Gadissa T.

144. Sitting a pit latrine: Location of a pit latrine depends on several factors. For greater convenience it should be located near the home, but not less than 10 meters from the home and kitchen to minimize odor, nuisance and fly problems to both. However, it should not be too far also as its likely-hood of using it regularly may be reduced. The pit should be located downhill below level of any well or water sources. In any way the latrine should be located not less than 15 meters (even in compacted soil formations) away from a water source. More-over, it should be located lee ward side from the home so wind blows not towards the home. 144 6/8/2024 By Gadissa T.

145. 2. The ventilated improved pit latrine (VIPL) : VIP Latrine is a technical modification of simple pit latrine. It is a drop-and-store technology. The difference from the traditional pit latrine is that it is modified to remove odor based on principles of air density and wind movement as well it is modified to prevent escape of flies that may enter or breed in the pit. Odor is removed through a vent pipe built on the slab and extended over the roof to about 50cm. 145 6/8/2024 By Gadissa T.

146. The top of the vent is screened so that flies coming out through the vent are trapped and unable to escape and finally drop back to the pit when they die. The higher density cooler air entering the pit through the hole displaces the pit gases to move through the vent pipe. Similarly the air current through the pit hole pushes the flies to go along the lighter pit gases through the vent pipe. Moreover, the super structure of the VIPL is made in such away the room is kept darker and flies through their photopositive characteristic are attracted to fly towards the light source through the top of the vent pipe. 146 Cont . . 6/8/2024 By Gadissa T.

147. As a result of the vent technology added VIPL improves the advantage of the pit latrine by: Eliminating fly breeding problem, Reduction of odor and nuisance. But to control flies and reduce odor, it is important the latrine fulfills the following: The vent pipe should be fitted with fly proof net. The inside of the superstructure should be kept dark. The door faces towards the prevailing wind and always kept closed to keep the inside dark. The pit hole is not covered to allow entry of heavy air draft. 147 Cont . . 6/8/2024 By Gadissa T.

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149. 149 6/8/2024 By Gadissa T.

150. Advantages of a VIPL: Bad odor is not felt provided the pit floor is kept clean. Flies get trapped by the screen on the vent pipe. Requires small space for construction. Fulfills the sanitary criteria if properly designed, constructed, used and maintained. Disadvantages of VIPL: Requires vent pipe Requires a concrete slab higher cost than ordinary pit latrine. May require lining or construction of a ring to prevent caving in. =======================///===================== 150 6/8/2024 By Gadissa T.

151. Food Hygiene (Food Safety) 151 6/8/2024 By Gadissa T.

152. Introduction Food is a nutritive substance taken into an organism for growth, or repair and for maintaining the vital processes. The major sources of foods are plants and animals. Food in order to meet expectations of a consumer has to fulfill the following aspects: Balanced palatable, attractive, culturally acceptable psychologically acceptable and Should not bear hazardous substances (MOs or chemicals that affect the health and wellbeing of the consumer and which may lead to spoilage of the food 152 6/8/2024 By Gadissa T.

153. Cont . . Most foods have to undergo some form of processing to preserve quality. In the process of growing, harvesting, storage and other processing the food may be exposed to chemical and bacteriological contamination. Food safety is now considered an integral part of nutrition. Microorganisms use our food for growth and multiplication utilizing the nutrients found in it & the consequences are: 1. Increasing their number 2. Changing the food flavor 3. Synthesis of new compounds Thus these phenomena may lead to food spoilage. MOs by accomplishing their task in nature (geochemical cycling of organic matter through decomposition) render our food unfit for consumption. 153 6/8/2024 By Gadissa T.

154. However, there are also MOs which have beneficial effects in food processing-such as in preparation of cheese. To prevent the undesirable effects of microorganisms on food we try: To prevent contamination To eliminate microorganisms (remove or destroy them) or 3. To prevent their growth. These are the three cardinal principles in food hygiene and safety to prevent the undesirable effects of microorganisms in food. 154 6/8/2024 By Gadissa T.

155. Definition of Terms FOOD : includes all substances whether in their natural state or in a manufactured or prepared form (any raw, cooked, or processed edible substance or beverage), which are part of the human diet. FOOD SAFETY/HYGIENE : means all measures necessary for ensuring the safety, wholesomeness, and soundness of food at all stages from its production until its final consumption and includes the proper disposal of garbage (food waste). ADULTRATED FOOD : if food contains any substance other than its genuine components or if it is not in its natural state or condition customarily it is known to be (food stuffs which may contain pathogenic agents; toxic agents , or chemicals; additive (except legally authorized); pesticides, insecticides or antibiotics; dirt, filth, insects etc ; food that is decomposed or fermented (unless intentionally done) is considered as adulterated. 155 6/8/2024 By Gadissa T.

156. MISBRAND : is the presence of any label, writing or printed matter which is false or misleading to the user or which violets any applicable governmental labeling requirements. In food hygiene misbranding, falsification of contents or conditions are usually described as adulteration practices. PERISHABLE FOOD : is any food of such a type or in such a condition which spoils easily unless proper preservation is exercised. e.g. vegetables, meat, fish, milk. STABLE FOODS : are foods that are not easily spoiled e.g. dry beans. POTENTIALLY HAZARDOUS FOOD : any perishable food which consists in whole or in part: milk and milk products, egg, meat, poultry, fish or other ingredients capable of supporting rapid and progressive growth of pathogenic organisms. Safe temperature: Is the range of temperature in which potentially hazardous foods are safely stored without spoilage. The recommended temperatures for storing potentially hazardous foods are 10 C or below or 60 C or above. 156 6/8/2024 By Gadissa T.

157. 60 140 157 10 50 6/8/2024 By Gadissa T.

158. Objective of Food Safety (Hygiene/ Sanitation) and Inspection To ensure that the food is safe and wholesome thus protecting the consumer/public from food-borne diseases. To prevent the sale of food which is offensive or defective in value or quality and to protect food from adulterants. To prevent spoilage due to microbial or chemical deterioration and wastage of food. To maintain aesthetic quality. 158 6/8/2024 By Gadissa T.

159. Causes of Food Spoilage The agents of food spoilage can be of internal or external sources. In general the causes can be: Microbial: bacterial, viral or protozoal Fungal: molds and yeasts Parasites (worms) Insects Simple physical or chemical changes such as dehydration, heating or freezing or reaction with surrounding air: oxidation etc.  Enzymatic or autolytic agents (chemical change that takes place within the food itself through the action of enzymes). Of the above listed spoilage agents; microbial and enzymatic agents are the commonest causes of spoilage 159 6/8/2024 By Gadissa T.

160. Food borne illnesses Food borne illness/disease is a general term applied to any disease which results from ingestion of contaminated foodstuffs. Food borne diseases are usually classified on the basis of the etiologic agent that causes a specific food born disease. In comprehensive terms, food borne diseases are divided into two broad categories, food poisonings/ intoxications and food infections. Each of them is further subdivided on the basis of etiologic agents 160 6/8/2024 By Gadissa T.

161. Food poisonings /intoxications generally result from toxins which are poisons ingested with contaminated foods. The source can be: Bacterial toxins Mycotoxins/ Fungal toxins Chemical poisons such as heavy metals like lead and mercury, insecticides etc. Certain toxic plant-tissues Toxic animal-tissues. Food infections include food borne diseases whose etiologic agents are microorganisms ingested with foods i.e. the organisms themselves are responsible for the diseases and not the toxins produced by them. 161 6/8/2024 By Gadissa T.

162. Food borne Diseases Food Poisonings Food infections Chemical poisonings Intoxications Caused by various pathogenic microorganisms ingested with foods Microbial intoxications Poisonous animal tissues Poisonous plant tissues Classification of food borne diseases. 162 6/8/2024 By Gadissa T.

163. Examples of Food borne Diseases: A. Food poisoning/ intoxication 1. Botulism Botulism is a disease caused by ingesting food which contains a preformed toxin produced by the organisms of clostridium botulinum . Botulinum is a saprophyte bacteria normally found in the soil; also found in plant crops, intestinal contents of animals; animal droppings, etc. It is a spore-former and is anaerobic . The spores are highly resistant to heat and other unfavorable environmental factors. When spores of C. botulinum enter foodstuff under favorable conditions, they germinate, multiply and form toxins in the food. 163 6/8/2024 By Gadissa T.

164. Conditions which are favorable for the formation of the toxin are: PH concentration of not below 4.5, also favorable moisture and temperature. The food must be hermetically sealed in order to create anaerobic condition in the container. There must be adequate time for the spores to germinate and produce sufficient toxin in the food before the food is ingested O utbreaks of botulism are commonly associated with home-canned or preserved foods, where the time-temperature factor is not carefully observed during processing of the foods. 164 6/8/2024 By Gadissa T.

165. Characteristics of the disease: Humans are susceptible to botulism if adequate dose of toxin is present in the food consumed. Typical symptoms appear 12-36 hours after ingestion of poisoned food (Incubation) The symptoms include: Earliest - acute digestive disturbances followed by nausea, vomiting and diarrhea Later - constipation, headache, fatigue, dizziness, double vision, and muscle paralysis Mortality rate is normally high and death occurs within short period. 165 6/8/2024 By Gadissa T.

166. General control measures: Prevent access of C. botulinum spores to foods. Destruction of spores or inhibition of their germination, by heat or other physical or chemical agents ( eg . PH > 5) Inhibition of bacterial growth and toxin production by refrigeration (- 5  C) Destruction of preformed toxin by heat . 2. Other examples of food poisoning/ intoxication include: Staphylococcal food poisoning. Food poisoning due to consumption of certain animal or plant tissues like shellfish poisoning, fungal poisoning (mushroom poisoning , mycotoxicosis, ergotism) and Chemical Food Poisonings (heavy metals like mercury, lead, pesticides and herbicides, radioactive agents…). 166 6/8/2024 By Gadissa T.

167. B.Food Infections   1. Salmonella food infection (Salmonellosis) Salmonellosis is a food infection due to ingestion of salmonella organisms with contaminated food, water or beverages. The genus salmonella belongs to the family known as Enterobactericeae in which most intestinal pathogens are classified. Genus salmonella has many species and subspecies. Salmonella are non-spore-forming, aerobic, Gram-negative bacilli . They are widely distributed in nature and grow and multiply in a wide range of nutritional, moisture, PH and temperature media. Almost all members of the genus salmonella are pathogenic for human animals or both. However, salmonella typhi organisms infect only humans. 167 6/8/2024 By Gadissa T.

168. Cont . . Incubation period after ingesting the organisms range from 6 to 72 hours, usually about 12 to 36 hours. The most frequent symptoms include: sudden onset of abdominal pain, diarrhea, headache, nausea and vomiting. Food stuffs commonly incriminated with Salmonellosis are meat and meat products, poultry, eggs, milk products and other various foods contaminated from human or animal origin, by feces and urine of mice and rats, and different domestic and wild animal sources including flies and cockroaches. 168 6/8/2024 By Gadissa T.

169. Prevention and control of Salmonellosis is rather difficult for several reasons, the main ones being: Salmonellae are widely distributed in nature in all types of climate & harbored in human & many various animal species. Compared to other gram-negative organisms they are relatively more resistant to different environmental factors. They grow in a wide temperature range (8  C to 45 C, optimum around 37 C). Grow at pH 4 to 8 Can tolerate well low moisture content Are resistant to drying, hence may survive in dried feces, animal droppings, dust, and soil for prolonged period of time. 169 6/8/2024 By Gadissa T.

170. Principles of control strategies of salmonellas: (Remember the 3 cardinal principles to prevent the undesirable effects of Mos ) Avoiding contamination of foods and beverages by salmonellae, be it from human, animal, soil, water etc sources. Inhibition of growth and multiplication of salmonellae in foods and beverages by creating unfavorable environmental conditions. Destruction of the organisms by such measures as proper cooking, boiling, pasteurization, etc 170 6/8/2024 By Gadissa T.

171. 2. Other examples of food-borne infections include: Shigellosis Amoebiasis Cholera E.coli 0157:H7 Parasitic diseases (tapeworms, trichinosis etc.) 171 6/8/2024 By Gadissa T.

172. Fig - Channels of Transmission of Feaco -oral Route Infections Via Food and Drinks Soil (Dust ) Animals Water Finger Food, Milk, Beverages, Vegetables Mouth of healthy person Source of infections. Human excreta (from patients & carrier s) Desability Death Insects (Flies) A sanitary barrier (latrine) 172 6/8/2024 By Gadissa T.

173. Food Sources And Suppliers (Public Food Service Establishments)   In many urban centers, eating and drinking in public food service establishments, such as restaurants, clubs, dining places, cafeterias, snack bars, canteens, has become common practice in different parts of the world. From a public health perspective, the greatest concern arises from the fact that these establishments prepare, handle and serve large quantities of food and drink to large groups of people within a short period of time. Unless foods are prepared, handled and served in a clean environment under hygienic conditions, they will spread food-borne diseases and affect a large number of people. 173 6/8/2024 By Gadissa T.

174. Food Service Establishments Sources of food or beverage supplies are called Food and Drinking Establishments/ Food Catering establishments or Food Service Establishments.  Not only have food service establishments increased in size, number, and kind, but techniques in preparation and distribution have changed as evidenced by the trend toward industrial catering and centralized preparation. Food prepared in a single kitchen may serve large numbers of persons in plants, schools, air planes, trains, hospitals and other institutions. These changes, in turn have created conditions whereby food processing, distributions and service need critical examinations. 174 6/8/2024 By Gadissa T.

175. The following are some of the existing food and drinking establishments in Ethiopia. Hotels - Groceries -Bakeries Restaurants - Pensions - pastries Bars - Bucher shops - Milk shop - Tea houses - Nightclubs Tej houses - Ordinary shops, etc….. 175 6/8/2024 By Gadissa T.

176. What Food Suppliers Should Fulfill: The food should be obtained from approved sources . The food should be wholesome and not adulterated . The food should not be misbranded . Original food container should be properly identified and it should come from an approved dispenser. Potentially hazardous foods are stored below 50  F (10  C) or above 140  F (60  C). The food is protected from any source of contamination including insect infestation and toxic chemical contamination. 176 6/8/2024 By Gadissa T.

177. The need for food protection: Food protection is needed in order to meet the following food Safety/hygiene objectives: To prevent and control food borne diseases To prevent and control food spoilage To protect food from adulterants To control importation of food-related diseases into the country and to ensure fair practices in the food trade. 177 6/8/2024 By Gadissa T.

178. Food Protection Measures: Sanitary facilities and requirements of design and construction of public food and drinking service establishments: The premises (which include the location, layout, size, and building quality) should be approved by health authorities to ensure the health and sanitary aspects are fulfilled. The floors, in which food is prepared, stored and served and where food utensils and equipment are washed and sanitized shall be of such construction that they are impervious, smooth but not slippery and of material that is easily cleaned. 178 6/8/2024 By Gadissa T.

179. Cont . . They shall not have cracks or crevices, the corners curved or rounded and well drained and should be constructed of a material that withstand splashing and constant washing and cleaning. Walls are smooth, light colored and washable up to the level reached by the spray or splash during cooking, washing or cleaning activities. Ceilings have smooth surfaces that do not collect dust; are generally white or light colored to facilitate better light reflection. Doors and windows are made of durable material, preferably self closing, closely fitting and air inlets screened. 179 6/8/2024 By Gadissa T.

180. Cont . . Windows usually serve for ventilation and lighting, hence window areas should be at least 10% of the floor area and at least 50% of the windows should be open able. Proper ventilation is effected by means of spacing and installation of windows, inlets, or exhaust fans if the need arises. Proper and adequate lighting (natural or artificial) in food service establishments is essential to enable people to see around comfortably without straining the eye. Adequate and safe water supply from approved source is available which is easily accessible to all rooms in which food is prepared and served and utensils and food containers are washed. 180 6/8/2024 By Gadissa T.

181. Provision for proper and safe disposal of human waste excreta and sewage. Adequate, safe and conveniently located toilet facilities for employees and clients should be available. All food premises should provide adequate and conveniently located lavatories with hot and cold water and soap. Food equipment and dishes are of approved material smooth easily to wash and to inspect, non-corrosive and not rusting and preferably enameled or made of stainless steel. 181 6/8/2024 By Gadissa T.

182. Dish washing/ methods of food utensils washing: Food utensils can be washed by hand (manually) or by machine. Hand (manual) washing is the most common and widely used method in developing countries. The accepted method in manual dishwashing is what is known as the 3 compartment, sink or vat system. This consists of 3 compartments/ sinks in which washing, rinsing and sanitizing activities are carried out in 3 consecutive steps after the soiled dishes have been scarped thoroughly and pre-washed to remove food remains. 182 6/8/2024 By Gadissa T.

183. The 3 compartment manual dish washing system (preferred system) Wash with warm water (43 C to 49 C) containing a detergent/ soap Rinse with Warm water Sanitize with hot water (77) C) for 2 minutes or with a chlorine solution of 50-100ppm for 2 minutes 183 6/8/2024 By Gadissa T.

184. Cont . . The sanitized utensils must finally be stored in a clean and protected (covered) place. Cups should be put upside down. Unnecessary hand contacts should be reduced to a minimum and improper handling procedures avoided. Washed utensils should be allowed to air-dry. Wiping (cleaning) with cloths or towels should be prohibited as microbes may be transferred from one utensil to the other through these materials. The cleanliness of the wiping materials is also a point of consideration. 184 6/8/2024 By Gadissa T.

185. Another accepted method but not a preferred system of dish washing is a 2 compartment/ vat with a flowing tap water Wash with warm water at 43 C to 49  C Rinse and sanitize with hot water 77 C for 2 minutes 185 6/8/2024 By Gadissa T.

186. Hygiene of food service employees (food-handlers) and application of appropriate food handling practices: The ways food may get contaminated are several: Human Excreta and sewage  Food handlers Contaminated water Dirty utensils and food contact surfaces Pesticides and other chemicals Raw food from Polluted environment infected sources (soil, dust) Rodents Flies, pests and domestic animals Food 186 6/8/2024 By Gadissa T.

187. A high proportion of food borne disease outbreaks more often originate from food handlers. Nearly all ordinances and codes require that food handling personnel shall be free from communicable diseases, shall handle food in accepted hygienic manners, and shall practice meticulously the rules of personal hygiene. Requirements for food handlers: The following requirements are most commonly stipulated in ordinances and codes for food handlers: Ensure that no person while known or suspected to be suffering from or to be a carrier of a disease likely to be transmitted through food or while affected with infected wounds, skin infection, sores or with diarrhea, is permitted to work in any food handling area in any capacity. The food handler must be trained and then constantly practice to keep his or her hands clear at all times.   187 6/8/2024 By Gadissa T.

188. Unguarded cough or sneeze 188 6/8/2024 By Gadissa T.

189. Cont . . Hands must be washed properly before preparation and serving of food, after using toilet or after break of work for any reason. Clean hands must be kept away from the mouth, nose or other parts of the body which may contaminate the clean hands with MOs from body discharges. Bad personal habits of a food handler 189 6/8/2024 By Gadissa T.

190. Keep the hands clean always 190 6/8/2024 By Gadissa T.

191. 191 6/8/2024 By Gadissa T.

192. 192 6/8/2024 By Gadissa T.

193. Cont . . Food handlers must use clean handkerchiefs while sneezing, coughing or blowing the nose around food; but also should ensure to wash their hands with a lot of water and soap after such acts. Food handlers are required to wear while at work clean, washable, light-colored ( white ) outer garments. The head must be covered with white head cover or hair net to prevent hair and hair dirt (dandruff) from falling on or around food. Street clothing is prohibited in food premises as it is likely to be contaminated while outside the food premises. Similarly work cloths (garments) should not be taken out of the food premises. In summary, food handlers must be free from food related communicable diseases, must maintain a high degree of cleanliness and conform to hygienic food handling practices. 193 6/8/2024 By Gadissa T.

194. Clean, white working cloths for food handlers 194 6/8/2024 By Gadissa T.

195. The 10 Golden rules of WHO for safe food Choose foods processed for safety Cook foods thoroughly Eat cooked foods immediately Store cooked foods carefully Reheat cooked foods thoroughly Avoid contact between raw and cooked food Wash ands repeatedly Keep all kitchen surfaces meticulously clean Protect food from insects, rodents and animals Use safe water 195 6/8/2024 By Gadissa T.

196. Medical certificates to food handlers:  Public health officials in some countries require a regular medical examination of food handlers and possession of a medical certificate to the effect that they are free from communicable diseases. The certificates are usually valid for a period of 3 to 6 months or a year and after which the medical examinations should be repeated for renewal of the certificate. However, this practice is currently questioned for the following reasons: Medical examinations are very expensive and seldom include some laboratory investigations. On the other hand even if laboratory investigations are included, the results may not always detect all the pathogens, or the pathogens are not being excreted at all time or because the organisms are not uniformly dispersed in the specimen examined; hence false negative results. 196 6/8/2024 By Gadissa T.

197. Cont . . On the other hand, possessing a medical certificate may create a false sense of security on the part of the individual food handler, the management and the consumers, and may lead to a relaxation of more important sanitary control measures. A food handler may develop a disease after the medical examination and certification. Therefore, effort should better be devoted to improving food-handlers attitude, hygiene and sanitary practices by organizing trainings and to routine sanitary monitoring by the management and health inspectors. However, it should be noted that persons who come into contact with food in the course of their work should have a medical examination prior to their employment. Thereafter, a medical examination should be undertaken whenever clinical and epidemiological evidence indicate the need for it 197 6/8/2024 By Gadissa T.

198. Methods Of Food Preservation To prevent Spoilage: We have seen that the causes for food spoilage are from two major sources. These are:   Internal sources: enzymatic activities (undesirable autolytic activity) which take place in the food itself. External sources: access of microorganisms to food from the external environment - air, water, soil, insects, animals and human beings. Like other organisms bacteria require basic materials and favorable environmental conditions in order to live and reproduce. These requirements are: balanced nutrients oxygen adequate water (moisture) favorable temperature and PH 198 6/8/2024 By Gadissa T.

199. Cont . . The principles and methods of safe food processing and preservation are aimed at eliminating favorable or creating unfavorable conditions for bacterial existence. What food preservation methods do you know to reduce spoilage of food and to have a longer keeping quality? 199 6/8/2024 By Gadissa T.

200. The following are methods implemented in food preservation: 1. Dehydration: This is removing of water or a method of drying which is one of the oldest methods of food processing and preservation. Dehydration can be achieved by heat including sun drying or the use of certain chemicals like salt, sugar or smoking. This is done in order to reduce the moisture content and thus create an inadequate moisture level for bacterial growth and multiplication . 2. Pickling: This is a general term used when immersing certain food items in concentrated natural acid solution such as vinegar or similar chemicals for preservation. 200 6/8/2024 By Gadissa T.

201. 3. The use of high temperature: Heat is one of the oldest methods of destroying microorganisms in food processing and preservation. Sterilization, disinfection and pasteurization are common methods which make use of heat. For the destruction of MOs the time-temperature relationship ;Thermal Death Time (TDT) or Thermal Death Point (TDP) for given species should be taken into consideration. 201 6/8/2024 By Gadissa T.

202. 4. Canning: One of the most widely used modern preservation methods of food. The principles are: Sterilizing foods to be canned and Packing in sterile, air tight, stainless metal, glass or plastic containers; and hermetically sealing the containers to prevent contamination during handling and storage. . Use of low temperature Low temperature: Temperatures normally ranging from 10  C to 0  C (50  F to 32  F) or lower retard or arrest the metabolic process of most microorganisms. Low temperatures produce bacteriostasis and do not necessarily kill microbes in refrigerated foods. Freezing: preservation by freezing is achieved by using temperatures below 0  C (32  F). 202 6/8/2024 By Gadissa T.

203. Cont . . Freezing is a dehydration method in which the water content of foods is decreased by transforming it into ice, thus making water virtually unavailable for microbial metabolic processes. The freezing temperature will depend upon the kind of food and the intended storage time. . Use of pH: Most species of pathogenic and spoilage bacteria normally grow best at neutral pH level (pH7.0), or at slightly alkaline or slightly acid pH values. 7. Fermentation: Is essentially a process of transforming foods into an acid state, hence based on pH control techniques- e.g. sour milk (lactic acid production). 203 6/8/2024 By Gadissa T.

204. Control of vectors in food services: Provision for effective control measures against vermin is one of the important requirements for ensuring the safety of food for human consumption. Vermin: is defined as noxious, mischievous, or disgusting animals of small size of common occurrence, and difficult to control. In food hygiene the most dangerous vermins are the flies, cockroaches and the rats. I. The flies (these information also apply to cockroaches as well) Flies have been and still are the intimate associates of humanity since the dawn of recorded history. The common housefly is the most hazardous contaminant of food and transmitter of food borne diseases to people. Given the large number of eggs laid and the rapid rate of development, fly populations reach alarming proportions unless control measures are taken at an appropriate time. 204 6/8/2024 By Gadissa T.

205. Cont . . Houseflies can breed practically in any most decaying or fermenting human, animal and plant wastes including on excreta. Houseflies have been known to be the most dangerous contaminant of food; a mechanical transmitter of disease agents. The explanation for this trait lies in its anatomical structure, peculiar breeding and feeding habits, and its close companionship to human beings and their habitations. The following are diseases related to food borne where flies play a major role: Amoebic and bacillary dysentery, typhoid, cholera, Salmonellosis, poliomyelitis, infectious hepatitis, etc.   205 6/8/2024 By Gadissa T.

206. Control methods of common house flies: A thorough knowledge of the fly life cycle, characteristics, habits and awareness of its menace to human health is prerequisite for any fly control program. Based on this background, control measures can be devised as follows: A. The foundation for all successful fly control activities is the elimination of all actual and potential fly breeding places. i ) Proper disposal of excreta: Building and proper use of fly-proof latrines such as the VIP latrines Safe disposal of sewage Safe disposal of all animal wastes and other moist, rotting or decomposing organic matter from premises and neighborhoods. 206 6/8/2024 By Gadissa T.

207. Cont . . ii) Proper collection, storage and disposal of solid waste: Refuse, garbage etc. B . Making food and food contact surfaces inaccessible to flies: eg . by screening of doors, windows &other inlets. C.Reduction of fly populations by killing adults using such methods as fly trapping, fly paper, fly wire or strips. D. Destruction of flies by poisoning: As a general rule vigilance and continuous application of basic sanitation should be used as the only effective and lasting method of fly control. Therefore, control measures based on insecticide use (poisoning) should be considered with great caution since insecticides are considered as environmental pollutants; hence undesirable for routine use. 207 6/8/2024 By Gadissa T.

208. II. Rat control in food premises: The rat is often compared to humanity. Like human it adopts itself to all kinds of climates, eats almost all kinds of foods that humans eat and breeds at all seasons. In economic terms, it is one of the most destructive animals of human foods and properties. The public health aspects of the rat problems are that it eats, destroys, and contaminates foods destined for human consumption and is responsible for the spread of several important diseases to man via food and other means.   208 6/8/2024 By Gadissa T.

209. Cont . . A large number of infections may be contracted by people through food or water contaminated by excreta and urine of rates besides direct contact contaminations. Some of rat borne food infections include: Salmonellosis, trichinosis, leptospirosis, hepatitis A virus, etc. i . Environmental control: Rats require food, water and harborages for their existence and multiplication. Hence the fundamental principle of rat controlling lies on how successful we are in denying or eliminating these life support system in an area. Methods of environmental control include: Proper storage, collection and disposal of solid wastes, particularly garbage. Proper housekeeping and maintenance of sanitary conditions in food premises, household and the neighborhoods. Elimination of all actual and potential conditions which are likely to provide harborage and food. 209 6/8/2024 By Gadissa T.

210. ii. Rat proofing, stoppage or blocking: Rat proofing of buildings when planning and constructing, sealing off all openings of both outside and inner walls, roofs, doors, windows etc through which rats are likely to enter . iii. Killing the rats: Trapping using snap traps or cage traps. Poisoning: Rats can be killed by using rodenticides but done with great precautions. All poisons should be handled and applied only by knowledgeable persons with highest precautions to prevent danger of access to food, human, domestic animals or irresponsible persons. 210 6/8/2024 By Gadissa T.

211. GALATOOMAA! Thank you 6/8/2024 By Gadissa T. 211