There are a range of environmental health hazards that affect our wellbeing. Hazards can be grouped together to improve understanding and action planning. The actions that you need to carry out to protect the health of your community depend on knowing how these hazards can affect us all. In this study session, you will learn about the types and categories of environmental health hazards, the routes of exposure and the ways of preventing and controlling these hazards.
When you have studied this session, you should be able to:
2.1 Define and use correctly all of the key words printed in bold. (SAQ 2.1)
2.2 Describe the main categories of environmental health hazards. (SAQ 2.2)
2.3 Explain the principles of hazard management. (SAQ 2.3)
2.4 List and describe the main types of environmental pollution. (SAQ 2.4)
2.5 Explain the basic principles of pollution management. (SAQ 2.4)
In Study Session 1, you learned that environmental health addresses the assessment and control of environmental factors that can potentially affect health. It is targeted towards preventing disease, creating health-supporting environments and encouraging positive human behaviours. You have also learned about the general issues of environmental health risks. Our environment generally consists of physical, chemical and biological factors and our relationship with our environment is always interactive. This means that we affect our environment and our environment affects us. These interactions may expose us to environmental health hazards; that is any environmental factors or situations that can cause injury, disease or death.
It is worth pausing here to clarify the difference between hazard and risk. A hazard is something which is known to cause harm, that is, a source of danger to health. Risk is the likelihood or probability of the hazard occurring and the magnitude of the resulting effects. For example, if you climb a ladder you know there is a chance you could fall off and be injured, although it is unlikely. The ladder is the hazard and the chance of injury is the risk you take by climbing the ladder.
We will illustrate an environmental health hazard with an example. The production of cow dung cake to be used for fuel is a common practice in Ethiopia. Fresh dung supports the breeding of flies. Dung cake is usually prepared near to the house (Figure 2.1). Young flies need food and move from the dung to the food that is found in the house.
The flies pick up pathogenic organisms from the dung and transfer them to fresh food that is ready for consumption. A child eats the contaminated food and gets diarrhoea in a few days.
The conditions or the situation of producing dung cake close to the house is hazardous (or dangerous) because it facilitates the breeding of flies near to fresh food in the house. The infected food is the hazard that damages the child’s health. In this example, the hazard arises because of the infectious agent (the pathogenic organisms) and the process or condition (the preparation of cow dung cake close to the house). The risk of getting an infection is very high if someone consumes food that is contaminated with an infectious agent.
What causes environmental hazards? List some different types of natural and human-produced hazards.
You may have listed a number of factors. Natural hazards include earthquakes, volcanic eruptions and flooding. Human-produced hazards are mainly related to pollution of the air, water and soil, and contamination of food.
Hazards are generally categorised as follows:
Physical hazards are those substances or conditions that threaten our physical safety. Fires, explosive materials, temperature (hot or cold), noise, radiation, spills on floors and unguarded machines are some examples of physical hazards.
Physical hazards also include ergonomic hazards which occur when the type of work, body position and working conditions put strain on your body. This happens when your capacity for work is restricted by the type of work. These instances are hard to spot since you don’t always immediately notice the strain on your body or the harm these hazards cause. Short-term exposure in badly designed work may result in muscle fatigue or tiredness, but long-term exposure can result in serious long-term injuries of the musculo-skeletal system. Injera baking is one of the hardest tasks a woman faces routinely.
She spends one to two hours in a forced sitting and bending position which can be damaging to her body. Ergonomic hazards also exist among farmers, for example while manually ploughing and cleaning the weeds in farmland (Figure 2.2).
Biological hazards are organisms, or by-products from an organism, that are harmful or potentially harmful to human beings. They include pathogenic bacteria, viruses and parasites, and also toxins (poisons) that are produced by organisms. Biological hazards are the cause of the majority of human diseases. For example, bacteria cause cholera, tuberculosis, leprosy, relapsing fever and many diarrhoeal diseases; viruses are responsible for hepatitis B and C, HIV, measles and polio; and there are many diseases caused by parasites. A parasite is any organism that lives on or in another organism, called the host, and causes damage, ill health or even death to the host. Some human parasites are external and live on the skin and hair, for example, mites that cause scabies. Internal parasites, living inside the body, include protozoa and helminths.
Protozoan parasites are single-celled organisms that enter the body either by ingestion or via the bite of an infected insect. Malaria, sleeping sickness and leishmaniasis are examples of diseases caused by protozoan parasites introduced by insect bites; amoebic dysentery and giardiasis result from drinking or eating contaminated water or food.
Helminths are parasitic worms that live inside the body. Several helminths have complicated life cycles involving humans and other animals as secondary hosts. They have different routes of entry into the human body depending on the type of worm including ingestion with food or water, the faeco-oral route, insect bites and penetration through the skin. ‘Helminth’ is the general term used to describe several different types of parasitic worm. There are three main groups: tapeworms, roundworms and flukes. Tapeworms may be ingested with food, especially under-cooked meat, or with water or soil contaminated with faeces. Roundworms, also called nematodes, are responsible for many different diseases including ascariasis, dracunculiasis (guinea worm), filariasis, hookworm, onchocerciasis (river blindness), trichinosis and trichuriasis (whipworm). A type of fluke is the cause of schistosomiasis, also known as bilharzia. People become infected with schistosomiasis, not through food, but by standing or swimming in water that contains the immature form of the fluke; these are released into the water from the snail secondary host. The fluke gets into the water and the snail from the excreta of infected people.
Biological hazards arise from working with infected people or animals, or handling infectious waste and body fluids, as well as contact with unsafe water, food and waste. The hazards may occur in the home, at school or at work. In particular, work in hospitals, hotel and hospital laundries, laboratories, veterinary offices and nursing homes may expose someone to biological hazards.
Chemical hazards are present when a person is exposed to a harmful chemical at home or at work. The chemicals can be in the form of gases, solids or liquids. Exposure to chemicals could cause acute health effects (an immediate or rapid onset) if taken in large quantities in a single dose; and chronic health effects (long-term effects on health) if taken in small doses over an extended time. Detergents (powdered soap, bleaching powder), drugs (veterinary and human) and pesticides (DDT, malathion, diazinon, zinc phosphide, warfarin) are chemical hazards that are commonly found in rural households (Figure 2.3). Farmers, young children (under 5 years) and household animals are vulnerable to chemical exposure, but it is always possible that anyone might come into contact with the chemical during preparation, spraying, use or storage. A person is exposed to chemicals through various ways: through inhaling the vapours, gases or dusts; through skin contact with solvents, acids and alkalis; and through ingestion of unknown chemicals with food and water.
Incomplete burning of fuel releases carbon monoxide (CO) which is a chemical hazard. When breathed in, CO binds to the haemoglobin in our blood, reducing the uptake of oxygen; the cells of the body then suffer because they are not getting enough oxygen. This can result in severe sickness and even death.
Culture is the knowledge, belief, art, law, morals, customs and habits that are acquired by people as members of society. It is also the common ways of life and set of thoughts and feelings shared by the members of a society. Just as there are cultural practices that are good for health, such as breastfeeding a child, there are also cultural practices that adversely affect health and these can be considered to be cultural hazards. There are practices that are widely accepted and found in different areas of Ethiopia that can be hazards for health; for example, the belief that evil spirits are the source of diseases, practices of storing drinking water uncovered, open defecation and not handwashing before meals and after latrine use.
Hygiene and health promotion and community mobilisation are critical interventions that help improve practices that are not useful to the community. To change human behaviour away from undesired practices, you need to change knowledge and attitudes.
Let us assume you have observed that one of the households in your area has a clean latrine but it has not been used for the last few months. What could be the explanation for not using the latrine?
You may have thought of some different reasons, but here are some we have thought of:
Poverty and illiteracy are examples of social hazards. We know that poor and uneducated people get sick more frequently, compared to wealthier and more educated people. Alcoholism, obesity, smoking and drug abuse are also social hazards that affect our health. A person with such habits is, over time, degraded, not respected by society, physically and mentally dissatisfied, and ultimately is likely to suffer with chronic illnesses such as lung and cardio-vascular diseases.
To reduce the adverse impacts of environmental hazards on human health you need to understand where the hazard comes from, identify it and the pathway it can take to affect people.
The source of the hazard is the place of origin from proposed and existing activities. Patients and carriers discharge infectious agents (biological hazards) that could infect healthy people. Industrial processes in a factory release chemical hazards that may be found in sewage; the sewage could reach drinking water, thereby creating the possibility of ingesting these chemicals. Household activities could also be sources of hazards, for example, cooking with fuels such as animal dung and charcoal produces toxic smoke that can cause lung diseases.
The type of hazard is the particular chemical, infectious agent or other agent involved. The pathway is the route by which the hazard gets from the source to the person.
The response or the effect is the health outcome (changes in body function or health) after the hazard has affected the person. The amount and type of change (or response) depends on the type of hazard and the effect it can have on different people. This would depend on the person’s individual health and factors such as their age; for example, young children or people who are already sick are often more harmed by diseases such as diarrhoea than healthy adults.
If you want to prevent a hazard, you need to understand the source of the hazard (where it comes from), the type of hazard (for example the type and concentration of a chemical), the pathway (the affected environment and how the exposure could take place), and the response (the effect the hazard could have on people).
We will demonstrate this with an example. Sewage containing cadmium (a toxic chemical) is produced by a hide-processing factory and flows into a river. People downstream of the point of discharge drink the contaminated water and become sick. The hazard exposure is described as follows:
You may be asked to plan how to manage environmental hazards, say in a Health Post or mill house that exists in your locality. Involvement in hazard management requires you to follow certain steps, which are outlined below.
The process of hazard management is shown in Figure 2.4.
We have seen that hazards are things that endanger human health or life, but hazards can also be harmful to our environment. Pollution is the introduction of contaminants into an environment causing harm, instability or disorder to the ecosystem. (An ecosystem includes all the living organisms (plants, animals, microorganisms) and their physical environment and the interactions between them.) Pollution can be also defined as the presence of a substance in a medium or environment that results in a change to its ‘natural’ state, potentially causing an adverse effect. Pollution, however, is not simply the introduction of contaminants. There is always a response in the form of modification or change in the environment. From this standpoint, pollution is the harm that results because substances are present where they would not normally be found, or because they are present in larger than normal quantities.
Contaminants are not necessarily pollutants. A contaminant is a minor substance, material or agent that is unwanted in the environment and may or may not be harmful. A pollutant is a contaminant which, due to its properties or amount or concentration, causes harm. Gases (carbon monoxide, ozone, nitrogen dioxides), chemical vapours, dust particles, fumes and liquid chemicals (pesticides, solvents, drugs, acids, etc.) are examples of potential pollutants of air and water ecosystems.
In nature, the environment has an inherent capacity to clean itself through self-cleaning processes. Natural environmental processes have the ability to deal with many pollutants and correct most imbalances if given enough time. For example, self-cleaning processes in a river could involve:
You will learn more about these processes in Study Session 17.
Pollutants can come from natural or man-made sources. Examples of natural sources of pollution are volcanoes which give out ash and dust into the atmosphere and metals such as arsenic which are naturally present in some rocks and soils. Man-made pollutants can come from industrial, domestic (home), transport and agricultural sources.
Think of one example of a pollutant from industrial, domestic (home), transport and agricultural sources.
There are lots of different examples that you could think of. Here are some that we came up with:
Pollution can take many forms. The air we breathe, the water we drink, the soil where we grow our food, and even the increasing noise we hear every day all contribute to health problems and a lower quality of life. Pollution can be classified as:
This occurs with the release of chemicals in gaseous or dust form into the atmosphere. Household cooking, industries, vehicles and incinerators are common sources of air pollution.
Water can be polluted by the release of liquid waste (human, animal or industrial) into rivers, streams and lakes. A common type of water pollution is organic material such as human and animal wastes and in waste water from food processing. These wastes can be removed from rivers and lakes by the self-cleaning processes described above but, if present in large quantities, the biodegradation process can reduce the level of dissolved oxygen in the water so much that fish and other aquatic life cannot survive. As well as these environmental impacts, water contaminated with human waste is a significant cause of many diseases that will be described in more detail elsewhere in this Module. Some pollutants can be extremely harmful even if they are taken in small quantities and may cause cancer, reproductive health effects (abortion, embryo malformation, birth defects) or nerve damage when the contaminated water is consumed.
This occurs when land is used as a site for accumulating wastes that are generated from various sources (industry, agriculture, health facilities, villages, private and public organisations). These wastes may be biologically, chemically or physically hazardous to plants and animals. The pollution by chemicals such as pesticides may have long-term consequences, such as groundwater pollution.
Explain the differences between a hazard, a contaminant and a pollutant.
A hazard is anything that harms our health. A contaminant is something introduced to the environment (air and water) that may or may not pose a significant health risk. A pollutant is a contaminant introduced into the environment that adversely affects animal and human life.
There are two main approaches to pollution management:
There are a number of principles of pollution prevention; we will briefly discuss some of them.
Principle of waste optimisation: The motto in this principle is ‘Do not produce any waste; if this is not possible, reduce or minimise waste generation as much as possible’.
There are three ‘Rs’ that are applied in waste optimisation: Reduce, Reuse and Recover. Figure 2.6 shows the hierarchy or the order in which the waste optimisation options should be used. Reduction refers to changing the process so that waste is not produced in the first place. Reuse involves using an item more than once (for example you can reuse plastic bottles for collecting water). Recovery involves recovery of materials or energy through recycling, composting and incineration. An example of recycling is taking used aluminium cans (tin cans) and recycle the metal to make it into something else. In composting we can take waste organic matter and make it into useful compost for fertiliser. Through incineration (burning) we can recover the energy contained in waste materials. There is more information on these processes in Study Session 22 on solid waste management.
The concept of waste optimisation is applied in industries through cleaner production. Cleaner production implies appropriate environmental management, waste minimisation, replacement of toxic chemicals, process and product modification, and the application of the three ‘Rs’.
Polluter pays principle: This principle identifies the people or organisations who generate or produce waste or pollution as those who are accountable for any human or ecological damage. They are responsible for paying the costs of any damage. The principle is an economic tool to enforce accountability and responsibility. Strict standards for pollutant discharge permissions and enforcing heavy taxation on products or waste handling are ways of making the polluter pay.
Principle of ‘Cradle to Grave’: This principle applies to the production of any object or to any activity by an individual or institution and all the pollution that object or activity might cause throughout its lifecycle; that is, from its ‘cradle’ to its ‘grave’. For example, if you make a plastic bottle, pollution might be caused in the manufacturing process; pollution is also caused by the lorries that transport the bottles around the country; and pollution is caused when the bottle is thrown away. All these aspects should be taken into account.
Precautionary principle: For any activity, there is an obligation not to cause harm even when someone is uncertain about the effect of the activity on humans and the environment. Under this principle, you take precautions to avoid environmental damage, even if you are not certain that damage will result. The application of waste minimisation is an example.
Principle of duty of care: Any person or organisation that produces waste, i.e. a waste generator, has a citizenship and ethical obligation to handle their waste properly. They have a duty to ensure that it does not harm other people or the environment.
Principle of discharge/emission permit: A waste generator has an obligation to obtain permission from the regulatory authority in order to discharge waste to surface water and to the atmosphere.
Principle of sustainable development:
What do you remember about the term ‘sustainable development’?
Sustainable development is ‘development which meets the needs of the present without compromising the ability of future generations to meet their own needs’. You could think of this as friendly coexistence where people and the environment sustain each other.
Sustainable development requires people to carry out environmental mitigation (lessening the damaging effects) for newly developed factories, dams, irrigation schemes and other undertakings as prescribed by law.
Principle of the right to know: The public has the right to information about pollution from a particular process. Public participation at various stages of project development avoids mistrust and the consequences of conflicts of interest.
Pollution prevention through various applicable principles and methods is not always possible and the consequence is that some pollution is produced. If pollution is produced, there should be some measures to control it and minimise the effects on people and the environment. The application of waste treatment before disposal, restricting contact between the waste and the public, and monitoring and evaluating the effect of the waste on the immediate environment are some of the intervention options in waste control. Pollution control options will be explored later in this Module.
In Study Session 2, you have learned that:
Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions. Write your answers in your Study Diary and discuss them with your Tutor at the next Study Support Meeting. You can check your answers with the Notes on the Self-Assessment Questions at the end of this Module.
Match the descriptions with the following key terms: hazard and pollution, contamination. Explain the reasons for your answer.
Using the following two lists, match each numbered item with the correct letter.
A mill house is releasing its liquid waste into a nearby river. The community drinks the water below the discharge point. There was no complaint when people drank the water. There were no observations of fish dying. The amount of the chemical was not significant.
Later a new industry releases its liquid waste into the same river. The mill house also continued to release its waste. Fishes in the river began to die. Fishing became difficult. The community downstream did not like the taste of the water.
The amount of the chemical was not known. No one knows if the chemical in the waste is harmful or not.
The first description is identified as contamination because there is no evidence of harm. This is in contrast with the second in which the wastewater causes death of fish and makes the water taste bad; therefore this is pollution. The appropriate term for the third description is hazard because we have little information about the agent involved or the probability of it causing harm, but we can say there is a danger.
Have a walk-through visit at the Health Post in your locality and think about any environmental hazards you might find there. List the types and sources of possible hazards and their health effects.
You may have identified a range of hazards; here are some possibilities.
|Type of hazard||Source of hazard||Possible health effect|
|Biological hazard: pathogenic microorganisms (bacteria, fungi, protozoa, worms)||Infected discharges (e.g. blood, secretions, oral swabs, pus)||Communicable diseases such as TB, diarrhoea typhoid fever|
|Physical hazard: slips and trips||Wet or slippery floor||Broken bones, muscle injuries, twists and sprains|
|Chemical hazard: drugs, detergents||Medicines and cleaning products used and stored in the Health Post||Poisoning, skin or lung damage|
Describe the key steps in hazard management planning. Using your answer to SAQ 2.2, what are the appropriate interventions for the hazards you have identified?
The first step in hazard management planning is to identify the hazard including its type, source and the route of exposure. Then the potential to cause harm must be evaluated (risk analysis). When the hazard and risk have been assessed, this information must be shared with other people involved. Possible interventions to reduce the risk or measures to control or remove the hazard should be decided and then put into effect. The outcomes from the interventions or control measures must be monitored to check if they have been successful. Throughout this process, detailed records must be kept of the hazards and actions taken to control them.
Your list of appropriate interventions will depend on your own answer to SAQ 2.2. This is a response for the answer we provided.
|Type of hazard||Source of hazard||Intervention|
|Biological hazards: pathogenic microorganisms (bacteria, fungi, protozoa, worms)||Infective discharges (blood, secretions, oral swabs, pus)||Personal hygiene (handwashing, hand disinfection); proper disposal of wastes; disinfection and sterilisation of medical equipment|
|Physical hazard: slips and trips||Wet or slippery floor||Ensure floors are cleaned properly; mop up spills; warn people of slippery floors|
|Chemical hazard: drugs, detergents||Medicines and cleaning products used and stored in the Health Post||Store detergents properly in labelled containers; use according to instructions; use protective equipment such as gloves|
Think about the possible types of pollution that could be produced from a health centre.
a.The types of pollution from a health centre could be air, water and land pollution. Water pollution may occur if sterilising fluids are discharged into a nearby river. Air pollution may arise from the burning of wastes. Land pollution is possible if health centre wastes are not disposed of correctly.
b.There are two main approaches to pollution management: pollution prevention (which should be used to stop pollution being produced in the first place or reducing any waste generation at the source where possible) and pollution control (the measures taken to control pollution and wastes after they have been generated or produced).