STUDY UNIT
LEARNING OBJECTIVES
After having worked through this study unit, students are expected to:
5.0 HAZARD IDENTIFICATION AND CLASSIFICATION
5.1 Hazard classification
The contact of man with objects and conditions in his working environment can produce harmful and injurious effects to health. These factors in the environment are called hazards and can be classified in six categories as follows:
(hazard classification pg 36-39)
Recognition of hazards
A workplace hazards can be defined as any condition that may adversely affect the well-being or health of exposed persons. Recognition of hazards in any occupational activity involves characterization of the workplace by identifying hazardous agents and groups of workers potentially exposed to these hazards. The hazards might be of chemical, biological or physical origin (see table 30.1). Some hazards the work environment are easy to recognize-for example, irritants, which have an immediate irritating effect after skin exposure or inhalation. Others are not so easy to recognize-for example, chemicals which are accidentally formed and have no warning properties. Some agents like metals (e.g., lead, mercury, cadmium, manganese), which may cause injury after several years of exposure, might be easy to identify if you are aware of the risk. A toxic agent may not constitute a hazard at low concentrations or if no one is exposed. Basic to the recognition of hazards are identification of possible agents at the workplace, knowledge about health risks of these agents and awareness of possible exposure situations.
Table: Hazards of chemical, biological and physical agents
Type of hazard |
Description |
Examples |
CHEMICAL |
Chemicals enter the body principally through inhalation, skin absorption or ingestion. The toxic effect might be acute, chronic or both., |
|
Corrosion |
Corrosive chemicals actually cause tissue destruction at the site of contact. Skin, eyes and digestive system are the most commonly affected parts of the body. |
Concentrated acids and alkalis, phosphorus |
Irritation |
Irritants cause inflammation of tissues where they are deposited. Skin irritants may cause reactions like eczema or dermatitis. Severe respiratory irritants might cause shortness of breath, inflammatory responses and oedema. |
Skin: acids, alkalis, solvents, oils Respiratory: aldehydes, alkaline dusts, ammonia, nitrogendioxide, phosgene, chlorine, bromine, ozone |
Allergic reactions |
Chemical allergens or sensitizers can cause skin or respiratory allergic reactions. |
Skin: colophony (rosin), formaldehyde, metals like chromium or nickel, some organic dyes, epoxy hardeners, turpentine |
Asphyxiation |
Asphyxiants exert their effects by interfering with the oxygenation of the tissues. Simple asphyxiants are inert gases that dilute the available atmospheric oxygen below the level required to support life. Oxygen-deficient atmospheres may occur in tanks, holds of ships, silos or mines. Oxygen concentration in air should never be below 19.5% by volume. Chemical asphyxiants prevent oxygen transport and the normal oxygenation of blood or prevent normal oxygenation of tissues. |
Simple asphyxiants: methane, ethane, hydrogen, helium |
Cancer |
Known human carcinogens are chemicals that have been clearly demonstrated to cause cancer in humans. Probable human carcinogens are chemicals that have been clearly demonstrated to cause cancer in animals or the evidence is not definite in humans. Soot and coal tars were the first chemicals suspected to cause cancer. |
Known: benzene (leukaemia); vinyl chloride (liver angio-sarcoma); 2-naphthylamine, benzidine (bladder cancer); asbestos (lung cancer, mesothelioma); hardwood dust (nasalor nasal sinus adenocarcinoma) Probable: formaldehyde, carbon tetrachloride, dichromates, beryllium |
Reproductive |
Reproductive toxicants interfere with reproductive or sexual functioning of an individual. |
Manganese, carbon disulphide, monomethyl and ethyl ethers of ethylene glycol, mercury |
|
Developmental toxicants are agents that may cause an adverse effect in offspring of exposed persons; for example, birth defects. Embryotoxic or foetotoxic chemicals can cause spontaneous abortions or miscarriages. |
Organic mercury compounds, carbon monoxide, lead, thalidomide, solvents |
Systemic |
Systemic poisons are agents that cause injury to particular organs or body systems. |
Brain: solvents, lead, mercury, manganese |
BIOLOGICAL |
Biological hazards can be defined as organic dusts originating from different sources of biological origin such as virus, bacteria, fungi, proteins from animals or substances from plants such as degradation products of natural fibres. The aetiological agent might be derived from a viable organism or from contaminants or constitute a specific component in the dust. Biological hazards are grouped into infectious and non-infectious agents. Non-infectious hazards can be further divided into viable organisms, biogenic toxins and biogenic allergens. |
|
Infectious hazards |
Occupational diseases from infectious agents are relatively uncommon. Workers at risk include employees at hospitals, laboratory workers, farmers, slaughterhouse workers, veterinarians, zoo keepers and cooks. Susceptibility is very variable (e.g., persons treated with immunodepressing drugs will have a high sensitivity). |
Hepatitis B, tuberculosis, anthrax, brucella, tetanus, chlamydia psittaci, salmonella |
Viable organisms and biogenic toxins |
Viable organisms include fungi, spores and mycotoxins; biogenic toxins include endotoxins, aflatoxin and bacteria. The products of bacterial and fungal metabolism are complex and numerous and affected by temperature, humidity and kind of substrate on which they grow. Chemically they might consist of proteins, lipoproteins or mucopolysaccharides. Examples are Gram positive and Gram negative bacteria and moulds. Workers at risk include cotton mill workers, hemp and flax workers, sewage and sludge treatment workers, grain silo workers. |
Byssinosis, “grain fever”, Legionnaire's disease |
Biogenic allergens |
Biogenic allergens include fungi, animal-derived proteins, terpenes, storage mites and enzymes. A considerable part of the biogenic allergens in agriculture comes from proteins from animal skin, hair from furs and protein from the faecal material and urine. Allergens might be found in many industrial environments, such as fermentation processes, drug production, bakeries, paper production, wood processing (saw mills, production, manufacturing) as well as in bio-technology (enzyme and vaccine production, tissue culture) and spice production. In sensitized persons, exposure to the allergic agents may induce allergic symptoms such as allergic rhinitis, conjunctivitis or asthma. Allergic alveolitis is characterized by acute respiratory symptoms like cough, chills, fever, headache and pain in the muscles, which might lead to chronic lung fibrosis. |
Occupational asthma: wool, furs, wheat grain, flour, red cedar, garlic powder |
PHYSICAL HAZARDS |
|
|
Noise |
Noise is considered as any unwanted sound that may adversely affect the health and well-being of individuals or populations. Aspects of noise hazards include total energy of the sound, frequency distribution, duration of exposure and impulsive noise. Hearing acuity is generally affected first with a loss or dip at 4000 Hz followed by losses in the frequency range from 2000 to 6000 Hz. Noise might result in acute effects like communication problems, decreased concentration, sleepiness and as a consequence interference with job performance. Exposure to high levels of noise (usually above 85 dBA) or impulsive noise (about 140 dBC) over a significant period of time may cause both temporary and chronic hearing loss. Permanent hearing loss is the most common occupational disease in compensation claims. |
Foundries, woodworking, textile mills, metalworking |
Vibration |
Vibration has several parameters in common with noise-frequency, amplitude, duration of exposure and whether it is continuous or intermittent. Method of operation and skilfulness of the operator seem to play an important role in the development of harmful effects of vibration. Manual work using powered tools is associated with symptoms of peripheral circulatory disturbance known as “Raynaud's phenomenon” or “vibration-induced white fingers” (VWF). Vibrating tools may also affect the peripheral nervous system and the musculo-skeletal system with reduced grip strength, low back pain and degenerative back disorders. |
Contract machines, mining loaders, fork-lift trucks, pneumatic tools, chain saws |
Ionizing |
The most important chronic effect of ionizing radiation is cancer, including leukaemia. Overexposure from comparatively low levels of radiation have been associated with dermatitis of the hand and effects on the haematological system. Processes or activities which might give excessive exposure to ionizing radiation are very restricted and regulated. |
Nuclear reactors, medical and dental x-ray tubes, particle accelerators, radioisotopes |
Non-ionizing |
Non-ionizing radiation consists of ultraviolet radiation, visible radiation, infrared, lasers, electromagnetic fields (microwaves and radio frequency) and extreme low frequency radiation. IR radiation might cause cataracts. High-powered lasers may cause eye and skin damage. There is an increasing concern about exposure to low levels of electromagnetic fields as a cause of cancer and as a potential cause of adverse reproductive outcomes among women, especially from exposure to video display units. The question about a causal link to cancer is not yet answered. Recent reviews of available scientific knowledge generally conclude that there is no association between use of VDUs and adverse reproductive outcome. |
Ultraviolet radiation: arc welding and cutting; UV curing of inks, glues, paints, etc.; disinfection; product control |
SELF-EVALUATION QUESTIONS:
Q1. Outline the categories of hazards: describe and give examples for each class.
Source: http://www.unilus.ac.zm/Lecturer/Resources/BSPH311-FPD-2-2016-1.doc
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