Answer to Question 1
Epidemiology is the study of causal relationships between environmental factors and disease. The epidemiological theory holds that the models used for studying and determining these relationships can also be used to study causal relationships between environmental factors and accidents or diseases.
Figure 3-4 illustrates the epidemiological theory of accident causation. The key components are predispositional characteristics and situational characteristics. These characteristics, taken together, can either result in or prevent conditions that may result in an accident. For example, if an employee who is particularly susceptible to peer pressure (predisposition characteristic) is pressured by his co-workers (situational characteristic) to speed up his work, the result will be an increased probability of an accident.
Answer to Question 2
The human factors theory of accident causation attributes accidents to a chain of events ultimately caused by human error. It consists of three broad factors that lead to human error: overload, inappropriate response, and inappropriate activities. These factors are explained in the following paragraphs.
Overload
Overload amounts to an imbalance between a person's capacity at any given time and the load that person is carrying in a given state. A person's capacity is the product of such factors as his or her natural ability, training, state of mind, fatigue, stress, and physical condition. The load that a person is carrying consists of tasks for which he or she is responsible and added burdens resulting from environmental factors (noise, distractions, and so on), internal factors (personal problems, emotional stress, and worry), and situational factors (level of risk, unclear instructions, and so on). The state in which a person is acting is the product of his or her motivational arousal levels.
Inappropriate Response/Incompatibility
How a person responds in a given situation can cause or prevent an accident. If a person detects a hazardous condition but does nothing to correct it, he or she has responded inappropriately. If a person disregards an established safety procedure, he or she has responded inappropriately. Such responses can lead to accidents. In addition to inappropriate responses, this component includes tool and equipment incompatibility. The incompatibility of a person's tools and equipment with regard to size, force, reach, feel, and similar factors can lead to accidents and injuries.
Inappropriate Activities
Human error can be the result of inappropriate activities. An example of an inappropriate activity is a person who undertakes a task that he or she doesn't know how to do. Another example is a person who misjudges the degree of risk involved in a given task and proceeds based on that misjudgment. Such inappropriate activities can lead to accidents and injuries.
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